[PATCH] Implement basic threading support in the NetBSD target

[PATCH] Implement basic threading support in the NetBSD target

[Kamil Rytarowski]

Use sysctl(3) as the portable interface to prompt NetBSD threads on
all supported NetBSD versions. In future newer versions could switch
to PT_LWPSTATUS ptrace(2) API that will be supported on NetBSD 10.0
and newer.

Implement as part of nbsd_nat_target:
 - thread_name()         - read descriptive thread name
 - thread_alive()        - check whether a thread is alive
 - post_attach()         - updates the list of threads after attach
 - update_thread_list()  - updates the list of threads
 - pid_to_str()          - translates ptid to a descriptive string

There are two local static functions:
 - nbsd_thread_lister()  - generic LWP lister for a specified pid
 - nbsd_add_threads()    - utility to update the list of threads

Now, GDB on NetBSD can attach to a multithreaded process, spawn
a multithreaded process, list threads, print their LWP+PID numbers
and descriptive thread names.

gdb/ChangeLog:

       * nbsd-nat.h (struct thread_info): Add forward declaration.
       (nbsd_nat_target::thread_alive): Add.
       (nbsd_nat_target::thread_name): Likewise.
       (nbsd_nat_target::update_thread_list): Likewise.
       (update_thread_list::post_attach): Likewise.
       (post_attach::pid_to_str): Likewise.
       * nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
       (nbsd_thread_lister): Add.
       (nbsd_nat_target::thread_alive): Likewise.
       (nbsd_nat_target::thread_name): Likewise.
       (nbsd_add_threads): Likewise.
       (update_thread_list::post_attach): Likewise.
       (nbsd_nat_target::update_thread_list): Likewise.
       (post_attach::pid_to_str): Likewise.
---
 gdb/ChangeLog  |  17 ++++++
 gdb/nbsd-nat.c | 161 +++++++++++++++++++++++++++++++++++++++++++++++++
 gdb/nbsd-nat.h |   8 +++
 3 files changed, 186 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 1ee58a541cb..f31a7cf236c 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,20 @@
+2020-03-25  Kamil Rytarowski  <n54@gmx.com>
+
+	* nbsd-nat.h (struct thread_info): Add forward declaration.
+	(nbsd_nat_target::thread_alive): Add.
+	(nbsd_nat_target::thread_name): Likewise.
+	(nbsd_nat_target::update_thread_list): Likewise.
+	(update_thread_list::post_attach): Likewise.
+	(post_attach::pid_to_str): Likewise.
+	* nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
+	(nbsd_thread_lister): Add.
+	(nbsd_nat_target::thread_alive): Likewise.
+	(nbsd_nat_target::thread_name): Likewise.
+	(nbsd_add_threads): Likewise.
+	(update_thread_list::post_attach): Likewise.
+	(nbsd_nat_target::update_thread_list): Likewise.
+	(post_attach::pid_to_str): Likewise.
+
 2020-03-25  Tom Tromey  <tom@tromey.com>

 	* compile/compile-object-load.c (get_out_value_type): Mention
diff --git a/gdb/nbsd-nat.c b/gdb/nbsd-nat.c
index 326bbe3aec3..556e146ab23 100644
--- a/gdb/nbsd-nat.c
+++ b/gdb/nbsd-nat.c
@@ -20,6 +20,8 @@
 #include "defs.h"

 #include "nbsd-nat.h"
+#include "gdbthread.h"
+#include "inferior.h"

 #include <sys/types.h>
 #include <sys/ptrace.h>
@@ -39,3 +41,162 @@ nbsd_nat_target::pid_to_exec_file (int pid)
     return NULL;
   return buf;
 }
+
+/* Generic thread (LWP) lister within a specified process.  The callback
+   parameters is a C++ function that is called for each detected thread.  */
+
+static void
+nbsd_thread_lister (const pid_t pid,
+		    std::function<bool (const struct kinfo_lwp *)> callback)
+{
+  int mib[5] = {CTL_KERN, KERN_LWP, pid, sizeof (struct kinfo_lwp), 0};
+  size_t size;
+
+  if (sysctl (mib, ARRAY_SIZE (mib), NULL, &size, NULL, 0) == -1 || size == 0)
+    perror_with_name (("sysctl"));
+
+  mib[4] = size / sizeof (size_t);
+
+  gdb::unique_xmalloc_ptr<struct kinfo_lwp> kl
+    ((struct kinfo_lwp *) xcalloc (size, 1));
+  if (kl == NULL)
+    perror_with_name (("calloc"));
+
+  if (sysctl (mib, ARRAY_SIZE (mib), kl.get (), &size, NULL, 0) == -1 ||
+      size == 0)
+    perror_with_name (("sysctl"));
+
+  for (size_t i = 0; i < size / sizeof (struct kinfo_lwp); i++)
+    {
+      struct kinfo_lwp *l = &kl.get ()[i];
+
+      /* Return true if the specified thread is alive.  */
+      auto lwp_alive =
+	[&l]()
+	{
+	  switch (kl->l_stat)
+	    {
+	    case LSSLEEP:
+	    case LSRUN:
+	    case LSONPROC:
+	    case LSSTOP:
+	    case LSSUSPENDED:
+	      return true;
+	    default:
+	      return false;
+	    }
+	};
+
+      /* Ignore embryonic or demised threads.  */
+      if (!lwp_alive (l))
+	continue;
+
+      if (callback (l))
+	break;
+    }
+}
+
+/* Return true if PTID is still active in the inferior.  */
+
+bool
+nbsd_nat_target::thread_alive (ptid_t ptid)
+{
+  pid_t pid = ptid.pid ();
+  int lwp = ptid.lwp ();
+  bool found = false;
+
+  auto fn =
+    [&lwp, &found] (const struct kinfo_lwp *kl)
+    {
+      if (kl->l_lid == lwp)
+	{
+	  found = true;
+	  return true;
+	}
+      return false;
+    };
+
+  nbsd_thread_lister (pid, fn);
+
+  return found;
+}
+
+/* Return the name assigned to a thread by an application.  Returns
+   the string in a static buffer.  */
+
+const char *
+nbsd_nat_target::thread_name (struct thread_info *thr)
+{
+  ptid_t ptid = thr->ptid;
+  pid_t pid = ptid.pid ();
+  int lwp = ptid.lwp ();
+
+  static char buf[KI_LNAMELEN] = {};
+
+  auto fn =
+    [&lwp] (const struct kinfo_lwp *kl)
+    {
+      if (kl->l_lid == lwp)
+	{
+	  xsnprintf (buf, sizeof buf, "%s", kl->l_name);
+	  return true;
+	}
+      return false;
+    };
+
+  nbsd_thread_lister (pid, fn);
+
+  return buf;
+}
+
+/* Implement the "post_attach" target_ops method.  */
+
+static void
+nbsd_add_threads (nbsd_nat_target *target, pid_t pid)
+{
+  auto fn =
+    [&target, &pid] (const struct kinfo_lwp *kl)
+    {
+      ptid_t ptid = ptid_t (pid, kl->l_lid, 0);
+      fprintf_unfiltered (gdb_stdlog, "NLWP: pid=%d lwp=%d\n", pid, kl->l_lid);
+      if (!in_thread_list (target, ptid))
+	{
+	  if (inferior_ptid.lwp () == 0)
+	    thread_change_ptid (target, inferior_ptid, ptid);
+	  else
+	    add_thread (target, ptid);
+	}
+      return false;
+    };
+
+  nbsd_thread_lister (pid, fn);
+}
+
+/* Implement the "post_attach" target_ops method.  */
+
+void
+nbsd_nat_target::post_attach (int pid)
+{
+  nbsd_add_threads (this, pid);
+}
+
+/* Implement the "update_thread_list" target_ops method.  */
+
+void
+nbsd_nat_target::update_thread_list ()
+{
+  prune_threads ();
+
+  nbsd_add_threads (this, inferior_ptid.pid ());
+}
+
+/* Convert PTID to a string.  */
+
+std::string
+nbsd_nat_target::pid_to_str (ptid_t ptid)
+{
+  pid_t pid = ptid.pid ();
+  int lwp = ptid.lwp ();
+
+  return string_printf ("LWP %d of process %d", lwp, pid);
+}
diff --git a/gdb/nbsd-nat.h b/gdb/nbsd-nat.h
index a752fbe572d..3606048cd07 100644
--- a/gdb/nbsd-nat.h
+++ b/gdb/nbsd-nat.h
@@ -22,11 +22,19 @@

 #include "inf-ptrace.h"

+struct thread_info;
+
 /* A prototype NetBSD target.  */

 struct nbsd_nat_target : public inf_ptrace_target
 {
   char *pid_to_exec_file (int pid) override;
+
+  bool thread_alive (ptid_t ptid) override;
+  const char *thread_name (struct thread_info *thr) override;
+  void post_attach (int pid) override;
+  void update_thread_list () override;
+  std::string pid_to_str (ptid_t ptid) override;
 };

 #endif /* nbsd-nat.h */
--
2.25.0

[PATCH v2] Implement basic threading support in the NetBSD target

[Kamil Rytarowski]

Use sysctl(3) as the portable interface to prompt NetBSD threads on
all supported NetBSD versions. In future newer versions could switch
to PT_LWPSTATUS ptrace(2) API that will be supported on NetBSD 10.0
and newer.

Implement as part of nbsd_nat_target:
 - thread_name()         - read descriptive thread name
 - thread_alive()        - check whether a thread is alive
 - post_attach()         - updates the list of threads after attach
 - update_thread_list()  - updates the list of threads
 - pid_to_str()          - translates ptid to a descriptive string

There are two local static functions:
 - nbsd_thread_lister()  - generic LWP lister for a specified pid
 - nbsd_add_threads()    - utility to update the list of threads

Now, GDB on NetBSD can attach to a multithreaded process, spawn
a multithreaded process, list threads, print their LWP+PID numbers
and descriptive thread names.

gdb/ChangeLog:

       * nbsd-nat.h (struct thread_info): Add forward declaration.
       (nbsd_nat_target::thread_alive): Add.
       (nbsd_nat_target::thread_name): Likewise.
       (nbsd_nat_target::update_thread_list): Likewise.
       (update_thread_list::post_attach): Likewise.
       (post_attach::pid_to_str): Likewise.
       * nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
       (nbsd_thread_lister): Add.
       (nbsd_nat_target::thread_alive): Likewise.
       (nbsd_nat_target::thread_name): Likewise.
       (nbsd_add_threads): Likewise.
       (update_thread_list::post_attach): Likewise.
       (nbsd_nat_target::update_thread_list): Likewise.
       (post_attach::pid_to_str): Likewise.
---
 gdb/ChangeLog  |  17 +++++
 gdb/nbsd-nat.c | 166 +++++++++++++++++++++++++++++++++++++++++++++++++
 gdb/nbsd-nat.h |   8 +++
 3 files changed, 191 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 1ee58a541cb..f31a7cf236c 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,20 @@
+2020-03-25  Kamil Rytarowski  <n54@gmx.com>
+
+	* nbsd-nat.h (struct thread_info): Add forward declaration.
+	(nbsd_nat_target::thread_alive): Add.
+	(nbsd_nat_target::thread_name): Likewise.
+	(nbsd_nat_target::update_thread_list): Likewise.
+	(update_thread_list::post_attach): Likewise.
+	(post_attach::pid_to_str): Likewise.
+	* nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
+	(nbsd_thread_lister): Add.
+	(nbsd_nat_target::thread_alive): Likewise.
+	(nbsd_nat_target::thread_name): Likewise.
+	(nbsd_add_threads): Likewise.
+	(update_thread_list::post_attach): Likewise.
+	(nbsd_nat_target::update_thread_list): Likewise.
+	(post_attach::pid_to_str): Likewise.
+
 2020-03-25  Tom Tromey  <tom@tromey.com>

 	* compile/compile-object-load.c (get_out_value_type): Mention
diff --git a/gdb/nbsd-nat.c b/gdb/nbsd-nat.c
index 326bbe3aec3..945699ccfbe 100644
--- a/gdb/nbsd-nat.c
+++ b/gdb/nbsd-nat.c
@@ -20,6 +20,8 @@
 #include "defs.h"

 #include "nbsd-nat.h"
+#include "gdbthread.h"
+#include "inferior.h"

 #include <sys/types.h>
 #include <sys/ptrace.h>
@@ -39,3 +41,167 @@ nbsd_nat_target::pid_to_exec_file (int pid)
     return NULL;
   return buf;
 }
+
+/* Generic thread (LWP) lister within a specified process.  The callback
+   parameters is a C++ function that is called for each detected thread.  */
+
+static void
+nbsd_thread_lister (const pid_t pid,
+		    std::function<bool (const struct kinfo_lwp *)> callback)
+{
+  int mib[5] = {CTL_KERN, KERN_LWP, pid, sizeof (struct kinfo_lwp), 0};
+  size_t size;
+
+  if (sysctl (mib, ARRAY_SIZE (mib), NULL, &size, NULL, 0) == -1 || size == 0)
+    perror_with_name (("sysctl"));
+
+  mib[4] = size / sizeof (size_t);
+
+  gdb::unique_xmalloc_ptr<struct kinfo_lwp> kl
+    ((struct kinfo_lwp *) xcalloc (size, 1));
+  if (kl == NULL)
+    perror_with_name (("calloc"));
+
+  if (sysctl (mib, ARRAY_SIZE (mib), kl.get (), &size, NULL, 0) == -1 ||
+      size == 0)
+    perror_with_name (("sysctl"));
+
+  for (size_t i = 0; i < size / sizeof (struct kinfo_lwp); i++)
+    {
+      struct kinfo_lwp *l = &kl.get ()[i];
+
+      /* Return true if the specified thread is alive.  */
+      auto lwp_alive =
+	[&l]()
+	{
+	  switch (l->l_stat)
+	    {
+	    case LSSLEEP:
+	    case LSRUN:
+	    case LSONPROC:
+	    case LSSTOP:
+	    case LSSUSPENDED:
+	      return true;
+	    default:
+	      return false;
+	    }
+	};
+
+      /* Ignore embryonic or demised threads.  */
+      if (!lwp_alive ())
+	continue;
+
+      if (callback (l))
+	break;
+    }
+}
+
+/* Return true if PTID is still active in the inferior.  */
+
+bool
+nbsd_nat_target::thread_alive (ptid_t ptid)
+{
+  pid_t pid = ptid.pid ();
+  int lwp = ptid.lwp ();
+  bool found = false;
+
+  auto fn =
+    [&lwp, &found] (const struct kinfo_lwp *kl)
+    {
+      if (kl->l_lid == lwp)
+	{
+	  found = true;
+	  return true;
+	}
+      return false;
+    };
+
+  nbsd_thread_lister (pid, fn);
+
+  return found;
+}
+
+/* Return the name assigned to a thread by an application.  Returns
+   the string in a static buffer.  */
+
+const char *
+nbsd_nat_target::thread_name (struct thread_info *thr)
+{
+  ptid_t ptid = thr->ptid;
+  pid_t pid = ptid.pid ();
+  int lwp = ptid.lwp ();
+
+  static char buf[KI_LNAMELEN] = {};
+
+  auto fn =
+    [&lwp] (const struct kinfo_lwp *kl)
+    {
+      if (kl->l_lid == lwp)
+	{
+	  xsnprintf (buf, sizeof buf, "%s", kl->l_name);
+	  return true;
+	}
+      return false;
+    };
+
+  nbsd_thread_lister (pid, fn);
+
+  return buf;
+}
+
+/* Implement the "post_attach" target_ops method.  */
+
+static void
+nbsd_add_threads (nbsd_nat_target *target, pid_t pid)
+{
+  auto fn =
+    [&target, &pid] (const struct kinfo_lwp *kl)
+    {
+      ptid_t ptid = ptid_t (pid, kl->l_lid, 0);
+      if (!in_thread_list (target, ptid))
+	{
+	  if (inferior_ptid.lwp () == 0)
+	    thread_change_ptid (target, inferior_ptid, ptid);
+	  else
+	    add_thread (target, ptid);
+	}
+      return false;
+    };
+
+  nbsd_thread_lister (pid, fn);
+}
+
+/* Implement the "post_attach" target_ops method.  */
+
+void
+nbsd_nat_target::post_attach (int pid)
+{
+  nbsd_add_threads (this, pid);
+}
+
+/* Implement the "update_thread_list" target_ops method.  */
+
+void
+nbsd_nat_target::update_thread_list ()
+{
+  prune_threads ();
+
+  nbsd_add_threads (this, inferior_ptid.pid ());
+}
+
+/* Convert PTID to a string.  */
+
+std::string
+nbsd_nat_target::pid_to_str (ptid_t ptid)
+{
+  int lwp = ptid.lwp ();
+
+  if (lwp != 0)
+    {
+      pid_t pid = ptid.pid ();
+
+      return string_printf ("LWP %d of process %d", lwp, pid);
+    }
+
+  return normal_pid_to_str (ptid);
+}
diff --git a/gdb/nbsd-nat.h b/gdb/nbsd-nat.h
index a752fbe572d..3606048cd07 100644
--- a/gdb/nbsd-nat.h
+++ b/gdb/nbsd-nat.h
@@ -22,11 +22,19 @@

 #include "inf-ptrace.h"

+struct thread_info;
+
 /* A prototype NetBSD target.  */

 struct nbsd_nat_target : public inf_ptrace_target
 {
   char *pid_to_exec_file (int pid) override;
+
+  bool thread_alive (ptid_t ptid) override;
+  const char *thread_name (struct thread_info *thr) override;
+  void post_attach (int pid) override;
+  void update_thread_list () override;
+  std::string pid_to_str (ptid_t ptid) override;
 };

 #endif /* nbsd-nat.h */
--
2.25.0

Re: [PATCH v2] Implement basic threading support in the NetBSD target

[Kamil Rytarowski]

Ping?

On 26.03.2020 04:16, Kamil Rytarowski wrote:
> Use sysctl(3) as the portable interface to prompt NetBSD threads on
> all supported NetBSD versions. In future newer versions could switch
> to PT_LWPSTATUS ptrace(2) API that will be supported on NetBSD 10.0
> and newer.
>
> Implement as part of nbsd_nat_target:
>  - thread_name()         - read descriptive thread name
>  - thread_alive()        - check whether a thread is alive
>  - post_attach()         - updates the list of threads after attach
>  - update_thread_list()  - updates the list of threads
>  - pid_to_str()          - translates ptid to a descriptive string
>
> There are two local static functions:
>  - nbsd_thread_lister()  - generic LWP lister for a specified pid
>  - nbsd_add_threads()    - utility to update the list of threads
>
> Now, GDB on NetBSD can attach to a multithreaded process, spawn
> a multithreaded process, list threads, print their LWP+PID numbers
> and descriptive thread names.
>
> gdb/ChangeLog:
>
>        * nbsd-nat.h (struct thread_info): Add forward declaration.
>        (nbsd_nat_target::thread_alive): Add.
>        (nbsd_nat_target::thread_name): Likewise.
>        (nbsd_nat_target::update_thread_list): Likewise.
>        (update_thread_list::post_attach): Likewise.
>        (post_attach::pid_to_str): Likewise.
>        * nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
>        (nbsd_thread_lister): Add.
>        (nbsd_nat_target::thread_alive): Likewise.
>        (nbsd_nat_target::thread_name): Likewise.
>        (nbsd_add_threads): Likewise.
>        (update_thread_list::post_attach): Likewise.
>        (nbsd_nat_target::update_thread_list): Likewise.
>        (post_attach::pid_to_str): Likewise.
> ---
>  gdb/ChangeLog  |  17 +++++
>  gdb/nbsd-nat.c | 166 +++++++++++++++++++++++++++++++++++++++++++++++++
>  gdb/nbsd-nat.h |   8 +++
>  3 files changed, 191 insertions(+)
>
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index 1ee58a541cb..f31a7cf236c 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,3 +1,20 @@
> +2020-03-25  Kamil Rytarowski  <n54@gmx.com>
> +
> +	* nbsd-nat.h (struct thread_info): Add forward declaration.
> +	(nbsd_nat_target::thread_alive): Add.
> +	(nbsd_nat_target::thread_name): Likewise.
> +	(nbsd_nat_target::update_thread_list): Likewise.
> +	(update_thread_list::post_attach): Likewise.
> +	(post_attach::pid_to_str): Likewise.
> +	* nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
> +	(nbsd_thread_lister): Add.
> +	(nbsd_nat_target::thread_alive): Likewise.
> +	(nbsd_nat_target::thread_name): Likewise.
> +	(nbsd_add_threads): Likewise.
> +	(update_thread_list::post_attach): Likewise.
> +	(nbsd_nat_target::update_thread_list): Likewise.
> +	(post_attach::pid_to_str): Likewise.
> +
>  2020-03-25  Tom Tromey  <tom@tromey.com>
>
>  	* compile/compile-object-load.c (get_out_value_type): Mention
> diff --git a/gdb/nbsd-nat.c b/gdb/nbsd-nat.c
> index 326bbe3aec3..945699ccfbe 100644
> --- a/gdb/nbsd-nat.c
> +++ b/gdb/nbsd-nat.c
> @@ -20,6 +20,8 @@
>  #include "defs.h"
>
>  #include "nbsd-nat.h"
> +#include "gdbthread.h"
> +#include "inferior.h"
>
>  #include <sys/types.h>
>  #include <sys/ptrace.h>
> @@ -39,3 +41,167 @@ nbsd_nat_target::pid_to_exec_file (int pid)
>      return NULL;
>    return buf;
>  }
> +
> +/* Generic thread (LWP) lister within a specified process.  The callback
> +   parameters is a C++ function that is called for each detected thread.  */
> +
> +static void
> +nbsd_thread_lister (const pid_t pid,
> +		    std::function<bool (const struct kinfo_lwp *)> callback)
> +{
> +  int mib[5] = {CTL_KERN, KERN_LWP, pid, sizeof (struct kinfo_lwp), 0};
> +  size_t size;
> +
> +  if (sysctl (mib, ARRAY_SIZE (mib), NULL, &size, NULL, 0) == -1 || size == 0)
> +    perror_with_name (("sysctl"));
> +
> +  mib[4] = size / sizeof (size_t);
> +
> +  gdb::unique_xmalloc_ptr<struct kinfo_lwp> kl
> +    ((struct kinfo_lwp *) xcalloc (size, 1));
> +  if (kl == NULL)
> +    perror_with_name (("calloc"));
> +
> +  if (sysctl (mib, ARRAY_SIZE (mib), kl.get (), &size, NULL, 0) == -1 ||
> +      size == 0)
> +    perror_with_name (("sysctl"));
> +
> +  for (size_t i = 0; i < size / sizeof (struct kinfo_lwp); i++)
> +    {
> +      struct kinfo_lwp *l = &kl.get ()[i];
> +
> +      /* Return true if the specified thread is alive.  */
> +      auto lwp_alive =
> +	[&l]()
> +	{
> +	  switch (l->l_stat)
> +	    {
> +	    case LSSLEEP:
> +	    case LSRUN:
> +	    case LSONPROC:
> +	    case LSSTOP:
> +	    case LSSUSPENDED:
> +	      return true;
> +	    default:
> +	      return false;
> +	    }
> +	};
> +
> +      /* Ignore embryonic or demised threads.  */
> +      if (!lwp_alive ())
> +	continue;
> +
> +      if (callback (l))
> +	break;
> +    }
> +}
> +
> +/* Return true if PTID is still active in the inferior.  */
> +
> +bool
> +nbsd_nat_target::thread_alive (ptid_t ptid)
> +{
> +  pid_t pid = ptid.pid ();
> +  int lwp = ptid.lwp ();
> +  bool found = false;
> +
> +  auto fn =
> +    [&lwp, &found] (const struct kinfo_lwp *kl)
> +    {
> +      if (kl->l_lid == lwp)
> +	{
> +	  found = true;
> +	  return true;
> +	}
> +      return false;
> +    };
> +
> +  nbsd_thread_lister (pid, fn);
> +
> +  return found;
> +}
> +
> +/* Return the name assigned to a thread by an application.  Returns
> +   the string in a static buffer.  */
> +
> +const char *
> +nbsd_nat_target::thread_name (struct thread_info *thr)
> +{
> +  ptid_t ptid = thr->ptid;
> +  pid_t pid = ptid.pid ();
> +  int lwp = ptid.lwp ();
> +
> +  static char buf[KI_LNAMELEN] = {};
> +
> +  auto fn =
> +    [&lwp] (const struct kinfo_lwp *kl)
> +    {
> +      if (kl->l_lid == lwp)
> +	{
> +	  xsnprintf (buf, sizeof buf, "%s", kl->l_name);
> +	  return true;
> +	}
> +      return false;
> +    };
> +
> +  nbsd_thread_lister (pid, fn);
> +
> +  return buf;
> +}
> +
> +/* Implement the "post_attach" target_ops method.  */
> +
> +static void
> +nbsd_add_threads (nbsd_nat_target *target, pid_t pid)
> +{
> +  auto fn =
> +    [&target, &pid] (const struct kinfo_lwp *kl)
> +    {
> +      ptid_t ptid = ptid_t (pid, kl->l_lid, 0);
> +      if (!in_thread_list (target, ptid))
> +	{
> +	  if (inferior_ptid.lwp () == 0)
> +	    thread_change_ptid (target, inferior_ptid, ptid);
> +	  else
> +	    add_thread (target, ptid);
> +	}
> +      return false;
> +    };
> +
> +  nbsd_thread_lister (pid, fn);
> +}
> +
> +/* Implement the "post_attach" target_ops method.  */
> +
> +void
> +nbsd_nat_target::post_attach (int pid)
> +{
> +  nbsd_add_threads (this, pid);
> +}
> +
> +/* Implement the "update_thread_list" target_ops method.  */
> +
> +void
> +nbsd_nat_target::update_thread_list ()
> +{
> +  prune_threads ();
> +
> +  nbsd_add_threads (this, inferior_ptid.pid ());
> +}
> +
> +/* Convert PTID to a string.  */
> +
> +std::string
> +nbsd_nat_target::pid_to_str (ptid_t ptid)
> +{
> +  int lwp = ptid.lwp ();
> +
> +  if (lwp != 0)
> +    {
> +      pid_t pid = ptid.pid ();
> +
> +      return string_printf ("LWP %d of process %d", lwp, pid);
> +    }
> +
> +  return normal_pid_to_str (ptid);
> +}
> diff --git a/gdb/nbsd-nat.h b/gdb/nbsd-nat.h
> index a752fbe572d..3606048cd07 100644
> --- a/gdb/nbsd-nat.h
> +++ b/gdb/nbsd-nat.h
> @@ -22,11 +22,19 @@
>
>  #include "inf-ptrace.h"
>
> +struct thread_info;
> +
>  /* A prototype NetBSD target.  */
>
>  struct nbsd_nat_target : public inf_ptrace_target
>  {
>    char *pid_to_exec_file (int pid) override;
> +
> +  bool thread_alive (ptid_t ptid) override;
> +  const char *thread_name (struct thread_info *thr) override;
> +  void post_attach (int pid) override;
> +  void update_thread_list () override;
> +  std::string pid_to_str (ptid_t ptid) override;
>  };
>
>  #endif /* nbsd-nat.h */
> --
> 2.25.0
>

Re: [PATCH v2] Implement basic threading support in the NetBSD target

[Tom Tromey]

>>>>> "Kamil" == Kamil Rytarowski <n54@gmx.com> writes:

Kamil> +  auto fn =
Kamil> +    [&lwp, &found] (const struct kinfo_lwp *kl)

Also, in the gdb style, "=" is an operator and goes after the line
break.  There were a few instances of this.

Tom

Re: [PATCH v2] Implement basic threading support in the NetBSD target

[Kamil Rytarowski]

On 01.04.2020 22:44, Tom Tromey wrote:
>>>>>> "Kamil" == Kamil Rytarowski <n54@gmx.com> writes:
>
> Kamil> +  auto fn =
> Kamil> +    [&lwp, &found] (const struct kinfo_lwp *kl)
>
> Also, in the gdb style, "=" is an operator and goes after the line
> break.  There were a few instances of this.
>
> Tom
>

Fixed in:

[PATCH v3] Implement basic threading support in the NetBSD target

[PATCH v3] Implement basic threading support in the NetBSD target

[Kamil Rytarowski]

Use sysctl(3) as the portable interface to prompt NetBSD threads on
all supported NetBSD versions. In future newer versions could switch
to PT_LWPSTATUS ptrace(2) API that will be supported on NetBSD 10.0
and newer.

Implement as part of nbsd_nat_target:
 - thread_name()         - read descriptive thread name
 - thread_alive()        - check whether a thread is alive
 - post_attach()         - updates the list of threads after attach
 - update_thread_list()  - updates the list of threads
 - pid_to_str()          - translates ptid to a descriptive string

There are two local static functions:
 - nbsd_thread_lister()  - generic LWP lister for a specified pid
 - nbsd_add_threads()    - utility to update the list of threads

Now, GDB on NetBSD can attach to a multithreaded process, spawn
a multithreaded process, list threads, print their LWP+PID numbers
and descriptive thread names.

gdb/ChangeLog:

       * nbsd-nat.h (struct thread_info): Add forward declaration.
       (nbsd_nat_target::thread_alive): Add.
       (nbsd_nat_target::thread_name): Likewise.
       (nbsd_nat_target::update_thread_list): Likewise.
       (update_thread_list::post_attach): Likewise.
       (post_attach::pid_to_str): Likewise.
       * nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
       (nbsd_thread_lister): Add.
       (nbsd_nat_target::thread_alive): Likewise.
       (nbsd_nat_target::thread_name): Likewise.
       (nbsd_add_threads): Likewise.
       (update_thread_list::post_attach): Likewise.
       (nbsd_nat_target::update_thread_list): Likewise.
       (post_attach::pid_to_str): Likewise.
---
 gdb/ChangeLog  |  17 +++++
 gdb/nbsd-nat.c | 166 +++++++++++++++++++++++++++++++++++++++++++++++++
 gdb/nbsd-nat.h |   8 +++
 3 files changed, 191 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index ef62216e0ad..764b65d872d 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,20 @@
+2020-04-01  Kamil Rytarowski  <n54@gmx.com>
+
+	* nbsd-nat.h (struct thread_info): Add forward declaration.
+	(nbsd_nat_target::thread_alive): Add.
+	(nbsd_nat_target::thread_name): Likewise.
+	(nbsd_nat_target::update_thread_list): Likewise.
+	(update_thread_list::post_attach): Likewise.
+	(post_attach::pid_to_str): Likewise.
+	* nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
+	(nbsd_thread_lister): Add.
+	(nbsd_nat_target::thread_alive): Likewise.
+	(nbsd_nat_target::thread_name): Likewise.
+	(nbsd_add_threads): Likewise.
+	(update_thread_list::post_attach): Likewise.
+	(nbsd_nat_target::update_thread_list): Likewise.
+	(post_attach::pid_to_str): Likewise.
+
 2020-04-01  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

 	* infrun.c (stop_all_threads): Update assertion, plus when
diff --git a/gdb/nbsd-nat.c b/gdb/nbsd-nat.c
index 326bbe3aec3..54ae172ba7c 100644
--- a/gdb/nbsd-nat.c
+++ b/gdb/nbsd-nat.c
@@ -20,6 +20,8 @@
 #include "defs.h"

 #include "nbsd-nat.h"
+#include "gdbthread.h"
+#include "inferior.h"

 #include <sys/types.h>
 #include <sys/ptrace.h>
@@ -39,3 +41,167 @@ nbsd_nat_target::pid_to_exec_file (int pid)
     return NULL;
   return buf;
 }
+
+/* Generic thread (LWP) lister within a specified process.  The callback
+   parameters is a C++ function that is called for each detected thread.  */
+
+static void
+nbsd_thread_lister (const pid_t pid,
+		    std::function<bool (const struct kinfo_lwp *)> callback)
+{
+  int mib[5] = {CTL_KERN, KERN_LWP, pid, sizeof (struct kinfo_lwp), 0};
+  size_t size;
+
+  if (sysctl (mib, ARRAY_SIZE (mib), NULL, &size, NULL, 0) == -1 || size == 0)
+    perror_with_name (("sysctl"));
+
+  mib[4] = size / sizeof (size_t);
+
+  gdb::unique_xmalloc_ptr<struct kinfo_lwp> kl
+    ((struct kinfo_lwp *) xcalloc (size, 1));
+  if (kl == NULL)
+    perror_with_name (("calloc"));
+
+  if (sysctl (mib, ARRAY_SIZE (mib), kl.get (), &size, NULL, 0) == -1
+      || size == 0)
+    perror_with_name (("sysctl"));
+
+  for (size_t i = 0; i < size / sizeof (struct kinfo_lwp); i++)
+    {
+      struct kinfo_lwp *l = &kl.get ()[i];
+
+      /* Return true if the specified thread is alive.  */
+      auto lwp_alive
+	= [](struct kinfo_lwp *lwp)
+	  {
+	    switch (lwp->l_stat)
+	      {
+	      case LSSLEEP:
+	      case LSRUN:
+	      case LSONPROC:
+	      case LSSTOP:
+	      case LSSUSPENDED:
+		return true;
+	      default:
+		return false;
+	      }
+	  };
+
+      /* Ignore embryonic or demised threads.  */
+      if (!lwp_alive (l))
+	continue;
+
+      if (callback (l))
+	break;
+    }
+}
+
+/* Return true if PTID is still active in the inferior.  */
+
+bool
+nbsd_nat_target::thread_alive (ptid_t ptid)
+{
+  pid_t pid = ptid.pid ();
+  int lwp = ptid.lwp ();
+  bool found = false;
+
+  auto fn
+    = [&lwp, &found] (const struct kinfo_lwp *kl)
+      {
+	if (kl->l_lid == lwp)
+	  {
+	    found = true;
+	    return true;
+	  }
+	return false;
+      };
+
+  nbsd_thread_lister (pid, fn);
+
+  return found;
+}
+
+/* Return the name assigned to a thread by an application.  Returns
+   the string in a static buffer.  */
+
+const char *
+nbsd_nat_target::thread_name (struct thread_info *thr)
+{
+  ptid_t ptid = thr->ptid;
+  pid_t pid = ptid.pid ();
+  int lwp = ptid.lwp ();
+
+  static char buf[KI_LNAMELEN] = {};
+
+  auto fn
+    = [&lwp] (const struct kinfo_lwp *kl)
+      {
+	if (kl->l_lid == lwp)
+	  {
+	    xsnprintf (buf, sizeof buf, "%s", kl->l_name);
+	    return true;
+	  }
+	return false;
+      };
+
+  nbsd_thread_lister (pid, fn);
+
+  return buf;
+}
+
+/* Implement the "post_attach" target_ops method.  */
+
+static void
+nbsd_add_threads (nbsd_nat_target *target, pid_t pid)
+{
+  auto fn
+    = [&target, &pid] (const struct kinfo_lwp *kl)
+      {
+	ptid_t ptid = ptid_t (pid, kl->l_lid, 0);
+	if (!in_thread_list (target, ptid))
+	  {
+	    if (inferior_ptid.lwp () == 0)
+	      thread_change_ptid (target, inferior_ptid, ptid);
+	    else
+	      add_thread (target, ptid);
+	  }
+	return false;
+      };
+
+  nbsd_thread_lister (pid, fn);
+}
+
+/* Implement the "post_attach" target_ops method.  */
+
+void
+nbsd_nat_target::post_attach (int pid)
+{
+  nbsd_add_threads (this, pid);
+}
+
+/* Implement the "update_thread_list" target_ops method.  */
+
+void
+nbsd_nat_target::update_thread_list ()
+{
+  prune_threads ();
+
+  nbsd_add_threads (this, inferior_ptid.pid ());
+}
+
+/* Convert PTID to a string.  */
+
+std::string
+nbsd_nat_target::pid_to_str (ptid_t ptid)
+{
+  int lwp = ptid.lwp ();
+
+  if (lwp != 0)
+    {
+      pid_t pid = ptid.pid ();
+
+      return string_printf ("LWP %d of process %d", lwp, pid);
+    }
+
+  return normal_pid_to_str (ptid);
+}
diff --git a/gdb/nbsd-nat.h b/gdb/nbsd-nat.h
index a752fbe572d..3606048cd07 100644
--- a/gdb/nbsd-nat.h
+++ b/gdb/nbsd-nat.h
@@ -22,11 +22,19 @@

 #include "inf-ptrace.h"

+struct thread_info;
+
 /* A prototype NetBSD target.  */

 struct nbsd_nat_target : public inf_ptrace_target
 {
   char *pid_to_exec_file (int pid) override;
+
+  bool thread_alive (ptid_t ptid) override;
+  const char *thread_name (struct thread_info *thr) override;
+  void post_attach (int pid) override;
+  void update_thread_list () override;
+  std::string pid_to_str (ptid_t ptid) override;
 };

 #endif /* nbsd-nat.h */
--
2.25.0

[PATCH v4] Implement basic threading support in the NetBSD target

[Kamil Rytarowski]

Use sysctl(3) as the portable interface to prompt NetBSD threads on
all supported NetBSD versions. In future newer versions could switch
to PT_LWPSTATUS ptrace(2) API that will be supported on NetBSD 10.0
and newer.

Implement as part of nbsd_nat_target:
 - thread_name()         - read descriptive thread name
 - thread_alive()        - check whether a thread is alive
 - post_attach()         - updates the list of threads after attach
 - update_thread_list()  - updates the list of threads
 - pid_to_str()          - translates ptid to a descriptive string

There are two local static functions:
 - nbsd_thread_lister()  - generic LWP lister for a specified pid
 - nbsd_add_threads()    - utility to update the list of threads

Now, GDB on NetBSD can attach to a multithreaded process, spawn
a multithreaded process, list threads, print their LWP+PID numbers
and descriptive thread names.

gdb/ChangeLog:

       * nbsd-nat.h (struct thread_info): Add forward declaration.
       (nbsd_nat_target::thread_alive): Add.
       (nbsd_nat_target::thread_name): Likewise.
       (nbsd_nat_target::update_thread_list): Likewise.
       (update_thread_list::post_attach): Likewise.
       (post_attach::pid_to_str): Likewise.
       * nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
       (nbsd_thread_lister): Add.
       (nbsd_nat_target::thread_alive): Likewise.
       (nbsd_nat_target::thread_name): Likewise.
       (nbsd_add_threads): Likewise.
       (update_thread_list::post_attach): Likewise.
       (nbsd_nat_target::update_thread_list): Likewise.
       (post_attach::pid_to_str): Likewise.
---
 gdb/ChangeLog  |  17 ++++++
 gdb/nbsd-nat.c | 162 +++++++++++++++++++++++++++++++++++++++++++++++++
 gdb/nbsd-nat.h |   8 +++
 3 files changed, 187 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index ef62216e0ad..764b65d872d 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,20 @@
+2020-04-01  Kamil Rytarowski  <n54@gmx.com>
+
+	* nbsd-nat.h (struct thread_info): Add forward declaration.
+	(nbsd_nat_target::thread_alive): Add.
+	(nbsd_nat_target::thread_name): Likewise.
+	(nbsd_nat_target::update_thread_list): Likewise.
+	(update_thread_list::post_attach): Likewise.
+	(post_attach::pid_to_str): Likewise.
+	* nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
+	(nbsd_thread_lister): Add.
+	(nbsd_nat_target::thread_alive): Likewise.
+	(nbsd_nat_target::thread_name): Likewise.
+	(nbsd_add_threads): Likewise.
+	(update_thread_list::post_attach): Likewise.
+	(nbsd_nat_target::update_thread_list): Likewise.
+	(post_attach::pid_to_str): Likewise.
+
 2020-04-01  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

 	* infrun.c (stop_all_threads): Update assertion, plus when
diff --git a/gdb/nbsd-nat.c b/gdb/nbsd-nat.c
index 326bbe3aec3..e5510312ed1 100644
--- a/gdb/nbsd-nat.c
+++ b/gdb/nbsd-nat.c
@@ -20,6 +20,8 @@
 #include "defs.h"

 #include "nbsd-nat.h"
+#include "gdbthread.h"
+#include "inferior.h"

 #include <sys/types.h>
 #include <sys/ptrace.h>
@@ -39,3 +41,163 @@ nbsd_nat_target::pid_to_exec_file (int pid)
     return NULL;
   return buf;
 }
+
+/* Generic thread (LWP) lister within a specified process.  The callback
+   parameters is a C++ function that is called for each detected thread.  */
+
+static bool
+nbsd_thread_lister (const pid_t pid,
+		    gdb::function_view<bool (const struct kinfo_lwp *)>
+		    callback)
+{
+  int mib[5] = {CTL_KERN, KERN_LWP, pid, sizeof (struct kinfo_lwp), 0};
+  size_t size;
+
+  if (sysctl (mib, ARRAY_SIZE (mib), NULL, &size, NULL, 0) == -1 || size == 0)
+    perror_with_name (("sysctl"));
+
+  mib[4] = size / sizeof (size_t);
+
+  gdb::unique_xmalloc_ptr<struct kinfo_lwp> kl
+    ((struct kinfo_lwp *) xcalloc (size, 1));
+  if (kl == NULL)
+    perror_with_name (("calloc"));
+
+  if (sysctl (mib, ARRAY_SIZE (mib), kl.get (), &size, NULL, 0) == -1
+      || size == 0)
+    perror_with_name (("sysctl"));
+
+  for (size_t i = 0; i < size / sizeof (struct kinfo_lwp); i++)
+    {
+      struct kinfo_lwp *l = &kl.get ()[i];
+
+      /* Return true if the specified thread is alive.  */
+      auto lwp_alive
+	= [] (struct kinfo_lwp *lwp)
+	  {
+	    switch (lwp->l_stat)
+	      {
+	      case LSSLEEP:
+	      case LSRUN:
+	      case LSONPROC:
+	      case LSSTOP:
+	      case LSSUSPENDED:
+		return true;
+	      default:
+		return false;
+	      }
+	  };
+
+      /* Ignore embryonic or demised threads.  */
+      if (!lwp_alive (l))
+	continue;
+
+      if (callback (l))
+	return true;
+    }
+
+  return false;
+}
+
+/* Return true if PTID is still active in the inferior.  */
+
+bool
+nbsd_nat_target::thread_alive (ptid_t ptid)
+{
+  pid_t pid = ptid.pid ();
+  int lwp = ptid.lwp ();
+
+  auto fn
+    = [&lwp] (const struct kinfo_lwp *kl)
+      {
+        return kl->l_lid == lwp;
+      };
+
+  return nbsd_thread_lister (pid, fn);
+}
+
+/* Return the name assigned to a thread by an application.  Returns
+   the string in a static buffer.  */
+
+const char *
+nbsd_nat_target::thread_name (struct thread_info *thr)
+{
+  ptid_t ptid = thr->ptid;
+  pid_t pid = ptid.pid ();
+  int lwp = ptid.lwp ();
+
+  static char buf[KI_LNAMELEN] = {};
+
+  auto fn
+    = [&lwp] (const struct kinfo_lwp *kl)
+      {
+	if (kl->l_lid == lwp)
+	  {
+	    xsnprintf (buf, sizeof buf, "%s", kl->l_name);
+	    return true;
+	  }
+	return false;
+      };
+
+  if (nbsd_thread_lister (pid, fn))
+    return buf;
+  else
+    return NULL;
+}
+
+/* Implement the "post_attach" target_ops method.  */
+
+static void
+nbsd_add_threads (nbsd_nat_target *target, pid_t pid)
+{
+  auto fn
+    = [&target, &pid] (const struct kinfo_lwp *kl)
+      {
+	ptid_t ptid = ptid_t (pid, kl->l_lid, 0);
+	if (!in_thread_list (target, ptid))
+	  {
+	    if (inferior_ptid.lwp () == 0)
+	      thread_change_ptid (target, inferior_ptid, ptid);
+	    else
+	      add_thread (target, ptid);
+	  }
+	return false;
+      };
+
+  nbsd_thread_lister (pid, fn);
+}
+
+/* Implement the "post_attach" target_ops method.  */
+
+void
+nbsd_nat_target::post_attach (int pid)
+{
+  nbsd_add_threads (this, pid);
+}
+
+/* Implement the "update_thread_list" target_ops method.  */
+
+void
+nbsd_nat_target::update_thread_list ()
+{
+  prune_threads ();
+
+  nbsd_add_threads (this, inferior_ptid.pid ());
+}
+
+/* Convert PTID to a string.  */
+
+std::string
+nbsd_nat_target::pid_to_str (ptid_t ptid)
+{
+  int lwp = ptid.lwp ();
+
+  if (lwp != 0)
+    {
+      pid_t pid = ptid.pid ();
+
+      return string_printf ("LWP %d of process %d", lwp, pid);
+    }
+
+  return normal_pid_to_str (ptid);
+}
diff --git a/gdb/nbsd-nat.h b/gdb/nbsd-nat.h
index a752fbe572d..3606048cd07 100644
--- a/gdb/nbsd-nat.h
+++ b/gdb/nbsd-nat.h
@@ -22,11 +22,19 @@

 #include "inf-ptrace.h"

+struct thread_info;
+
 /* A prototype NetBSD target.  */

 struct nbsd_nat_target : public inf_ptrace_target
 {
   char *pid_to_exec_file (int pid) override;
+
+  bool thread_alive (ptid_t ptid) override;
+  const char *thread_name (struct thread_info *thr) override;
+  void post_attach (int pid) override;
+  void update_thread_list () override;
+  std::string pid_to_str (ptid_t ptid) override;
 };

 #endif /* nbsd-nat.h */
--
2.25.0

Re: [PATCH v4] Implement basic threading support in the NetBSD target

[Pedro Alves]

Hi,

I skimmed the patch and noticed a couple nits.

On 4/1/20 10:33 PM, Kamil Rytarowski wrote:

> +static bool
> +nbsd_thread_lister (const pid_t pid,
> +		    gdb::function_view<bool (const struct kinfo_lwp *)>
> +		    callback)
> +{
> +  int mib[5] = {CTL_KERN, KERN_LWP, pid, sizeof (struct kinfo_lwp), 0};
> +  size_t size;
> +
> +  if (sysctl (mib, ARRAY_SIZE (mib), NULL, &size, NULL, 0) == -1 || size == 0)
> +    perror_with_name (("sysctl"));
> +
> +  mib[4] = size / sizeof (size_t);
> +
> +  gdb::unique_xmalloc_ptr<struct kinfo_lwp> kl

You can use the array variant:

 gdb::unique_xmalloc_ptr<struct kinfo_lwp[]>

> +    ((struct kinfo_lwp *) xcalloc (size, 1));
> +  if (kl == NULL)
> +    perror_with_name (("calloc"));

xcalloc doesn't ever return NULL.

> +
> +  if (sysctl (mib, ARRAY_SIZE (mib), kl.get (), &size, NULL, 0) == -1
> +      || size == 0)
> +    perror_with_name (("sysctl"));
> +
> +  for (size_t i = 0; i < size / sizeof (struct kinfo_lwp); i++)
> +    {
> +      struct kinfo_lwp *l = &kl.get ()[i];

If you use the array variant, then here you don't need the .get(), like:

      struct kinfo_lwp *l = &kl[i];

Thanks,
Pedro Alves

Re: [PATCH v4] Implement basic threading support in the NetBSD target

[Kamil Rytarowski]

On 02.04.2020 21:05, Pedro Alves wrote:
> Hi,
>
> I skimmed the patch and noticed a couple nits.
>
> On 4/1/20 10:33 PM, Kamil Rytarowski wrote:
>
>> +static bool
>> +nbsd_thread_lister (const pid_t pid,
>> +		    gdb::function_view<bool (const struct kinfo_lwp *)>
>> +		    callback)
>> +{
>> +  int mib[5] = {CTL_KERN, KERN_LWP, pid, sizeof (struct kinfo_lwp), 0};
>> +  size_t size;
>> +
>> +  if (sysctl (mib, ARRAY_SIZE (mib), NULL, &size, NULL, 0) == -1 || size == 0)
>> +    perror_with_name (("sysctl"));
>> +
>> +  mib[4] = size / sizeof (size_t);
>> +
>> +  gdb::unique_xmalloc_ptr<struct kinfo_lwp> kl
>
> You can use the array variant:
>
>  gdb::unique_xmalloc_ptr<struct kinfo_lwp[]>
>

Done.

>> +    ((struct kinfo_lwp *) xcalloc (size, 1));
>> +  if (kl == NULL)
>> +    perror_with_name (("calloc"));
>
> xcalloc doesn't ever return NULL.
>

Done.

>> +
>> +  if (sysctl (mib, ARRAY_SIZE (mib), kl.get (), &size, NULL, 0) == -1
>> +      || size == 0)
>> +    perror_with_name (("sysctl"));
>> +
>> +  for (size_t i = 0; i < size / sizeof (struct kinfo_lwp); i++)
>> +    {
>> +      struct kinfo_lwp *l = &kl.get ()[i];
>
> If you use the array variant, then here you don't need the .get(), like:
>
>       struct kinfo_lwp *l = &kl[i];
>

Done.

> Thanks,
> Pedro Alves
>

Please see v5.

[PATCH v5] Implement basic threading support in the NetBSD target

[Kamil Rytarowski]

Use sysctl(3) as the portable interface to prompt NetBSD threads on
all supported NetBSD versions. In future newer versions could switch
to PT_LWPSTATUS ptrace(2) API that will be supported on NetBSD 10.0
and newer.

Implement as part of nbsd_nat_target:
 - thread_name()         - read descriptive thread name
 - thread_alive()        - check whether a thread is alive
 - post_attach()         - updates the list of threads after attach
 - update_thread_list()  - updates the list of threads
 - pid_to_str()          - translates ptid to a descriptive string

There are two local static functions:
 - nbsd_thread_lister()  - generic LWP lister for a specified pid
 - nbsd_add_threads()    - utility to update the list of threads

Now, GDB on NetBSD can attach to a multithreaded process, spawn
a multithreaded process, list threads, print their LWP+PID numbers
and descriptive thread names.

gdb/ChangeLog:

       * nbsd-nat.h (struct thread_info): Add forward declaration.
       (nbsd_nat_target::thread_alive): Add.
       (nbsd_nat_target::thread_name): Likewise.
       (nbsd_nat_target::update_thread_list): Likewise.
       (update_thread_list::post_attach): Likewise.
       (post_attach::pid_to_str): Likewise.
       * nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
       (nbsd_thread_lister): Add.
       (nbsd_nat_target::thread_alive): Likewise.
       (nbsd_nat_target::thread_name): Likewise.
       (nbsd_add_threads): Likewise.
       (update_thread_list::post_attach): Likewise.
       (nbsd_nat_target::update_thread_list): Likewise.
       (post_attach::pid_to_str): Likewise.
---
 gdb/ChangeLog  |  17 ++++++
 gdb/nbsd-nat.c | 160 +++++++++++++++++++++++++++++++++++++++++++++++++
 gdb/nbsd-nat.h |   8 +++
 3 files changed, 185 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index ef62216e0ad..764b65d872d 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,20 @@
+2020-04-01  Kamil Rytarowski  <n54@gmx.com>
+
+	* nbsd-nat.h (struct thread_info): Add forward declaration.
+	(nbsd_nat_target::thread_alive): Add.
+	(nbsd_nat_target::thread_name): Likewise.
+	(nbsd_nat_target::update_thread_list): Likewise.
+	(update_thread_list::post_attach): Likewise.
+	(post_attach::pid_to_str): Likewise.
+	* nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
+	(nbsd_thread_lister): Add.
+	(nbsd_nat_target::thread_alive): Likewise.
+	(nbsd_nat_target::thread_name): Likewise.
+	(nbsd_add_threads): Likewise.
+	(update_thread_list::post_attach): Likewise.
+	(nbsd_nat_target::update_thread_list): Likewise.
+	(post_attach::pid_to_str): Likewise.
+
 2020-04-01  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

 	* infrun.c (stop_all_threads): Update assertion, plus when
diff --git a/gdb/nbsd-nat.c b/gdb/nbsd-nat.c
index 326bbe3aec3..4423e19428d 100644
--- a/gdb/nbsd-nat.c
+++ b/gdb/nbsd-nat.c
@@ -20,6 +20,8 @@
 #include "defs.h"

 #include "nbsd-nat.h"
+#include "gdbthread.h"
+#include "inferior.h"

 #include <sys/types.h>
 #include <sys/ptrace.h>
@@ -39,3 +41,161 @@ nbsd_nat_target::pid_to_exec_file (int pid)
     return NULL;
   return buf;
 }
+
+/* Generic thread (LWP) lister within a specified process.  The callback
+   parameters is a C++ function that is called for each detected thread.  */
+
+static bool
+nbsd_thread_lister (const pid_t pid,
+		    gdb::function_view<bool (const struct kinfo_lwp *)>
+		    callback)
+{
+  int mib[5] = {CTL_KERN, KERN_LWP, pid, sizeof (struct kinfo_lwp), 0};
+  size_t size;
+
+  if (sysctl (mib, ARRAY_SIZE (mib), NULL, &size, NULL, 0) == -1 || size == 0)
+    perror_with_name (("sysctl"));
+
+  mib[4] = size / sizeof (size_t);
+
+  gdb::unique_xmalloc_ptr<struct kinfo_lwp[]> kl
+    ((struct kinfo_lwp *) xcalloc (size, 1));
+
+  if (sysctl (mib, ARRAY_SIZE (mib), kl.get (), &size, NULL, 0) == -1
+      || size == 0)
+    perror_with_name (("sysctl"));
+
+  for (size_t i = 0; i < size / sizeof (struct kinfo_lwp); i++)
+    {
+      struct kinfo_lwp *l = &kl[i];
+
+      /* Return true if the specified thread is alive.  */
+      auto lwp_alive
+	= [] (struct kinfo_lwp *lwp)
+	  {
+	    switch (lwp->l_stat)
+	      {
+	      case LSSLEEP:
+	      case LSRUN:
+	      case LSONPROC:
+	      case LSSTOP:
+	      case LSSUSPENDED:
+		return true;
+	      default:
+		return false;
+	      }
+	  };
+
+      /* Ignore embryonic or demised threads.  */
+      if (!lwp_alive (l))
+	continue;
+
+      if (callback (l))
+	return true;
+    }
+
+  return false;
+}
+
+/* Return true if PTID is still active in the inferior.  */
+
+bool
+nbsd_nat_target::thread_alive (ptid_t ptid)
+{
+  pid_t pid = ptid.pid ();
+  int lwp = ptid.lwp ();
+
+  auto fn
+    = [&lwp] (const struct kinfo_lwp *kl)
+      {
+        return kl->l_lid == lwp;
+      };
+
+  return nbsd_thread_lister (pid, fn);
+}
+
+/* Return the name assigned to a thread by an application.  Returns
+   the string in a static buffer.  */
+
+const char *
+nbsd_nat_target::thread_name (struct thread_info *thr)
+{
+  ptid_t ptid = thr->ptid;
+  pid_t pid = ptid.pid ();
+  int lwp = ptid.lwp ();
+
+  static char buf[KI_LNAMELEN] = {};
+
+  auto fn
+    = [&lwp] (const struct kinfo_lwp *kl)
+      {
+	if (kl->l_lid == lwp)
+	  {
+	    xsnprintf (buf, sizeof buf, "%s", kl->l_name);
+	    return true;
+	  }
+	return false;
+      };
+
+  if (nbsd_thread_lister (pid, fn))
+    return buf;
+  else
+    return NULL;
+}
+
+/* Implement the "post_attach" target_ops method.  */
+
+static void
+nbsd_add_threads (nbsd_nat_target *target, pid_t pid)
+{
+  auto fn
+    = [&target, &pid] (const struct kinfo_lwp *kl)
+      {
+	ptid_t ptid = ptid_t (pid, kl->l_lid, 0);
+	if (!in_thread_list (target, ptid))
+	  {
+	    if (inferior_ptid.lwp () == 0)
+	      thread_change_ptid (target, inferior_ptid, ptid);
+	    else
+	      add_thread (target, ptid);
+	  }
+	return false;
+      };
+
+  nbsd_thread_lister (pid, fn);
+}
+
+/* Implement the "post_attach" target_ops method.  */
+
+void
+nbsd_nat_target::post_attach (int pid)
+{
+  nbsd_add_threads (this, pid);
+}
+
+/* Implement the "update_thread_list" target_ops method.  */
+
+void
+nbsd_nat_target::update_thread_list ()
+{
+  prune_threads ();
+
+  nbsd_add_threads (this, inferior_ptid.pid ());
+}
+
+/* Convert PTID to a string.  */
+
+std::string
+nbsd_nat_target::pid_to_str (ptid_t ptid)
+{
+  int lwp = ptid.lwp ();
+
+  if (lwp != 0)
+    {
+      pid_t pid = ptid.pid ();
+
+      return string_printf ("LWP %d of process %d", lwp, pid);
+    }
+
+  return normal_pid_to_str (ptid);
+}
diff --git a/gdb/nbsd-nat.h b/gdb/nbsd-nat.h
index a752fbe572d..3606048cd07 100644
--- a/gdb/nbsd-nat.h
+++ b/gdb/nbsd-nat.h
@@ -22,11 +22,19 @@

 #include "inf-ptrace.h"

+struct thread_info;
+
 /* A prototype NetBSD target.  */

 struct nbsd_nat_target : public inf_ptrace_target
 {
   char *pid_to_exec_file (int pid) override;
+
+  bool thread_alive (ptid_t ptid) override;
+  const char *thread_name (struct thread_info *thr) override;
+  void post_attach (int pid) override;
+  void update_thread_list () override;
+  std::string pid_to_str (ptid_t ptid) override;
 };

 #endif /* nbsd-nat.h */
--
2.25.0

Re: [PATCH v5] Implement basic threading support in the NetBSD target

[Kamil Rytarowski]

Ping?

On 02.04.2020 21:24, Kamil Rytarowski wrote:
> Use sysctl(3) as the portable interface to prompt NetBSD threads on
> all supported NetBSD versions. In future newer versions could switch
> to PT_LWPSTATUS ptrace(2) API that will be supported on NetBSD 10.0
> and newer.
>
> Implement as part of nbsd_nat_target:
>  - thread_name()         - read descriptive thread name
>  - thread_alive()        - check whether a thread is alive
>  - post_attach()         - updates the list of threads after attach
>  - update_thread_list()  - updates the list of threads
>  - pid_to_str()          - translates ptid to a descriptive string
>
> There are two local static functions:
>  - nbsd_thread_lister()  - generic LWP lister for a specified pid
>  - nbsd_add_threads()    - utility to update the list of threads
>
> Now, GDB on NetBSD can attach to a multithreaded process, spawn
> a multithreaded process, list threads, print their LWP+PID numbers
> and descriptive thread names.
>
> gdb/ChangeLog:
>
>        * nbsd-nat.h (struct thread_info): Add forward declaration.
>        (nbsd_nat_target::thread_alive): Add.
>        (nbsd_nat_target::thread_name): Likewise.
>        (nbsd_nat_target::update_thread_list): Likewise.
>        (update_thread_list::post_attach): Likewise.
>        (post_attach::pid_to_str): Likewise.
>        * nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
>        (nbsd_thread_lister): Add.
>        (nbsd_nat_target::thread_alive): Likewise.
>        (nbsd_nat_target::thread_name): Likewise.
>        (nbsd_add_threads): Likewise.
>        (update_thread_list::post_attach): Likewise.
>        (nbsd_nat_target::update_thread_list): Likewise.
>        (post_attach::pid_to_str): Likewise.
> ---
>  gdb/ChangeLog  |  17 ++++++
>  gdb/nbsd-nat.c | 160 +++++++++++++++++++++++++++++++++++++++++++++++++
>  gdb/nbsd-nat.h |   8 +++
>  3 files changed, 185 insertions(+)
>
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index ef62216e0ad..764b65d872d 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,3 +1,20 @@
> +2020-04-01  Kamil Rytarowski  <n54@gmx.com>
> +
> +	* nbsd-nat.h (struct thread_info): Add forward declaration.
> +	(nbsd_nat_target::thread_alive): Add.
> +	(nbsd_nat_target::thread_name): Likewise.
> +	(nbsd_nat_target::update_thread_list): Likewise.
> +	(update_thread_list::post_attach): Likewise.
> +	(post_attach::pid_to_str): Likewise.
> +	* nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
> +	(nbsd_thread_lister): Add.
> +	(nbsd_nat_target::thread_alive): Likewise.
> +	(nbsd_nat_target::thread_name): Likewise.
> +	(nbsd_add_threads): Likewise.
> +	(update_thread_list::post_attach): Likewise.
> +	(nbsd_nat_target::update_thread_list): Likewise.
> +	(post_attach::pid_to_str): Likewise.
> +
>  2020-04-01  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>
>
>  	* infrun.c (stop_all_threads): Update assertion, plus when
> diff --git a/gdb/nbsd-nat.c b/gdb/nbsd-nat.c
> index 326bbe3aec3..4423e19428d 100644
> --- a/gdb/nbsd-nat.c
> +++ b/gdb/nbsd-nat.c
> @@ -20,6 +20,8 @@
>  #include "defs.h"
>
>  #include "nbsd-nat.h"
> +#include "gdbthread.h"
> +#include "inferior.h"
>
>  #include <sys/types.h>
>  #include <sys/ptrace.h>
> @@ -39,3 +41,161 @@ nbsd_nat_target::pid_to_exec_file (int pid)
>      return NULL;
>    return buf;
>  }
> +
> +/* Generic thread (LWP) lister within a specified process.  The callback
> +   parameters is a C++ function that is called for each detected thread.  */
> +
> +static bool
> +nbsd_thread_lister (const pid_t pid,
> +		    gdb::function_view<bool (const struct kinfo_lwp *)>
> +		    callback)
> +{
> +  int mib[5] = {CTL_KERN, KERN_LWP, pid, sizeof (struct kinfo_lwp), 0};
> +  size_t size;
> +
> +  if (sysctl (mib, ARRAY_SIZE (mib), NULL, &size, NULL, 0) == -1 || size == 0)
> +    perror_with_name (("sysctl"));
> +
> +  mib[4] = size / sizeof (size_t);
> +
> +  gdb::unique_xmalloc_ptr<struct kinfo_lwp[]> kl
> +    ((struct kinfo_lwp *) xcalloc (size, 1));
> +
> +  if (sysctl (mib, ARRAY_SIZE (mib), kl.get (), &size, NULL, 0) == -1
> +      || size == 0)
> +    perror_with_name (("sysctl"));
> +
> +  for (size_t i = 0; i < size / sizeof (struct kinfo_lwp); i++)
> +    {
> +      struct kinfo_lwp *l = &kl[i];
> +
> +      /* Return true if the specified thread is alive.  */
> +      auto lwp_alive
> +	= [] (struct kinfo_lwp *lwp)
> +	  {
> +	    switch (lwp->l_stat)
> +	      {
> +	      case LSSLEEP:
> +	      case LSRUN:
> +	      case LSONPROC:
> +	      case LSSTOP:
> +	      case LSSUSPENDED:
> +		return true;
> +	      default:
> +		return false;
> +	      }
> +	  };
> +
> +      /* Ignore embryonic or demised threads.  */
> +      if (!lwp_alive (l))
> +	continue;
> +
> +      if (callback (l))
> +	return true;
> +    }
> +
> +  return false;
> +}
> +
> +/* Return true if PTID is still active in the inferior.  */
> +
> +bool
> +nbsd_nat_target::thread_alive (ptid_t ptid)
> +{
> +  pid_t pid = ptid.pid ();
> +  int lwp = ptid.lwp ();
> +
> +  auto fn
> +    = [&lwp] (const struct kinfo_lwp *kl)
> +      {
> +        return kl->l_lid == lwp;
> +      };
> +
> +  return nbsd_thread_lister (pid, fn);
> +}
> +
> +/* Return the name assigned to a thread by an application.  Returns
> +   the string in a static buffer.  */
> +
> +const char *
> +nbsd_nat_target::thread_name (struct thread_info *thr)
> +{
> +  ptid_t ptid = thr->ptid;
> +  pid_t pid = ptid.pid ();
> +  int lwp = ptid.lwp ();
> +
> +  static char buf[KI_LNAMELEN] = {};
> +
> +  auto fn
> +    = [&lwp] (const struct kinfo_lwp *kl)
> +      {
> +	if (kl->l_lid == lwp)
> +	  {
> +	    xsnprintf (buf, sizeof buf, "%s", kl->l_name);
> +	    return true;
> +	  }
> +	return false;
> +      };
> +
> +  if (nbsd_thread_lister (pid, fn))
> +    return buf;
> +  else
> +    return NULL;
> +}
> +
> +/* Implement the "post_attach" target_ops method.  */
> +
> +static void
> +nbsd_add_threads (nbsd_nat_target *target, pid_t pid)
> +{
> +  auto fn
> +    = [&target, &pid] (const struct kinfo_lwp *kl)
> +      {
> +	ptid_t ptid = ptid_t (pid, kl->l_lid, 0);
> +	if (!in_thread_list (target, ptid))
> +	  {
> +	    if (inferior_ptid.lwp () == 0)
> +	      thread_change_ptid (target, inferior_ptid, ptid);
> +	    else
> +	      add_thread (target, ptid);
> +	  }
> +	return false;
> +      };
> +
> +  nbsd_thread_lister (pid, fn);
> +}
> +
> +/* Implement the "post_attach" target_ops method.  */
> +
> +void
> +nbsd_nat_target::post_attach (int pid)
> +{
> +  nbsd_add_threads (this, pid);
> +}
> +
> +/* Implement the "update_thread_list" target_ops method.  */
> +
> +void
> +nbsd_nat_target::update_thread_list ()
> +{
> +  prune_threads ();
> +
> +  nbsd_add_threads (this, inferior_ptid.pid ());
> +}
> +
> +/* Convert PTID to a string.  */
> +
> +std::string
> +nbsd_nat_target::pid_to_str (ptid_t ptid)
> +{
> +  int lwp = ptid.lwp ();
> +
> +  if (lwp != 0)
> +    {
> +      pid_t pid = ptid.pid ();
> +
> +      return string_printf ("LWP %d of process %d", lwp, pid);
> +    }
> +
> +  return normal_pid_to_str (ptid);
> +}
> diff --git a/gdb/nbsd-nat.h b/gdb/nbsd-nat.h
> index a752fbe572d..3606048cd07 100644
> --- a/gdb/nbsd-nat.h
> +++ b/gdb/nbsd-nat.h
> @@ -22,11 +22,19 @@
>
>  #include "inf-ptrace.h"
>
> +struct thread_info;
> +
>  /* A prototype NetBSD target.  */
>
>  struct nbsd_nat_target : public inf_ptrace_target
>  {
>    char *pid_to_exec_file (int pid) override;
> +
> +  bool thread_alive (ptid_t ptid) override;
> +  const char *thread_name (struct thread_info *thr) override;
> +  void post_attach (int pid) override;
> +  void update_thread_list () override;
> +  std::string pid_to_str (ptid_t ptid) override;
>  };
>
>  #endif /* nbsd-nat.h */
> --
> 2.25.0
>

Re: [PATCH v5] Implement basic threading support in the NetBSD target

[Tom Tromey]

>>>>> "Kamil" == Kamil Rytarowski <n54@gmx.com> writes:

Kamil> gdb/ChangeLog:

Kamil>        * nbsd-nat.h (struct thread_info): Add forward declaration.
Kamil>        (nbsd_nat_target::thread_alive): Add.
Kamil>        (nbsd_nat_target::thread_name): Likewise.
Kamil>        (nbsd_nat_target::update_thread_list): Likewise.
Kamil>        (update_thread_list::post_attach): Likewise.
Kamil>        (post_attach::pid_to_str): Likewise.
Kamil>        * nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
Kamil>        (nbsd_thread_lister): Add.
Kamil>        (nbsd_nat_target::thread_alive): Likewise.
Kamil>        (nbsd_nat_target::thread_name): Likewise.
Kamil>        (nbsd_add_threads): Likewise.
Kamil>        (update_thread_list::post_attach): Likewise.
Kamil>        (nbsd_nat_target::update_thread_list): Likewise.
Kamil>        (post_attach::pid_to_str): Likewise.

Thanks, this is ok.

vTom

Re: [PATCH] Implement basic threading support in the NetBSD target

[Tom Tromey]

>>>>> "Kamil" == Kamil Rytarowski <n54@gmx.com> writes:

Kamil> Use sysctl(3) as the portable interface to prompt NetBSD threads on
Kamil> all supported NetBSD versions. In future newer versions could switch
Kamil> to PT_LWPSTATUS ptrace(2) API that will be supported on NetBSD 10.0
Kamil> and newer.

Thank you for the patch.

Kamil> +static void
Kamil> +nbsd_thread_lister (const pid_t pid,
Kamil> +		    std::function<bool (const struct kinfo_lwp *)> callback)

Perhaps a const reference here would be better.
Or maybe gdb::function_view, I'm not sure.

Kamil> +      /* Return true if the specified thread is alive.  */
Kamil> +      auto lwp_alive =
Kamil> +	[&l]()
Kamil> +	{
Kamil> +	  switch (kl->l_stat)
Kamil> +	    {
Kamil> +	    case LSSLEEP:
Kamil> +	    case LSRUN:
Kamil> +	    case LSONPROC:
Kamil> +	    case LSSTOP:
Kamil> +	    case LSSUSPENDED:
Kamil> +	      return true;
Kamil> +	    default:
Kamil> +	      return false;
Kamil> +	    }
Kamil> +	};
Kamil> +
Kamil> +      /* Ignore embryonic or demised threads.  */
Kamil> +      if (!lwp_alive (l))
Kamil> +	continue;

I don't think a lambda is needed here.

Kamil> +bool
Kamil> +nbsd_nat_target::thread_alive (ptid_t ptid)
Kamil> +{
Kamil> +  pid_t pid = ptid.pid ();
Kamil> +  int lwp = ptid.lwp ();
Kamil> +  bool found = false;
Kamil> +
Kamil> +  auto fn =
Kamil> +    [&lwp, &found] (const struct kinfo_lwp *kl)
Kamil> +    {
Kamil> +      if (kl->l_lid == lwp)
Kamil> +	{
Kamil> +	  found = true;
Kamil> +	  return true;
Kamil> +	}
Kamil> +      return false;
Kamil> +    };
Kamil> +
Kamil> +  nbsd_thread_lister (pid, fn);
Kamil> +
Kamil> +  return found;

A classic pattern in gdb is to have one of these iteration functions
(here, nbsd_thread_lister) return bool and have it return true if any
callback returns true, and false otherwise.

That would eliminate this "found" variable.

Kamil> +const char *
Kamil> +nbsd_nat_target::thread_name (struct thread_info *thr)
Kamil> +{
Kamil> +  static char buf[KI_LNAMELEN] = {};
...
Kamil> +  return buf;

This should return NULL if no name was found.
The above bool return would make this easy as well.

Kamil> +      fprintf_unfiltered (gdb_stdlog, "NLWP: pid=%d lwp=%d\n", pid, kl->l_lid);

This line should be removed.

Tom

Re: [PATCH] Implement basic threading support in the NetBSD target

[Kamil Rytarowski]

On 01.04.2020 22:43, Tom Tromey wrote:
>>>>>> "Kamil" == Kamil Rytarowski <n54@gmx.com> writes:
>
> Kamil> Use sysctl(3) as the portable interface to prompt NetBSD threads on
> Kamil> all supported NetBSD versions. In future newer versions could switch
> Kamil> to PT_LWPSTATUS ptrace(2) API that will be supported on NetBSD 10.0
> Kamil> and newer.
>
> Thank you for the patch.
>
> Kamil> +static void
> Kamil> +nbsd_thread_lister (const pid_t pid,
> Kamil> +		    std::function<bool (const struct kinfo_lwp *)> callback)
>
> Perhaps a const reference here would be better.
> Or maybe gdb::function_view, I'm not sure.
>

I've switched to gdb::function_view.

> Kamil> +      /* Return true if the specified thread is alive.  */
> Kamil> +      auto lwp_alive =
> Kamil> +	[&l]()
> Kamil> +	{
> Kamil> +	  switch (kl->l_stat)
> Kamil> +	    {
> Kamil> +	    case LSSLEEP:
> Kamil> +	    case LSRUN:
> Kamil> +	    case LSONPROC:
> Kamil> +	    case LSSTOP:
> Kamil> +	    case LSSUSPENDED:
> Kamil> +	      return true;
> Kamil> +	    default:
> Kamil> +	      return false;
> Kamil> +	    }
> Kamil> +	};
> Kamil> +
> Kamil> +      /* Ignore embryonic or demised threads.  */
> Kamil> +      if (!lwp_alive (l))
> Kamil> +	continue;
>
> I don't think a lambda is needed here.
>

I like lambda here as it matches the internals of the kernel behavior
here. Normally, I would add a local lwp_alive() helper function, but as
it is not needed anywhere else, I added it as a local inline lambda
function.

Using lambda a little bit simplifies the code as I can avoid "break"
that is nested inside for() and switch(). I could rewrite the code, but
in the current form it nicer reflects the NetBSD kernel.

PT_LWPSTATUS/PT_LWPNEXT would have implied lwp_alive().

> Kamil> +bool
> Kamil> +nbsd_nat_target::thread_alive (ptid_t ptid)
> Kamil> +{
> Kamil> +  pid_t pid = ptid.pid ();
> Kamil> +  int lwp = ptid.lwp ();
> Kamil> +  bool found = false;
> Kamil> +
> Kamil> +  auto fn =
> Kamil> +    [&lwp, &found] (const struct kinfo_lwp *kl)
> Kamil> +    {
> Kamil> +      if (kl->l_lid == lwp)
> Kamil> +	{
> Kamil> +	  found = true;
> Kamil> +	  return true;
> Kamil> +	}
> Kamil> +      return false;
> Kamil> +    };
> Kamil> +
> Kamil> +  nbsd_thread_lister (pid, fn);
> Kamil> +
> Kamil> +  return found;
>
> A classic pattern in gdb is to have one of these iteration functions
> (here, nbsd_thread_lister) return bool and have it return true if any
> callback returns true, and false otherwise.
>
> That would eliminate this "found" variable.
>

Done.

> Kamil> +const char *
> Kamil> +nbsd_nat_target::thread_name (struct thread_info *thr)
> Kamil> +{
> Kamil> +  static char buf[KI_LNAMELEN] = {};
> ...
> Kamil> +  return buf;
>
> This should return NULL if no name was found.
> The above bool return would make this easy as well.
>

Done.

> Kamil> +      fprintf_unfiltered (gdb_stdlog, "NLWP: pid=%d lwp=%d\n", pid, kl->l_lid);
>
> This line should be removed.
>

It was fixed in v2.

> Tom
>

Please review:

[PATCH v4] Implement basic threading support in the NetBSD target