[PATCH -tip 0/3] tracepoint: Add signal events

[PATCH -tip 0/3] tracepoint: Add signal events

[Masami Hiramatsu]

Hi,

These patches add signal related tracepoints including
signal generation, delivery, and loss. First patch also
moves signal-sending tracepoint from events/sched.h to
events/signal.h.

TODO:
- Add signal-wakeup event?

Thank you,

---

Masami Hiramatsu (3):
      tracepoint: Add signal loss events
      tracepoint: Add signal deliver event
      tracepoint: Move signal sending tracepoint to events/signal.h


 include/trace/events/sched.h  |   25 --------
 include/trace/events/signal.h |  133 +++++++++++++++++++++++++++++++++++++++++
 kernel/signal.c               |   27 ++++++--
 3 files changed, 153 insertions(+), 32 deletions(-)
 create mode 100644 include/trace/events/signal.h

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division
e-mail: mhiramat@redhat.com

[PATCH -tip 1/3] tracepoint: Move signal sending tracepoint to events/signal.h

[Masami Hiramatsu]

Move signal sending event to events/signal.h. This patch also renames
sched_signal_send event to signal_generate.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
---

 include/trace/events/sched.h  |   25 -------------------------
 include/trace/events/signal.h |   38 ++++++++++++++++++++++++++++++++++++++
 kernel/signal.c               |    5 +++--
 3 files changed, 41 insertions(+), 27 deletions(-)
 create mode 100644 include/trace/events/signal.h

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index b50b985..b221bb3 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -320,31 +320,6 @@ TRACE_EVENT(sched_process_fork,
 );
 
 /*
- * Tracepoint for sending a signal:
- */
-TRACE_EVENT(sched_signal_send,
-
-	TP_PROTO(int sig, struct task_struct *p),
-
-	TP_ARGS(sig, p),
-
-	TP_STRUCT__entry(
-		__field(	int,	sig			)
-		__array(	char,	comm,	TASK_COMM_LEN	)
-		__field(	pid_t,	pid			)
-	),
-
-	TP_fast_assign(
-		memcpy(__entry->comm, p->comm, TASK_COMM_LEN);
-		__entry->pid	= p->pid;
-		__entry->sig	= sig;
-	),
-
-	TP_printk("sig=%d comm=%s pid=%d",
-		  __entry->sig, __entry->comm, __entry->pid)
-);
-
-/*
  * XXX the below sched_stat tracepoints only apply to SCHED_OTHER/BATCH/IDLE
  *     adding sched_stat support to SCHED_FIFO/RR would be welcome.
  */
diff --git a/include/trace/events/signal.h b/include/trace/events/signal.h
new file mode 100644
index 0000000..c7817f3
--- /dev/null
+++ b/include/trace/events/signal.h
@@ -0,0 +1,38 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM signal
+
+#if !defined(_TRACE_SIGNAL_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_SIGNAL_H
+
+#include <linux/sched.h>
+#include <linux/tracepoint.h>
+
+/*
+ * Tracepoint for generating a signal:
+ */
+TRACE_EVENT(signal_generate,
+
+	TP_PROTO(int sig, struct task_struct *p),
+
+	TP_ARGS(sig, p),
+
+	TP_STRUCT__entry(
+		__field(	int,	sig			)
+		__array(	char,	comm,	TASK_COMM_LEN	)
+		__field(	pid_t,	pid			)
+	),
+
+	TP_fast_assign(
+		memcpy(__entry->comm, p->comm, TASK_COMM_LEN);
+		__entry->pid	= p->pid;
+		__entry->sig	= sig;
+	),
+
+	TP_printk("sig=%d comm=%s pid=%d",
+		  __entry->sig, __entry->comm, __entry->pid)
+);
+
+#endif /* _TRACE_SIGNAL_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/kernel/signal.c b/kernel/signal.c
index fe08008..82ab077 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -28,7 +28,8 @@
 #include <linux/freezer.h>
 #include <linux/pid_namespace.h>
 #include <linux/nsproxy.h>
-#include <trace/events/sched.h>
+#define CREATE_TRACE_POINTS
+#include <trace/events/signal.h>
 
 #include <asm/param.h>
 #include <asm/uaccess.h>
@@ -856,7 +857,7 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
 	struct sigqueue *q;
 	int override_rlimit;
 
-	trace_sched_signal_send(sig, t);
+	trace_signal_generate(sig, t);
 
 	assert_spin_locked(&t->sighand->siglock);
 


-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com

[PATCH -tip 2/3] tracepoint: Add signal deliver event

[Masami Hiramatsu]

Add a tracepoint where a process gets a signal. This tracepoint
shows signal-number, sa-handler and sa-flag.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
---

 include/trace/events/signal.h |   24 ++++++++++++++++++++++++
 kernel/signal.c               |    3 +++
 2 files changed, 27 insertions(+), 0 deletions(-)

diff --git a/include/trace/events/signal.h b/include/trace/events/signal.h
index c7817f3..6dfd88d 100644
--- a/include/trace/events/signal.h
+++ b/include/trace/events/signal.h
@@ -32,6 +32,30 @@ TRACE_EVENT(signal_generate,
 		  __entry->sig, __entry->comm, __entry->pid)
 );
 
+/*
+ * Tracepoint for delivering a signal:
+ */
+TRACE_EVENT(signal_deliver,
+
+	TP_PROTO(int sig, struct k_sigaction *ka),
+
+	TP_ARGS(sig, ka),
+
+	TP_STRUCT__entry(
+		__field(	int,		sig		)
+		__field(	unsigned long,	sa_handler	)
+		__field(	unsigned long,	sa_flags	)
+	),
+
+	TP_fast_assign(
+		__entry->sig	= sig;
+		__entry->sa_handler	= (unsigned long)ka->sa.sa_handler;
+		__entry->sa_flags	= ka->sa.sa_flags;
+	),
+
+	TP_printk("sig=%d sa_handler=%lx sa_flags=%lx",
+		  __entry->sig, __entry->sa_handler, __entry->sa_flags)
+);
 #endif /* _TRACE_SIGNAL_H */
 
 /* This part must be outside protection */
diff --git a/kernel/signal.c b/kernel/signal.c
index 82ab077..5615f41 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1860,6 +1860,9 @@ relock:
 			ka = &sighand->action[signr-1];
 		}
 
+		/* Trace the actual delivered signals including SIG_IGN.*/
+		trace_signal_deliver(signr, ka);
+
 		if (ka->sa.sa_handler == SIG_IGN) /* Do nothing.  */
 			continue;
 		if (ka->sa.sa_handler != SIG_DFL) {


-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com

[PATCH -tip 3/3] tracepoint: Add signal loss events

[Masami Hiramatsu]

Add signal_overflow_fail and signal_lose_info tracepoints
for signal-lost events.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Suggested-by: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
---

 include/trace/events/signal.h |   71 +++++++++++++++++++++++++++++++++++++++++
 kernel/signal.c               |   19 ++++++++---
 2 files changed, 85 insertions(+), 5 deletions(-)

diff --git a/include/trace/events/signal.h b/include/trace/events/signal.h
index 6dfd88d..eb57285 100644
--- a/include/trace/events/signal.h
+++ b/include/trace/events/signal.h
@@ -4,6 +4,7 @@
 #if !defined(_TRACE_SIGNAL_H) || defined(TRACE_HEADER_MULTI_READ)
 #define _TRACE_SIGNAL_H
 
+#include <linux/signal.h>
 #include <linux/sched.h>
 #include <linux/tracepoint.h>
 
@@ -56,6 +57,76 @@ TRACE_EVENT(signal_deliver,
 	TP_printk("sig=%d sa_handler=%lx sa_flags=%lx",
 		  __entry->sig, __entry->sa_handler, __entry->sa_flags)
 );
+
+/*
+ * Tracepoint for losing a signal by overflow:
+ */
+TRACE_EVENT(signal_overflow_fail,
+
+	TP_PROTO(int sig, int group, struct siginfo *info),
+
+	TP_ARGS(sig, group, info),
+
+	TP_STRUCT__entry(
+		__field(	int,	sig	)
+		__field(	int,	group	)
+		__field(	int,	errno	)
+		__field(	int,	code	)
+	),
+
+	TP_fast_assign(
+		__entry->sig	= sig;
+		__entry->group	= group;
+		if (info == SEND_SIG_NOINFO) {
+			__entry->errno	= 0;
+			__entry->code	= SI_USER;
+		} else if (info == SEND_SIG_PRIV) {
+			__entry->errno	= 0;
+			__entry->code	= SI_KERNEL;
+		} else {
+			__entry->errno	= info->si_errno;
+			__entry->code	= info->si_code;
+		}
+	),
+
+	TP_printk("sig=%d group=%d errno=%d code=%d",
+		  __entry->sig, __entry->group, __entry->errno, __entry->code)
+);
+
+/*
+ * Tracepoint for losing a siginfo:
+ */
+TRACE_EVENT(signal_lose_info,
+
+	TP_PROTO(int sig, int group, struct siginfo *info),
+
+	TP_ARGS(sig, group, info),
+
+	TP_STRUCT__entry(
+		__field(	int,	sig	)
+		__field(	int,	group	)
+		__field(	int,	errno	)
+		__field(	int,	code	)
+	),
+
+	TP_fast_assign(
+		__entry->sig	= sig;
+		__entry->group	= group;
+		if (info == SEND_SIG_NOINFO) {
+			__entry->errno	= 0;
+			__entry->code	= SI_USER;
+		} else if (info == SEND_SIG_PRIV) {
+			__entry->errno	= 0;
+			__entry->code	= SI_KERNEL;
+		} else {
+			__entry->errno	= info->si_errno;
+			__entry->code	= info->si_code;
+		}
+	),
+
+	TP_printk("sig=%d group=%d errno=%d code=%d",
+		  __entry->sig, __entry->group, __entry->errno, __entry->code)
+);
 #endif /* _TRACE_SIGNAL_H */
 
 /* This part must be outside protection */
diff --git a/kernel/signal.c b/kernel/signal.c
index 5615f41..65f67c5 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -919,12 +919,21 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
 			break;
 		}
 	} else if (!is_si_special(info)) {
-		if (sig >= SIGRTMIN && info->si_code != SI_USER)
-		/*
-		 * Queue overflow, abort.  We may abort if the signal was rt
-		 * and sent by user using something other than kill().
-		 */
+		if (sig >= SIGRTMIN && info->si_code != SI_USER) {
+			/*
+			 * Queue overflow, abort.  We may abort if the
+			 * signal was rt and sent by user using something
+			 * other than kill().
+			 */
+			trace_signal_overflow_fail(sig, group, info);
 			return -EAGAIN;
+		} else {
+			/*
+			 * This is a silent loss of information.  We still
+			 * send the signal, but the *info bits are lost.
+			 */
+			trace_signal_lose_info(sig, group, info);
+		}
 	}
 
 out_set:


-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com

Re: [PATCH -tip 0/3] tracepoint: Add signal events

[Roland McGrath]

I would add the siginfo_t * argument to each of these tracepoints.

In 2/3 this comment:

+		/* Trace the actual delivered signals including SIG_IGN.*/

might be slightly misleading.  In most cases SIG_IGN signals won't make it
this far.  The same is true of SIG_DFL signals whose default action is to
ignore.  So one should be clear that trace_signal_deliver() is by no means
expected to get all SIG_IGN signals that are otherwise eligible for delivery.


Thanks,
Roland

Re: [PATCH -tip 0/3] tracepoint: Add signal events

[Masami Hiramatsu]

Roland McGrath wrote:
> I would add the siginfo_t * argument to each of these tracepoints.

I see. Is it OK to record only si_errno and si_code? because si_signo
might be as same as sig.

> In 2/3 this comment:
>
> +		/* Trace the actual delivered signals including SIG_IGN.*/
>
> might be slightly misleading.  In most cases SIG_IGN signals won't make it
> this far.  The same is true of SIG_DFL signals whose default action is to
> ignore.  So one should be clear that trace_signal_deliver() is by no means
> expected to get all SIG_IGN signals that are otherwise eligible for delivery.

Ah, thank you for noticing. I'll remove the last words.

Thank you,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com

Re: [PATCH -tip 0/3] tracepoint: Add signal events

[Roland McGrath]

> Roland McGrath wrote:
> > I would add the siginfo_t * argument to each of these tracepoints.
> 
> I see. Is it OK to record only si_errno and si_code? because si_signo
> might be as same as sig.

Yes, si_signo will match sig.  Which siginfo_t fields are interesting to
record can vary by signal (i.e. by si_code).  si_code and si_errno are
certainly the first things that come to mind as most useful.  For SI_TIMER,
si_tid, si_overrun, and si_sigval are interesting.  For others, si_pid and
si_uid are interesting.


Thanks,
Roland