[review] Turn off threaded minsym demangling by default

[review] Turn off threaded minsym demangling by default

[Christian Biesinger (Code Review)]

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/687
......................................................................

Turn off threaded minsym demangling by default

Per discussion on gdb-patches with Joel, this patch turns off multihreaded
symbol loading by default. It can be turned on using:
  maint set worker-threads unlimited

To keep the behavior as close as possible to the old code, it still
calls symbol_set_names in the old place if n_worker_threads is 0.

gdb/ChangeLog:

2019-11-18  Christian Biesinger  <cbiesinger@google.com>

	* maint.c (n_worker_threads): Default to 0.
	(worker_threads_disabled): New function.
	* maint.h (worker_threads_disabled): New function.
	* minsyms.c (minimal_symbol_reader::record_full): Call symbol_set_names
	here if worker_threads_disabled () is true.
	(minimal_symbol_reader::install): Skip all threading if
	worker_threads_disabled () is true.

Change-Id: I92ba4f6bbf07363189666327cad452d6b9c8e01d
---
M gdb/maint.c
M gdb/maint.h
M gdb/minsyms.c
3 files changed, 47 insertions(+), 30 deletions(-)



diff --git a/gdb/maint.c b/gdb/maint.c
index fce1a1c..3e14c3e 100644
--- a/gdb/maint.c
+++ b/gdb/maint.c
@@ -845,7 +845,12 @@
 }
 #endif
 
-static int n_worker_threads = -1;
+static int n_worker_threads = 0;
+
+bool worker_threads_disabled ()
+{
+  return n_worker_threads == 0;
+}
 
 /* Update the thread pool for the desired number of threads.  */
 static void
diff --git a/gdb/maint.h b/gdb/maint.h
index 827964d..cbaf9de 100644
--- a/gdb/maint.h
+++ b/gdb/maint.h
@@ -26,6 +26,8 @@
 
 extern void set_per_command_space (int);
 
+extern bool worker_threads_disabled ();
+
 /* Records a run time and space usage to be used as a base for
    reporting elapsed time or change in space.  */
 
diff --git a/gdb/minsyms.c b/gdb/minsyms.c
index f9d1172..b59b96d 100644
--- a/gdb/minsyms.c
+++ b/gdb/minsyms.c
@@ -53,6 +53,7 @@
 #include "gdbsupport/symbol.h"
 #include <algorithm>
 #include "safe-ctype.h"
+#include "maint.h"
 #include "gdbsupport/parallel-for.h"
 
 #if CXX_STD_THREAD
@@ -1139,6 +1140,12 @@
   else
     msymbol->name = name.data ();
 
+  if (worker_threads_disabled ())
+    /* To keep our behavior as close as possible to the previous non-threaded
+       behavior for GDB 9.1, we call symbol_set_names here when threads
+       are disabled.  */
+    symbol_set_names (msymbol, msymbol->name, false, m_objfile->per_bfd);
+
   SET_MSYMBOL_VALUE_ADDRESS (msymbol, address);
   MSYMBOL_SECTION (msymbol) = section;
 
@@ -1364,43 +1371,46 @@
       m_objfile->per_bfd->minimal_symbol_count = mcount;
       m_objfile->per_bfd->msymbols = std::move (msym_holder);
 
+      if (!worker_threads_disabled ())
+	{
 #if CXX_STD_THREAD
-      /* Mutex that is used when modifying or accessing the demangled
-	 hash table.  */
-      std::mutex demangled_mutex;
+	  /* Mutex that is used when modifying or accessing the demangled
+	     hash table.  */
+	  std::mutex demangled_mutex;
 #endif
 
-      msymbols = m_objfile->per_bfd->msymbols.get ();
-      gdb::parallel_for_each
-	(&msymbols[0], &msymbols[mcount],
-	 [&] (minimal_symbol *start, minimal_symbol *end)
-	 {
-	   for (minimal_symbol *msym = start; msym < end; ++msym)
+	  msymbols = m_objfile->per_bfd->msymbols.get ();
+	  gdb::parallel_for_each
+	    (&msymbols[0], &msymbols[mcount],
+	     [&] (minimal_symbol *start, minimal_symbol *end)
 	     {
-	       if (!msym->name_set)
+	       for (minimal_symbol *msym = start; msym < end; ++msym)
 		 {
-		   /* This will be freed later, by symbol_set_names.  */
-		   char *demangled_name
-		     = symbol_find_demangled_name (msym, msym->name);
-		   symbol_set_demangled_name
-		     (msym, demangled_name,
-		      &m_objfile->per_bfd->storage_obstack);
-		   msym->name_set = 1;
+		   if (!msym->name_set)
+		     {
+		       /* This will be freed later, by symbol_set_names.  */
+		       char *demangled_name
+			 = symbol_find_demangled_name (msym, msym->name);
+		       symbol_set_demangled_name
+			 (msym, demangled_name,
+			  &m_objfile->per_bfd->storage_obstack);
+		       msym->name_set = 1;
+		     }
 		 }
-	     }
-	   {
-	     /* To limit how long we hold the lock, we only acquire it here
-	        and not while we demangle the names above.  */
-#if CXX_STD_THREAD
-	     std::lock_guard<std::mutex> guard (demangled_mutex);
-#endif
-	     for (minimal_symbol *msym = start; msym < end; ++msym)
 	       {
-		 symbol_set_names (msym, msym->name, false,
-				   m_objfile->per_bfd);
+		 /* To limit how long we hold the lock, we only acquire it here
+		    and not while we demangle the names above.  */
+#if CXX_STD_THREAD
+		 std::lock_guard<std::mutex> guard (demangled_mutex);
+#endif
+		 for (minimal_symbol *msym = start; msym < end; ++msym)
+		   {
+		     symbol_set_names (msym, msym->name, false,
+				       m_objfile->per_bfd);
+		   }
 	       }
-	   }
-	 });
+	     });
+	}
 
       build_minimal_symbol_hash_tables (m_objfile);
     }

-- 
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: I92ba4f6bbf07363189666327cad452d6b9c8e01d
Gerrit-Change-Number: 687
Gerrit-PatchSet: 1
Gerrit-Owner: Christian Biesinger <cbiesinger@google.com>
Gerrit-MessageType: newchange

[review] Turn off threaded minsym demangling by default

[Christian Biesinger (Code Review)]

Christian Biesinger has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/687
......................................................................


Patch Set 1:

tromey -- sorry I missed your IRC question; here I did more than just change the setting because I was concerned that deferring the symbol_set_names call may have a risk in case some code relies on the name being set earlier. Beyond that I skipped all the threading set up because it's not necessary with that first part. But if you think I'm overly cautious I'm fine with not doing that.


-- 
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: I92ba4f6bbf07363189666327cad452d6b9c8e01d
Gerrit-Change-Number: 687
Gerrit-PatchSet: 1
Gerrit-Owner: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Christian Biesinger <cbiesinger@google.com>
Gerrit-Comment-Date: Tue, 19 Nov 2019 21:54:01 +0000
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Gerrit-MessageType: comment

[review] Turn off threaded minsym demangling by default

[Tom Tromey (Code Review)]

Tom Tromey has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/687
......................................................................


Patch Set 1: Code-Review+2

I finally got around to reading this.

I think this makes sense.  And, I think it's fine to revert immediately
after the 9.1 branch is created.

Thanks for doing this.


-- 
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: I92ba4f6bbf07363189666327cad452d6b9c8e01d
Gerrit-Change-Number: 687
Gerrit-PatchSet: 1
Gerrit-Owner: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Tom Tromey <tromey@sourceware.org>
Gerrit-Comment-Date: Fri, 22 Nov 2019 23:48:25 +0000
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[review v2] Turn off threaded minsym demangling by default

[Christian Biesinger (Code Review)]

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/687
......................................................................

Turn off threaded minsym demangling by default

Per discussion on gdb-patches with Joel, this patch turns off multihreaded
symbol loading by default. It can be turned on using:
  maint set worker-threads unlimited

To keep the behavior as close as possible to the old code, it still
calls symbol_set_names in the old place if n_worker_threads is 0.

gdb/ChangeLog:

2019-11-18  Christian Biesinger  <cbiesinger@google.com>

	* maint.c (n_worker_threads): Default to 0.
	(worker_threads_disabled): New function.
	* maint.h (worker_threads_disabled): New function.
	* minsyms.c (minimal_symbol_reader::record_full): Call symbol_set_names
	here if worker_threads_disabled () is true.
	(minimal_symbol_reader::install): Skip all threading if
	worker_threads_disabled () is true.

Change-Id: I92ba4f6bbf07363189666327cad452d6b9c8e01d
---
M gdb/maint.c
M gdb/maint.h
M gdb/minsyms.c
3 files changed, 23 insertions(+), 4 deletions(-)



diff --git a/gdb/maint.c b/gdb/maint.c
index 7ab3fdb..dbc949a 100644
--- a/gdb/maint.c
+++ b/gdb/maint.c
@@ -845,7 +845,12 @@
 }
 #endif
 
-static int n_worker_threads = -1;
+static int n_worker_threads = 0;
+
+bool worker_threads_disabled ()
+{
+  return n_worker_threads == 0;
+}
 
 /* Update the thread pool for the desired number of threads.  */
 static void
diff --git a/gdb/maint.h b/gdb/maint.h
index 827964d..cbaf9de 100644
--- a/gdb/maint.h
+++ b/gdb/maint.h
@@ -26,6 +26,8 @@
 
 extern void set_per_command_space (int);
 
+extern bool worker_threads_disabled ();
+
 /* Records a run time and space usage to be used as a base for
    reporting elapsed time or change in space.  */
 
diff --git a/gdb/minsyms.c b/gdb/minsyms.c
index b752b3a..de8cb78 100644
--- a/gdb/minsyms.c
+++ b/gdb/minsyms.c
@@ -54,6 +54,7 @@
 #include <algorithm>
 #include "safe-ctype.h"
 #include "gdbsupport/parallel-for.h"
+#include "maint.h"
 
 #if CXX_STD_THREAD
 #include <mutex>
@@ -1137,6 +1138,15 @@
   else
     msymbol->name = name.data ();
 
+  if (worker_threads_disabled ())
+    {
+      /* To keep our behavior as close as possible to the previous non-threaded
+	 behavior for GDB 9.1, we call symbol_set_names here when threads
+	 are disabled.  */
+      symbol_set_names (msymbol, msymbol->name, false, m_objfile->per_bfd);
+      msymbol->name_set = 1;
+    }
+
   SET_MSYMBOL_VALUE_ADDRESS (msymbol, address);
   MSYMBOL_SECTION (msymbol) = section;
 
@@ -1401,10 +1411,12 @@
 		     (msym, demangled_name,
 		      &m_objfile->per_bfd->storage_obstack);
 		   msym->name_set = 1;
-
-		   hash_values[idx].mangled_name_hash
-		     = fast_hash (msym->name, hash_values[idx].name_length);
 		 }
+	       /* This mangled_name_hash computation has to be outside of
+		  the name_set check, or symbol_set_names below will
+		  be called with an invalid hash value.  */
+	       hash_values[idx].mangled_name_hash
+		 = fast_hash (msym->name, hash_values[idx].name_length);
 	       hash_values[idx].minsym_hash
 		 = msymbol_hash (msym->linkage_name ());
 	       hash_values[idx].minsym_demangled_hash

-- 
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: I92ba4f6bbf07363189666327cad452d6b9c8e01d
Gerrit-Change-Number: 687
Gerrit-PatchSet: 2
Gerrit-Owner: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Tom Tromey <tromey@sourceware.org>
Gerrit-MessageType: newpatchset

[review v2] Turn off threaded minsym demangling by default

[Tom Tromey (Code Review)]

Tom Tromey has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/687
......................................................................


Patch Set 2: Code-Review+2

Still looks good.  Thanks for doing this.


-- 
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: I92ba4f6bbf07363189666327cad452d6b9c8e01d
Gerrit-Change-Number: 687
Gerrit-PatchSet: 2
Gerrit-Owner: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Tom Tromey <tromey@sourceware.org>
Gerrit-Comment-Date: Tue, 26 Nov 2019 21:55:53 +0000
Gerrit-HasComments: No
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Gerrit-MessageType: comment

[pushed] Turn off threaded minsym demangling by default

[Sourceware to Gerrit sync (Code Review)]

The original change was created by Christian Biesinger.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/687
......................................................................

Turn off threaded minsym demangling by default

Per discussion on gdb-patches with Joel, this patch turns off multihreaded
symbol loading by default. It can be turned on using:
  maint set worker-threads unlimited

To keep the behavior as close as possible to the old code, it still
calls symbol_set_names in the old place if n_worker_threads is 0.

gdb/ChangeLog:

2019-11-27  Christian Biesinger  <cbiesinger@google.com>

	* maint.c (n_worker_threads): Default to 0.
	(worker_threads_disabled): New function.
	* maint.h (worker_threads_disabled): New function.
	* minsyms.c (minimal_symbol_reader::record_full): Call symbol_set_names
	here if worker_threads_disabled () is true.
	(minimal_symbol_reader::install): Skip all threading if
	worker_threads_disabled () is true.

Change-Id: I92ba4f6bbf07363189666327cad452d6b9c8e01d
---
M gdb/ChangeLog
M gdb/maint.c
M gdb/maint.h
M gdb/minsyms.c
4 files changed, 33 insertions(+), 4 deletions(-)



diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 64c8ab5..3033cf6 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,15 @@
 2019-11-27  Christian Biesinger  <cbiesinger@google.com>
 
+	* maint.c (n_worker_threads): Default to 0.
+	(worker_threads_disabled): New function.
+	* maint.h (worker_threads_disabled): New function.
+	* minsyms.c (minimal_symbol_reader::record_full): Call symbol_set_names
+	here if worker_threads_disabled () is true.
+	(minimal_symbol_reader::install): Skip all threading if
+	worker_threads_disabled () is true.
+
+2019-11-27  Christian Biesinger  <cbiesinger@google.com>
+
 	* minsyms.c (add_minsym_to_hash_table): Use a previously computed
 	hash code if possible.
 	(add_minsym_to_demangled_hash_table): Likewise.
diff --git a/gdb/maint.c b/gdb/maint.c
index 7ab3fdb..dbc949a 100644
--- a/gdb/maint.c
+++ b/gdb/maint.c
@@ -845,7 +845,12 @@
 }
 #endif
 
-static int n_worker_threads = -1;
+static int n_worker_threads = 0;
+
+bool worker_threads_disabled ()
+{
+  return n_worker_threads == 0;
+}
 
 /* Update the thread pool for the desired number of threads.  */
 static void
diff --git a/gdb/maint.h b/gdb/maint.h
index 827964d..cbaf9de 100644
--- a/gdb/maint.h
+++ b/gdb/maint.h
@@ -26,6 +26,8 @@
 
 extern void set_per_command_space (int);
 
+extern bool worker_threads_disabled ();
+
 /* Records a run time and space usage to be used as a base for
    reporting elapsed time or change in space.  */
 
diff --git a/gdb/minsyms.c b/gdb/minsyms.c
index 94240c9..4f7260b 100644
--- a/gdb/minsyms.c
+++ b/gdb/minsyms.c
@@ -54,6 +54,7 @@
 #include <algorithm>
 #include "safe-ctype.h"
 #include "gdbsupport/parallel-for.h"
+#include "maint.h"
 
 #if CXX_STD_THREAD
 #include <mutex>
@@ -1137,6 +1138,15 @@
   else
     msymbol->name = name.data ();
 
+  if (worker_threads_disabled ())
+    {
+      /* To keep our behavior as close as possible to the previous non-threaded
+	 behavior for GDB 9.1, we call symbol_set_names here when threads
+	 are disabled.  */
+      symbol_set_names (msymbol, msymbol->name, false, m_objfile->per_bfd);
+      msymbol->name_set = 1;
+    }
+
   SET_MSYMBOL_VALUE_ADDRESS (msymbol, address);
   MSYMBOL_SECTION (msymbol) = section;
 
@@ -1407,10 +1417,12 @@
 		     (msym, demangled_name,
 		      &m_objfile->per_bfd->storage_obstack);
 		   msym->name_set = 1;
-
-		   hash_values[idx].mangled_name_hash
-		     = fast_hash (msym->name, hash_values[idx].name_length);
 		 }
+	       /* This mangled_name_hash computation has to be outside of
+		  the name_set check, or symbol_set_names below will
+		  be called with an invalid hash value.  */
+	       hash_values[idx].mangled_name_hash
+		 = fast_hash (msym->name, hash_values[idx].name_length);
 	       hash_values[idx].minsym_hash
 		 = msymbol_hash (msym->linkage_name ());
 	       /* We only use this hash code if the search name differs

-- 
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: I92ba4f6bbf07363189666327cad452d6b9c8e01d
Gerrit-Change-Number: 687
Gerrit-PatchSet: 3
Gerrit-Owner: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Tom Tromey <tromey@sourceware.org>
Gerrit-MessageType: newpatchset

[pushed] Turn off threaded minsym demangling by default

[Sourceware to Gerrit sync (Code Review)]

Sourceware to Gerrit sync has submitted this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/687
......................................................................

Turn off threaded minsym demangling by default

Per discussion on gdb-patches with Joel, this patch turns off multihreaded
symbol loading by default. It can be turned on using:
  maint set worker-threads unlimited

To keep the behavior as close as possible to the old code, it still
calls symbol_set_names in the old place if n_worker_threads is 0.

gdb/ChangeLog:

2019-11-27  Christian Biesinger  <cbiesinger@google.com>

	* maint.c (n_worker_threads): Default to 0.
	(worker_threads_disabled): New function.
	* maint.h (worker_threads_disabled): New function.
	* minsyms.c (minimal_symbol_reader::record_full): Call symbol_set_names
	here if worker_threads_disabled () is true.
	(minimal_symbol_reader::install): Skip all threading if
	worker_threads_disabled () is true.

Change-Id: I92ba4f6bbf07363189666327cad452d6b9c8e01d
---
M gdb/ChangeLog
M gdb/maint.c
M gdb/maint.h
M gdb/minsyms.c
4 files changed, 33 insertions(+), 4 deletions(-)


diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 64c8ab5..3033cf6 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,15 @@
 2019-11-27  Christian Biesinger  <cbiesinger@google.com>
 
+	* maint.c (n_worker_threads): Default to 0.
+	(worker_threads_disabled): New function.
+	* maint.h (worker_threads_disabled): New function.
+	* minsyms.c (minimal_symbol_reader::record_full): Call symbol_set_names
+	here if worker_threads_disabled () is true.
+	(minimal_symbol_reader::install): Skip all threading if
+	worker_threads_disabled () is true.
+
+2019-11-27  Christian Biesinger  <cbiesinger@google.com>
+
 	* minsyms.c (add_minsym_to_hash_table): Use a previously computed
 	hash code if possible.
 	(add_minsym_to_demangled_hash_table): Likewise.
diff --git a/gdb/maint.c b/gdb/maint.c
index 7ab3fdb..dbc949a 100644
--- a/gdb/maint.c
+++ b/gdb/maint.c
@@ -845,7 +845,12 @@
 }
 #endif
 
-static int n_worker_threads = -1;
+static int n_worker_threads = 0;
+
+bool worker_threads_disabled ()
+{
+  return n_worker_threads == 0;
+}
 
 /* Update the thread pool for the desired number of threads.  */
 static void
diff --git a/gdb/maint.h b/gdb/maint.h
index 827964d..cbaf9de 100644
--- a/gdb/maint.h
+++ b/gdb/maint.h
@@ -26,6 +26,8 @@
 
 extern void set_per_command_space (int);
 
+extern bool worker_threads_disabled ();
+
 /* Records a run time and space usage to be used as a base for
    reporting elapsed time or change in space.  */
 
diff --git a/gdb/minsyms.c b/gdb/minsyms.c
index 94240c9..4f7260b 100644
--- a/gdb/minsyms.c
+++ b/gdb/minsyms.c
@@ -54,6 +54,7 @@
 #include <algorithm>
 #include "safe-ctype.h"
 #include "gdbsupport/parallel-for.h"
+#include "maint.h"
 
 #if CXX_STD_THREAD
 #include <mutex>
@@ -1137,6 +1138,15 @@
   else
     msymbol->name = name.data ();
 
+  if (worker_threads_disabled ())
+    {
+      /* To keep our behavior as close as possible to the previous non-threaded
+	 behavior for GDB 9.1, we call symbol_set_names here when threads
+	 are disabled.  */
+      symbol_set_names (msymbol, msymbol->name, false, m_objfile->per_bfd);
+      msymbol->name_set = 1;
+    }
+
   SET_MSYMBOL_VALUE_ADDRESS (msymbol, address);
   MSYMBOL_SECTION (msymbol) = section;
 
@@ -1407,10 +1417,12 @@
 		     (msym, demangled_name,
 		      &m_objfile->per_bfd->storage_obstack);
 		   msym->name_set = 1;
-
-		   hash_values[idx].mangled_name_hash
-		     = fast_hash (msym->name, hash_values[idx].name_length);
 		 }
+	       /* This mangled_name_hash computation has to be outside of
+		  the name_set check, or symbol_set_names below will
+		  be called with an invalid hash value.  */
+	       hash_values[idx].mangled_name_hash
+		 = fast_hash (msym->name, hash_values[idx].name_length);
 	       hash_values[idx].minsym_hash
 		 = msymbol_hash (msym->linkage_name ());
 	       /* We only use this hash code if the search name differs

-- 
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: I92ba4f6bbf07363189666327cad452d6b9c8e01d
Gerrit-Change-Number: 687
Gerrit-PatchSet: 3
Gerrit-Owner: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Tom Tromey <tromey@sourceware.org>
Gerrit-MessageType: merged