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Backported r185231 from trunk to google/gcc-4_7. (issue 6151043)

From: asharif at chromium dot org
To: xur at google dot com, davidxl at google dot com
Cc: gcc-patches at gcc dot gnu dot org, reply at codereview-hr dot appspotmail dot com
Date: Tue, 01 May 2012 22:47:39 +0000
Subject: Backported r185231 from trunk to google/gcc-4_7. (issue 6151043)
Reply-to: asharif at chromium dot org, xur at google dot com, davidxl at google dot com, gcc-patches at gcc dot gnu dot org, reply at codereview-hr dot appspotmail dot com

Reviewers: xur, davidxl,

Message:
Please take a look at this.

Description:
This fixes an issue with profile collection when multiple threads call
fork() around the same time.

2012-03-12 Richard Guenther <rguenther@suse.de>

	* gthr.h (__GTHREAD_MUTEX_INIT_FUNCTION): Adjust specification.
	* gthr-posix.h (__GTHREAD_MUTEX_INIT_FUNCTION): Define.
	(__gthread_mutex_init_function): New function.
	* gthr-single.h (__GTHREAD_MUTEX_INIT_FUNCTION): Define.

	PR gcov/49484
	* libgcov.c: Include gthr.h.
	(__gcov_flush_mx): New global variable.
	(init_mx, init_mx_once): New functions.
	(__gcov_flush): Protect self with a mutex.
	(__gcov_fork): Re-initialize mutex after forking.
	* unwind-dw2-fde.c: Change condition under which to use
	__GTHREAD_MUTEX_INIT_FUNCTION.

Please review this at http://codereview.appspot.com/6151043/

Affected files:
   M    .
  M     libgcc/ChangeLog
  M     libgcc/ChangeLog.google-4_7
  M     libgcc/gthr-posix.h
  M     libgcc/gthr-single.h
  M     libgcc/gthr.h
  M     libgcc/libgcov.c
  M     libgcc/unwind-dw2-fde.c


Index: .
===================================================================
--- .	(revision 187027)
+++ .	(working copy)

Property changes on: .
___________________________________________________________________
Modified: svn:mergeinfo
   Merged /trunk:r185231
Index: libgcc/ChangeLog
===================================================================
--- libgcc/ChangeLog	(revision 187027)
+++ libgcc/ChangeLog	(working copy)
@@ -1,3 +1,19 @@
+2012-03-12  Richard Guenther  <rguenther@suse.de>
+
+	* gthr.h (__GTHREAD_MUTEX_INIT_FUNCTION): Adjust specification.
+	* gthr-posix.h (__GTHREAD_MUTEX_INIT_FUNCTION): Define.
+	(__gthread_mutex_init_function): New function.
+	* gthr-single.h (__GTHREAD_MUTEX_INIT_FUNCTION): Define.
+
+	PR gcov/49484
+	* libgcov.c: Include gthr.h.
+	(__gcov_flush_mx): New global variable.
+	(init_mx, init_mx_once): New functions.
+	(__gcov_flush): Protect self with a mutex.
+	(__gcov_fork): Re-initialize mutex after forking.
+	* unwind-dw2-fde.c: Change condition under which to use
+	__GTHREAD_MUTEX_INIT_FUNCTION.
+
 2012-04-20  Thomas Schwinge  <thomas@codesourcery.com>

 	struct siginfo vs. siginfo_t
Index: libgcc/ChangeLog.google-4_7
===================================================================
--- libgcc/ChangeLog.google-4_7	(revision 187027)
+++ libgcc/ChangeLog.google-4_7	(working copy)
@@ -1,3 +1,20 @@
+2012-05-01  Ahmad Sharif  <asharif@google.com>
+	2012-03-12  Richard Guenther  <rguenther@suse.de>
+
+	* gthr.h (__GTHREAD_MUTEX_INIT_FUNCTION): Adjust specification.
+	* gthr-posix.h (__GTHREAD_MUTEX_INIT_FUNCTION): Define.
+	(__gthread_mutex_init_function): New function.
+	* gthr-single.h (__GTHREAD_MUTEX_INIT_FUNCTION): Define.
+
+	PR gcov/49484
+	* libgcov.c: Include gthr.h.
+	(__gcov_flush_mx): New global variable.
+	(init_mx, init_mx_once): New functions.
+	(__gcov_flush): Protect self with a mutex.
+	(__gcov_fork): Re-initialize mutex after forking.
+	* unwind-dw2-fde.c: Change condition under which to use
+	__GTHREAD_MUTEX_INIT_FUNCTION.
+
 2012-04-17  Teresa Johnson  <tejohnson@google.com>

 	Backport from google/main rev r186550
Index: libgcc/gthr-single.h
===================================================================
--- libgcc/gthr-single.h	(revision 187027)
+++ libgcc/gthr-single.h	(working copy)
@@ -36,6 +36,7 @@

 #define __GTHREAD_ONCE_INIT 0
 #define __GTHREAD_MUTEX_INIT 0
+#define __GTHREAD_MUTEX_INIT_FUNCTION (mx)
 #define __GTHREAD_RECURSIVE_MUTEX_INIT 0

 #define UNUSED __attribute__((unused))
Index: libgcc/libgcov.c
===================================================================
--- libgcc/libgcov.c	(revision 187027)
+++ libgcc/libgcov.c	(working copy)
@@ -48,6 +48,7 @@
 #include "tm.h"
 #endif /* __KERNEL__ */
 #include "libgcc_tm.h"
+#include "gthr.h"

 #if 1
 #define THREAD_PREFIX __thread
@@ -668,6 +669,25 @@
   info->version = 0;
 }

+#ifdef __GTHREAD_MUTEX_INIT
+ATTRIBUTE_HIDDEN __gthread_mutex_t __gcov_flush_mx = __GTHREAD_MUTEX_INIT;
+#define init_mx_once()
+#else
+__gthread_mutex_t __gcov_flush_mx ATTRIBUTE_HIDDEN;
+
+static void
+init_mx (void)
+{
+  __GTHREAD_MUTEX_INIT_FUNCTION (&mx);
+}
+static void
+init_mx_once (void)
+{
+  static __gthread_once_t once = __GTHREAD_ONCE_INIT;
+  __gthread_once (&once, init_mx);
+}
+#endif
+
 /* Called before fork or exec - write out profile information gathered so
    far and reset it to zero.  This avoids duplication or loss of the
    profile information gathered so far.  */
@@ -677,6 +697,9 @@
 {
   const struct gcov_info *gi_ptr;

+  init_mx_once ();
+  __gthread_mutex_lock (&__gcov_flush_mx);
+
   __gcov_stop_pmu_profiler ();
   gcov_exit ();
   for (gi_ptr = __gcov_list; gi_ptr; gi_ptr = gi_ptr->next)
@@ -700,6 +723,7 @@
         }
     }
   __gcov_start_pmu_profiler ();
+  __gthread_mutex_unlock (&__gcov_flush_mx);
 }

 #else /* __GCOV_KERNEL__ */
@@ -1721,8 +1745,13 @@
 pid_t
 __gcov_fork (void)
 {
+  pid_t pid;
+  extern __gthread_mutex_t __gcov_flush_mx;
   __gcov_flush ();
-  return fork ();
+  pid = fork ();
+  if (pid == 0)
+    __GTHREAD_MUTEX_INIT_FUNCTION (&__gcov_flush_mx);
+  return pid;
 }
 #endif

Index: libgcc/unwind-dw2-fde.c
===================================================================
--- libgcc/unwind-dw2-fde.c	(revision 187027)
+++ libgcc/unwind-dw2-fde.c	(working copy)
@@ -47,11 +47,10 @@

 #ifdef __GTHREAD_MUTEX_INIT
 static __gthread_mutex_t object_mutex = __GTHREAD_MUTEX_INIT;
+#define init_object_mutex_once()
 #else
 static __gthread_mutex_t object_mutex;
-#endif

-#ifdef __GTHREAD_MUTEX_INIT_FUNCTION
 static void
 init_object_mutex (void)
 {
@@ -64,8 +63,6 @@
   static __gthread_once_t once = __GTHREAD_ONCE_INIT;
   __gthread_once (&once, init_object_mutex);
 }
-#else
-#define init_object_mutex_once()
 #endif

 /* Called from crtbegin.o to register the unwind info for an object.  */
Index: libgcc/gthr-posix.h
===================================================================
--- libgcc/gthr-posix.h	(revision 187027)
+++ libgcc/gthr-posix.h	(working copy)
@@ -63,6 +63,7 @@
 #define __GTHREAD_HAS_COND	1

 #define __GTHREAD_MUTEX_INIT PTHREAD_MUTEX_INITIALIZER
+#define __GTHREAD_MUTEX_INIT_FUNCTION __gthread_mutex_init_function
 #define __GTHREAD_ONCE_INIT PTHREAD_ONCE_INIT
 #if defined(PTHREAD_RECURSIVE_MUTEX_INITIALIZER)
 #define __GTHREAD_RECURSIVE_MUTEX_INIT PTHREAD_RECURSIVE_MUTEX_INITIALIZER
@@ -754,6 +755,14 @@
 #endif

 static inline int
+__gthread_mutex_init_function (__gthread_mutex_t *__mutex)
+{
+  if (__gthread_active_p ())
+    return __gthrw_(pthread_mutex_init) (__mutex, NULL);
+  return 0;
+}
+
+static inline int
 __gthread_mutex_destroy (__gthread_mutex_t *__mutex)
 {
   if (__gthread_active_p ())
Index: libgcc/gthr.h
===================================================================
--- libgcc/gthr.h	(revision 187027)
+++ libgcc/gthr.h	(working copy)
@@ -52,11 +52,12 @@
      		to initialize __gthread_mutex_t to get a fast
 		non-recursive mutex.
      __GTHREAD_MUTEX_INIT_FUNCTION
-     		some systems can't initialize a mutex without a
-		function call.  On such systems, define this to a
-		function which looks like this:
+		to initialize __gthread_mutex_t to get a fast
+		non-recursive mutex.
+		Define this to a function which looks like this:
 		  void __GTHREAD_MUTEX_INIT_FUNCTION (__gthread_mutex_t *)
-		Don't define __GTHREAD_MUTEX_INIT in this case
+     		Some systems can't initialize a mutex without a
+		function call.  Don't define __GTHREAD_MUTEX_INIT in this case.
      __GTHREAD_RECURSIVE_MUTEX_INIT
      __GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION
      		as above, but for a recursive mutex.

Follow-Ups:
- Re: Backported r185231 from trunk to google/gcc-4_7. (issue 6151043)
  - From: Xinliang David Li

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