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From: "Joost.VandeVondele at mat dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug sanitizer/55561] TSAN: Fortran/OMP yields false positives
Date: Tue, 01 Jan 2013 17:14:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55561

--- Comment #28 from Joost VandeVondele <Joost.VandeVondele at mat dot ethz.ch> 2013-01-01 17:13:39 UTC ---
(In reply to comment #26)
> For config/linux/ptrlock the changes are:
> [...]

Following your suggestions, I applied the following patch (mistakes are mine),
which allows me to run without warnings from libgomp:

Index: config/linux/wait.h
===================================================================
--- config/linux/wait.h (revision 194730)
+++ config/linux/wait.h (working copy)
@@ -51,7 +51,7 @@
   if (__builtin_expect (gomp_managed_threads > gomp_available_cpus, 0))
     count = gomp_throttled_spin_count_var;
   for (i = 0; i < count; i++)
-    if (__builtin_expect (*addr != val, 0))
+    if (__builtin_expect (__atomic_load_n(addr,MEMMODEL_RELAXED) != val, 0))
       return 0;
     else
       cpu_relax ();
Index: config/linux/ptrlock.c
===================================================================
--- config/linux/ptrlock.c      (revision 194730)
+++ config/linux/ptrlock.c      (working copy)
@@ -50,9 +50,9 @@
 #endif
   do
     do_wait (intptr, 2);
-  while (*intptr == 2);
+  while (__atomic_load_n(intptr, MEMMODEL_RELAXED) == 2);
   __asm volatile ("" : : : "memory");
-  return *ptrlock;
+  return (void*)__atomic_load_n(ptrlock, MEMMODEL_ACQUIRE);
 }

 void
Index: config/linux/ptrlock.h
===================================================================
--- config/linux/ptrlock.h      (revision 194730)
+++ config/linux/ptrlock.h      (working copy)
@@ -48,8 +48,9 @@
 {
   uintptr_t oldval;

-  if ((uintptr_t) *ptrlock > 2)
-    return *ptrlock;
+  uintptr_t v = (uintptr_t)__atomic_load_n(ptrlock, MEMMODEL_ACQUIRE);
+  if (v > 2)
+    return (void*)v;

   oldval = 0;
   if (__atomic_compare_exchange_n (ptrlock, &oldval, 1, false,