[Bug gcov-profile/97461] [11 Regression] allocate_gcov_kvp() deadlocks in firefox LTO+PGO build (overridden malloc() recursion)

["marxin at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97461

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW

--- Comment #23 from Martin Liška <marxin at gcc dot gnu.org> ---
Thank you for the testing. Neither of the suggested changes help us.
The core issue is that gcov does not know if it's called from a free/malloc
function.

That said, I see currently 2 possible fixes:

1. help from a malloc library that uses
__gcov_supress_malloc/__gcov_allow_malloc:

commit ee382a226ba0e76e2242dcbb4768033a4809a890
Author: Martin Liska <mliska@suse.cz>
Date:   Fri Nov 6 16:59:43 2020 +0100

    WIP patch.

diff --git a/libgcc/Makefile.in b/libgcc/Makefile.in
index d6075d32bd4..b235231f9d6 100644
--- a/libgcc/Makefile.in
+++ b/libgcc/Makefile.in
@@ -907,7 +907,7 @@ LIBGCOV_PROFILER = _gcov_interval_profiler                 
        \
 LIBGCOV_INTERFACE = _gcov_dump _gcov_fork                              \
        _gcov_execl _gcov_execlp                                        \
        _gcov_execle _gcov_execv _gcov_execvp _gcov_execve _gcov_reset  \
-       _gcov_lock_unlock
+       _gcov_lock_unlock _gcov_supress_malloc _gcov_allow_malloc
 LIBGCOV_DRIVER = _gcov

 libgcov-merge-objects = $(patsubst %,%$(objext),$(LIBGCOV_MERGE))
diff --git a/libgcc/gcov.h b/libgcc/gcov.h
index 0e3eed31032..444f996692e 100644
--- a/libgcc/gcov.h
+++ b/libgcc/gcov.h
@@ -33,4 +33,12 @@ extern void __gcov_reset (void);

 extern void __gcov_dump (void);

+/* Prevent from calling malloc.  */
+
+extern void __gcov_supress_malloc (void);
+
+/* Allow calling malloc.  */
+
+extern void __gcov_allow_malloc (void);
+
 #endif /* GCC_GCOV_H */
diff --git a/libgcc/libgcov-interface.c b/libgcc/libgcov-interface.c
index 3a8a5bf44b8..bcfc38b85c3 100644
--- a/libgcc/libgcov-interface.c
+++ b/libgcc/libgcov-interface.c
@@ -36,6 +36,14 @@ void __gcov_reset (void) {}
 void __gcov_dump (void) {}
 #endif

+#ifdef L_gcov_supress_malloc
+void __gcov_supress_malloc (void) {}
+#endif
+
+#ifdef L_gcov_allow_malloc
+void __gcov_allow_malloc (void) {}
+#endif
+
 #else

 extern __gthread_mutex_t __gcov_mx ATTRIBUTE_HIDDEN;
@@ -174,6 +182,20 @@ __gcov_dump (void)

 #endif /* L_gcov_dump */

+#ifdef L_gcov_supress_malloc
+void __gcov_supress_malloc (void)
+{
+  __gcov_block_malloc = 1;
+}
+#endif /* L_gcov_supress_malloc */
+
+#ifdef L_gcov_allow_malloc
+void __gcov_allow_malloc (void)
+{
+  __gcov_block_malloc = 0;
+}
+#endif /* L_gcov_block_malloc */
+
 #ifdef L_gcov_fork
 /* A wrapper for the fork function.  We reset counters in the child
    so that they are not counted twice.  */
diff --git a/libgcc/libgcov-profiler.c b/libgcc/libgcov-profiler.c
index 45ab93c9776..b83b230cd9c 100644
--- a/libgcc/libgcov-profiler.c
+++ b/libgcc/libgcov-profiler.c
@@ -141,6 +141,12 @@ __thread
 #endif
 struct indirect_call_tuple __gcov_indirect_call;

+// TODO: move to a proper place
+#if defined(HAVE_CC_TLS) && !defined (USE_EMUTLS)
+__thread
+#endif
+int __gcov_block_malloc;
+
 /* By default, the C++ compiler will use function addresses in the
    vtable entries.  Setting TARGET_VTABLE_USES_DESCRIPTORS to nonzero
    tells the compiler to use function descriptors instead.  The value
diff --git a/libgcc/libgcov.h b/libgcc/libgcov.h
index e70cf63b414..2eaed9548ea 100644
--- a/libgcc/libgcov.h
+++ b/libgcc/libgcov.h
@@ -247,6 +247,12 @@ struct indirect_call_tuple
   /* Pointer to counters.  */
   gcov_type *counters;
 };
+
+extern
+#if defined(HAVE_CC_TLS) && !defined (USE_EMUTLS)
+__thread
+#endif
+int __gcov_block_malloc;

 /* Exactly one of these will be active in the process.  */
 extern struct gcov_master __gcov_master;
@@ -428,7 +434,12 @@ allocate_gcov_kvp (void)
 #endif

   if (new_node == NULL)
-    new_node = (struct gcov_kvp *)xcalloc (1, sizeof (struct gcov_kvp));
+    {
+#if !defined(IN_GCOV_TOOL)
+      if (!__gcov_block_malloc)
+       new_node = (struct gcov_kvp *)xcalloc (1, sizeof (struct gcov_kvp));
+#endif
+    }

   return new_node;
 }

2) make a dynamic allocation for counters for TOPN at the very beginning in
__gcov_init.

@Honza: What do you think about it?