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diff -pruN glibc-2.17-c758a686/nptl/sysdeps/pthread/unwind-forcedunwind.c glibc-2.17-c758a686/nptl/sysdeps/pthread/unwind-forcedunwind.c
--- glibc-2.17-c758a686/nptl/sysdeps/pthread/unwind-forcedunwind.c 2010-05-04 16:57:23.000000000 +0530
+++ glibc-2.17-c758a686/nptl/sysdeps/pthread/unwind-forcedunwind.c 2014-06-02 23:00:02.901013275 +0530
@@ -45,8 +45,10 @@ pthread_cancel_init (void)
if (__builtin_expect (libgcc_s_handle != NULL, 1))
{
- /* Force gcc to reload all values. */
- asm volatile ("" ::: "memory");
+ /* Order reads so as to prevent speculation of loads
+ of libgcc_s_{resume,personality,forcedunwind,getcfa}
+ to points prior to the write barrier. */
+ atomic_read_barrier ();
return;
}
@@ -72,9 +74,14 @@ pthread_cancel_init (void)
libgcc_s_forcedunwind = forcedunwind;
PTR_MANGLE (getcfa);
libgcc_s_getcfa = getcfa;
- /* Make sure libgcc_s_handle is written last. Otherwise,
- pthread_cancel_init might return early even when the pointer the
- caller is interested in is not initialized yet. */
+ /* At the point at which any thread writes the handle
+ to libgcc_s_handle, the initialization is complete.
+ The writing of libgcc_s_handle is atomic. All other
+ threads reading libgcc_s_handle do so atomically. Any
+ thread that does not execute this function must issue
+ a read barrier to ensure that all of the above has
+ actually completed and that the values of the
+ function pointers are correct. */
atomic_write_barrier ();
libgcc_s_handle = handle;
}
@@ -91,13 +98,19 @@ __unwind_freeres (void)
}
}
-void
-_Unwind_Resume (struct _Unwind_Exception *exc)
+static __always_inline void
+_maybe_pthread_cancel_init (void)
{
if (__builtin_expect (libgcc_s_handle == NULL, 0))
pthread_cancel_init ();
else
atomic_read_barrier ();
+}
+
+void
+_Unwind_Resume (struct _Unwind_Exception *exc)
+{
+ _maybe_pthread_cancel_init ();
void (*resume) (struct _Unwind_Exception *exc) = libgcc_s_resume;
PTR_DEMANGLE (resume);
@@ -108,10 +123,7 @@ __gcc_personality_v0 (int version, _Unwi
struct _Unwind_Exception *ue_header,
struct _Unwind_Context *context)
{
- if (__builtin_expect (libgcc_s_handle == NULL, 0))
- pthread_cancel_init ();
- else
- atomic_read_barrier ();
+ _maybe_pthread_cancel_init ();
_Unwind_Reason_Code (*personality)
(int, _Unwind_Action, _Unwind_Exception_Class, struct _Unwind_Exception *,
@@ -122,10 +136,7 @@ _Unwind_Reason_Code
_Unwind_ForcedUnwind (struct _Unwind_Exception *exc, _Unwind_Stop_Fn stop,
void *stop_argument)
{
- if (__builtin_expect (libgcc_s_handle == NULL, 0))
- pthread_cancel_init ();
- else
- atomic_read_barrier ();
+ _maybe_pthread_cancel_init ();
_Unwind_Reason_Code (*forcedunwind)
(struct _Unwind_Exception *, _Unwind_Stop_Fn, void *)
@@ -135,10 +148,7 @@ _Unwind_ForcedUnwind (struct _Unwind_Exc
_Unwind_Word
_Unwind_GetCFA (struct _Unwind_Context *context)
{
- if (__builtin_expect (libgcc_s_handle == NULL, 0))
- pthread_cancel_init ();
- else
- atomic_read_barrier ();
+ _maybe_pthread_cancel_init ();
_Unwind_Word (*getcfa) (struct _Unwind_Context *) = libgcc_s_getcfa;
PTR_DEMANGLE (getcfa);
diff -pruN glibc-2.17-c758a686/sysdeps/gnu/unwind-resume.c glibc-2.17-c758a686/sysdeps/gnu/unwind-resume.c
--- glibc-2.17-c758a686/sysdeps/gnu/unwind-resume.c 2010-05-04 16:57:23.000000000 +0530
+++ glibc-2.17-c758a686/sysdeps/gnu/unwind-resume.c 2014-06-02 23:02:26.812007078 +0530
@@ -20,8 +20,11 @@
#include <dlfcn.h>
#include <stdio.h>
#include <unwind.h>
+#include <pthreadP.h>
+#include <sysdep.h>
#include <gnu/lib-names.h>
+static void *libgcc_s_handle;
static void (*libgcc_s_resume) (struct _Unwind_Exception *exc);
static _Unwind_Reason_Code (*libgcc_s_personality)
(int, _Unwind_Action, _Unwind_Exception_Class, struct _Unwind_Exception *,
@@ -42,13 +45,32 @@ init (void)
libgcc_s_resume = resume;
libgcc_s_personality = personality;
+ atomic_write_barrier ();
+ /* At the point at which any thread writes the handle
+ to libgcc_s_handle, the initialization is complete.
+ The writing of libgcc_s_handle is atomic. All other
+ threads reading libgcc_s_handle do so atomically. Any
+ thread that does not execute this function must issue
+ a read barrier to ensure that all of the above has
+ actually completed and that the values of the
+ function pointers are correct. */
+ libgcc_s_handle = handle;
}
+static __always_inline void
+_maybe_init (void)
+{
+ if (__builtin_expect (libgcc_s_handle == NULL, 0))
+ init ();
+ else
+ atomic_read_barrier ();
+}
+
+
void
_Unwind_Resume (struct _Unwind_Exception *exc)
{
- if (__builtin_expect (libgcc_s_resume == NULL, 0))
- init ();
+ _maybe_init ();
libgcc_s_resume (exc);
}
@@ -58,8 +80,7 @@ __gcc_personality_v0 (int version, _Unwi
struct _Unwind_Exception *ue_header,
struct _Unwind_Context *context)
{
- if (__builtin_expect (libgcc_s_personality == NULL, 0))
- init ();
+ _maybe_init ();
return libgcc_s_personality (version, actions, exception_class,
ue_header, context);
}