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* [gcc r13-6282] [libstdc++] do not destruct mutex_pool mutexes
@ 2023-02-22 17:39 Alexandre Oliva
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From: Alexandre Oliva @ 2023-02-22 17:39 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:d70f49e98245f80fcf8b2e68a9f06955f52e1de7
commit r13-6282-gd70f49e98245f80fcf8b2e68a9f06955f52e1de7
Author: Alexandre Oliva <oliva@adacore.com>
Date: Wed Feb 22 14:35:18 2023 -0300
[libstdc++] do not destruct mutex_pool mutexes
On vxworks, after destroying the semaphore used to implement a mutex,
__gthread_mutex_lock fails and __gnu_cxx::__mutex::lock calls
__throw_concurrence_lock_error. Nothing ensures the mutex_pool
mutexes survive init-once objects containing _Safe_sequence_base. If
such an object completes construction before mutex_pool
initialization, it will be registered for atexit destruction after the
mutex_pool mutexes, so the _M_detach_all() call in the
_Safe_sequence_base dtor will use already-destructed mutexes, and
basic_string/requirements/citerators_cc fails calling terminate.
This patch fixes this problem by ensuring the mutex pool mutexes are
constructed on demand, on a statically-allocated buffer, but never
destructed.
for libstdc++-v3/ChangeLog
* src/c++11/shared_ptr.cc (__gnu_internal::get_mutex):
Avoid destruction of the mutex pool.
Diff:
---
libstdc++-v3/src/c++11/shared_ptr.cc | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/libstdc++-v3/src/c++11/shared_ptr.cc b/libstdc++-v3/src/c++11/shared_ptr.cc
index bc70134359c..74e879e5828 100644
--- a/libstdc++-v3/src/c++11/shared_ptr.cc
+++ b/libstdc++-v3/src/c++11/shared_ptr.cc
@@ -36,7 +36,11 @@ namespace __gnu_internal _GLIBCXX_VISIBILITY(hidden)
{
// increase alignment to put each lock on a separate cache line
struct alignas(64) M : __gnu_cxx::__mutex { };
- static M m[mask + 1];
+ // Use a static buffer, so that the mutexes are not destructed
+ // before potential users (or at all)
+ static __attribute__ ((aligned(__alignof__(M))))
+ char buffer[(sizeof (M)) * (mask + 1)];
+ static M *m = new (buffer) M[mask + 1];
return m[i];
}
}
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