Change the control flow in atomic_compare_exchange_strong to avoid a potential deadlock.
When you assign a shared_ptr, the deleter gets called and assigned. In this routine, the assignment happens inside a critical section, which could (potentially) lead to a deadlock, if the deleter did something wonky. Now we swap the old value with an (empty) temporary shared_ptr, and then let the temporary delete the old value when it goes out of scope (after the lock has been released). This should fix PR#27724. Thanks to Hans Boehm for the bug report and the suggested fix.
llvm-svn: 269965
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 3379baeb99a9045bffc0ac9b8e3a5b35c640e707
diff --git a/include/memory b/include/memory
index 8378aef..7627248 100644
--- a/include/memory
+++ b/include/memory
@@ -5541,14 +5541,17 @@
bool
atomic_compare_exchange_strong(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w)
{
+ shared_ptr<_Tp> __temp;
__sp_mut& __m = __get_sp_mut(__p);
__m.lock();
if (__p->__owner_equivalent(*__v))
{
+ _VSTD::swap(__temp, *__p);
*__p = __w;
__m.unlock();
return true;
}
+ _VSTD::swap(__temp, *__v);
*__v = *__p;
__m.unlock();
return false;