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Fix workaround in pthread destructor

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Amends dcdfb6908db0f83cbc4e550859f56ee58a6b3420 which failed to take the
workaround in destroy_current_thread_data into account.

Since pthread_getspecific was completely replaced with the thread_local variable
currentThreadData, the workaround has no effect anymore. Therefore we need to
replace it with a workaround that makes sure currentThreadData is set inside of
the destructor function.

This prevents a leak, where QThreadPrivate::finish() tries to access the
thread data, but since it already is null, recreates it without ever deleting it.

Pick-to: 5.15
Change-Id: I3811d262a411a6bde9d6eb90f8d17e0bbc5de657
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Mike Achtelik 2020-07-03 10:13:58 +02:00
parent f172f0dee9
commit 90f1ef14aa
1 changed files with 6 additions and 19 deletions
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25
src/corelib/thread/qthread_unix.cpp
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@ -116,18 +116,11 @@ static pthread_key_t current_thread_data_key;
static void destroy_current_thread_data(void *p) static void destroy_current_thread_data(void *p)
{ {
#if defined(Q_OS_VXWORKS)
// Calling setspecific(..., 0) sets the value to 0 for ALL threads.
// The 'set to 1' workaround adds a bit of an overhead though,
// since this function is called twice now.
if (p == (void *)1)
return;
#endif
// POSIX says the value in our key is set to zero before calling
// this destructor function, so we need to set it back to the
// right value...
pthread_setspecific(current_thread_data_key, p);
QThreadData *data = static_cast<QThreadData *>(p); QThreadData *data = static_cast<QThreadData *>(p);
// thread_local variables are set to zero before calling this destructor function,
// if they are internally using pthread-specific data management,
// so we need to set it back to the right value...
currentThreadData = data;
if (data->isAdopted) { if (data->isAdopted) {
QThread *thread = data->thread.loadAcquire(); QThread *thread = data->thread.loadAcquire();
Q_ASSERT(thread); Q_ASSERT(thread);
@ -138,14 +131,8 @@ static void destroy_current_thread_data(void *p)
data->deref(); data->deref();
// ... but we must reset it to zero before returning so we aren't // ... but we must reset it to zero before returning so we aren't
// called again (POSIX allows implementations to call destructor // leaving a dangling pointer.
// functions repeatedly until all values are zero) currentThreadData = nullptr;
pthread_setspecific(current_thread_data_key,
#if defined(Q_OS_VXWORKS)
(void *)1);
#else
nullptr);
#endif
} }
static void create_current_thread_data_key() static void create_current_thread_data_key()