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qemu-thread: add per-thread atexit functions

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Destructors are the main additional feature of pthread TLS compared
to __thread.  If we were using C++ (hint, hint!) we could have used
thread-local objects with a destructor.  Since we are not, instead,
we add a simple Notifier-based API.

Note that the notifier must be per-thread as well.  We can add a
global list as well later, perhaps.

The Win32 implementation has some complications because a) detached
threads used not to have a QemuThreadData; b) the main thread does
not go through win32_start_routine, so we have to use atexit too.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 1417518350-6167-3-git-send-email-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Paolo Bonzini 2014-12-02 12:05:45 +01:00 • committed by Stefan Hajnoczi
parent d1d1b206b0
commit ef57137f1b
3 changed files with 78 additions and 11 deletions
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37
util/qemu-thread-posix.c
View file

@ -26,6 +26,7 @@
#endif
#include "qemu/thread.h"
#include "qemu/atomic.h"
#include "qemu/notify.h"
static bool name_threads;
@ -401,6 +402,42 @@ void qemu_event_wait(QemuEvent *ev)
}
}
static pthread_key_t exit_key;
union NotifierThreadData {
void *ptr;
NotifierList list;
};
QEMU_BUILD_BUG_ON(sizeof(union NotifierThreadData) != sizeof(void *));
void qemu_thread_atexit_add(Notifier *notifier)
{
union NotifierThreadData ntd;
ntd.ptr = pthread_getspecific(exit_key);
notifier_list_add(&ntd.list, notifier);
pthread_setspecific(exit_key, ntd.ptr);
}
void qemu_thread_atexit_remove(Notifier *notifier)
{
union NotifierThreadData ntd;
ntd.ptr = pthread_getspecific(exit_key);
notifier_remove(notifier);
pthread_setspecific(exit_key, ntd.ptr);
}
static void qemu_thread_atexit_run(void *arg)
{
union NotifierThreadData ntd = { .ptr = arg };
notifier_list_notify(&ntd.list, NULL);
}
static void __attribute__((constructor)) qemu_thread_atexit_init(void)
{
pthread_key_create(&exit_key, qemu_thread_atexit_run);
}
/* Attempt to set the threads name; note that this is for debug, so
* we're not going to fail if we can't set it.
*/