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authorPaolo Bonzini <pbonzini@redhat.com>2015-03-05 16:47:14 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2015-03-10 10:49:25 +0100
commit24fa90499f8b24bcba2960a3316d797f9b80b5e9 (patch)
tree4e93359844894cf44e1799deb2accf541cccb6a1
parent811c5727765eba00824c29a696350d4780d86c19 (diff)
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qemu-thread: do not use PTHREAD_MUTEX_ERRORCHECK
PTHREAD_MUTEX_ERRORCHECK is completely broken with respect to fork. The way to safely do fork is to bring all threads to a quiescent state by acquiring locks (either in callers---as we do for the iothread mutex---or using pthread_atfork's prepare callbacks) and then release them in the child. The problem is that releasing error-checking locks in the child fails under glibc with EPERM, because the mutex stores a different owner tid than the duplicated thread in the child process. We could make it work for locks acquired via pthread_atfork, by recreating the mutex in the child instead of unlocking it (we know that there are no other threads that could have taken the mutex; but when the lock is acquired in fork's caller that would not be possible. The simplest solution is just to forgo error checking. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--util/qemu-thread-posix.c6
1 files changed, 1 insertions, 5 deletions
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index 50a29d8..ba67cec 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -51,12 +51,8 @@ static void error_exit(int err, const char *msg)
void qemu_mutex_init(QemuMutex *mutex)
{
int err;
- pthread_mutexattr_t mutexattr;
- pthread_mutexattr_init(&mutexattr);
- pthread_mutexattr_settype(&mutexattr, PTHREAD_MUTEX_ERRORCHECK);
- err = pthread_mutex_init(&mutex->lock, &mutexattr);
- pthread_mutexattr_destroy(&mutexattr);
+ err = pthread_mutex_init(&mutex->lock, NULL);
if (err)
error_exit(err, __func__);
}