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Re: [Qemu-devel] Help with deadlock when using sound
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] Help with deadlock when using sound |
Date: |
Wed, 13 May 2015 10:38:10 +0100 |
On 13 May 2015 at 04:23, Programmingkid <address@hidden> wrote:
> Found out why QEMU is deadlocking. It is because a mutex that has been
> unlocked over 20 times in a row is being locked.
OSX supports 'error checking' mutexes which will fail in these
undefined-behaviour cases like double-unlock. (The error checking
slows things down which is why it's not the default). If you make
qemu_mutex_init() something like:
void qemu_mutex_init(QemuMutex *mutex)
{
int err;
pthread_mutexattr_t mta;
err = pthread_mutexattr_init(&mta);
if (err) {
error_exit(err, __func__);
}
err = pthread_mutexattr_settype(&mta, PTHREAD_MUTEX_ERRORCHECK);
if (err) {
error_exit(err, __func__);
}
err = pthread_mutex_init(&mutex->lock, &mta);
if (err) {
error_exit(err, __func__);
}
pthread_mutexattr_destroy(&mta);
if (err) {
error_exit(err, __func__);
}
}
then we'll turn on the error checking, and a double-unlock
will result in a call to abort(). If you run QEMU under
a debugger you'll get a backtrace which will tell you which
code did the second unlock (and thus which mutex it is).
(Linux has a similar attribute, though it is named
PTHREAD_MUTEX_ERRORCHECK_NP; we might want to consider
turning on mutex debugging for --enable-debug builds.)
-- PMM
Re: [Qemu-devel] Help with deadlock when using sound, Paolo Bonzini, 2015/05/10
- Re: [Qemu-devel] Help with deadlock when using sound, Paolo Bonzini, 2015/05/10
- Re: [Qemu-devel] Help with deadlock when using sound, Programmingkid, 2015/05/10
- Re: [Qemu-devel] Help with deadlock when using sound, Programmingkid, 2015/05/11
- Re: [Qemu-devel] Help with deadlock when using sound, Paolo Bonzini, 2015/05/12
- Re: [Qemu-devel] Help with deadlock when using sound, Programmingkid, 2015/05/12
- Re: [Qemu-devel] Help with deadlock when using sound, Programmingkid, 2015/05/12
- Re: [Qemu-devel] Help with deadlock when using sound,
Peter Maydell <=
- Re: [Qemu-devel] Help with deadlock when using sound, Programmingkid, 2015/05/13
- Re: [Qemu-devel] Help with deadlock when using sound, Peter Maydell, 2015/05/13
- Re: [Qemu-devel] Help with deadlock when using sound, Paolo Bonzini, 2015/05/13
Re: [Qemu-devel] Help with deadlock when using sound, Programmingkid, 2015/05/10