On 05/14/2014 06:28 AM, Thomas Gleixner wrote: > On Wed, 14 May 2014, Peter Zijlstra wrote: >> On Wed, May 14, 2014 at 11:53:44AM +0200, Thomas Gleixner wrote: >>>> What error would we return? >>>> >>>> This particular case is a serious error for which we have no good error >>>> code >>>> to return to userspace. It's an implementation defect, a bug, we should >>>> probably >>>> assert instead of pausing. >>> >>> Errm. >>> >>> http://pubs.opengroup.org/onlinepubs/7908799/xsh/pthread_mutex_lock.html >>> >>> The pthread_mutex_lock() function may fail if: >>> >>> [EDEADLK] >>> The current thread already owns the mutex. >>> >>> That's a exactly the error code, which the kernel returns when it >>> detects a deadlock. >>> >>> And glibc returns EDEADLK at a lot of places already. So in that case >>> it's not a serious error? Because it's detected by glibc. You can't be >>> serious about that. >>> >>> So why is a kernel detected deadlock different? Because it detects not >>> only AA, it detects ABBA and more. But it's still a dead lock. And >>> while posix spec only talks about AA, it's the very same issue. >>> >>> So why not propagate this to the caller so he gets an alert right away >>> instead of letting him attach a debugger, and scratch his head and >>> lookup glibc source to find out why the hell glibc called pause. >> >> >> http://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_mutex_lock.html > > Yuck. I should not have used the first link Gurgle brought up.
For the record the correct link is for POSIX Issue 7 (Issue 8 under development). http://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_mutex_lock.html The Issue 7 version has a nice table :} Cheers, Carlos. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
