Messages in this thread | | | From | david singleton <> | Subject | Re: Recursion bug in -rt | Date | Mon, 2 Jan 2006 17:54:43 -0800 |
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Dinakar, can you try patch-2.6.15-rc7-rt3-rf1 on http://source.mvista.com/~dsingleton/ and see if it works for your tests?
This new patch creates a 'futex_deadlock' semaphore that we hang applications that are deadlocking themselves. This method will only hang the application, not the system, as no other locks are held, like the mmap_sem, just the futex_deadlock semaphore.
NOTE: for pthread_mutexes that are robust but NOT POSIX priority inheriting I return -EWOULDDEADLOCK, since there is no POSIX specfication for robust pthread_mutexes yet. POSIX PI pthread_mutexes will hang on the futex_deadlock semaphore.
Let me know how it works.
David
On Dec 20, 2005, at 7:50 AM, Dinakar Guniguntala wrote:
> On Tue, Dec 20, 2005 at 02:19:56PM +0100, Ingo Molnar wrote: >> >> hm, i'm looking at -rf4 - these changes look fishy: >> >> - _raw_spin_lock(&lock_owner(lock)->task->pi_lock); >> + if (current != lock_owner(lock)->task) >> + _raw_spin_lock(&lock_owner(lock)->task->pi_lock); >> >> why is this done? >> > > Ingo, this is to prevent a kernel hang due to application error. > > Basically when an application does a pthread_mutex_lock twice on a > _nonrecursive_ mutex with robust/PI attributes the whole system hangs. > Ofcourse the application clearly should not be doing anything like > that, but it should not end up hanging the system either > > -Dinakar >
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