Messages in this thread | | | Subject | Re: [PATCH 5/6] futex: unlock before returning -EFAULT | From | Peter Zijlstra <> | Date | Thu, 12 Mar 2009 12:06:57 +0100 |
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On Thu, 2009-03-12 at 11:47 +0100, Thomas Gleixner wrote: > On Thu, 12 Mar 2009, Peter Zijlstra wrote: > > > On Thu, 2009-03-12 at 00:56 -0700, Darren Hart wrote: > > > futex_lock_pi can potentially return -EFAULT with the rt_mutex held. This > > > seems like the wrong thing to do as userspace should assume -EFAULT means the > > > lock was not taken. Even if it could figure this out, we'd be leaving the > > > pi_state->owner in an inconsistent state. This patch unlocks the rt_mutex > > > prior to returning -EFAULT to userspace. > > > > lockdep would complain, one is not to leave the kernel with locks held. > > That would break pi futexes in bits and pieces. > > T1 takes F1 > T2 blocks on F1 > -> T2 sets up rt_mutex and locks it for T1 > T2 blocks on rt_mutex and boosts T1 > > T1 calls a non futex syscall > T1 returns from syscall with the rt_mutex still locked > > Thanks,
Oh right, raw rt_mutex stuff isn't lockdep annotated, and you use the robust futex infrastructure to ensure stuff gets unlocked when holder dies. That should work out.
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