Messages in this thread | | | Date | Thu, 12 Mar 2009 08:15:38 -0700 | From | Darren Hart <> | Subject | Re: [PATCH 5/6] futex: unlock before returning -EFAULT |
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Peter Zijlstra wrote: > 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. >
OK, are there any other concerns with this patch?
-- Darren Hart IBM Linux Technology Center Real-Time Linux Team
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