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authorThomas Gleixner <tglx@linutronix.de>2009-10-28 20:26:48 +0100
committerThomas Gleixner <tglx@linutronix.de>2009-10-28 20:34:34 +0100
commit11df6dddcbc38affb7473aad3d962baf8414a947 (patch)
treefb05ef2583a55e69897988491522b92137ca5f26 /kernel/user.c
parent89061d3d58e1f0742139605dc6a7950aa1ecc019 (diff)
futex: Fix spurious wakeup for requeue_pi really
The requeue_pi path doesn't use unqueue_me() (and the racy lock_ptr == NULL test) nor does it use the wake_list of futex_wake() which where the reason for commit 41890f2 (futex: Handle spurious wake up) See debugging discussing on LKML Message-ID: <4AD4080C.20703@us.ibm.com> The changes in this fix to the wait_requeue_pi path were considered to be a likely unecessary, but harmless safety net. But it turns out that due to the fact that for unknown $@#!*( reasons EWOULDBLOCK is defined as EAGAIN we built an endless loop in the code path which returns correctly EWOULDBLOCK. Spurious wakeups in wait_requeue_pi code path are unlikely so we do the easy solution and return EWOULDBLOCK^WEAGAIN to user space and let it deal with the spurious wakeup. Cc: Darren Hart <dvhltc@us.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: John Stultz <johnstul@linux.vnet.ibm.com> Cc: Dinakar Guniguntala <dino@in.ibm.com> LKML-Reference: <4AE23C74.1090502@us.ibm.com> Cc: stable@kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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