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authorThomas Gleixner <tglx@linutronix.de>2009-10-13 14:40:43 -0400
committerThomas Gleixner <tglx@linutronix.de>2009-10-13 14:40:43 -0400
commitd58e6576b0deec6f0b9ff8450fe282da18c50883 (patch)
treed4838a745f90e60057194169cea796584946202e /Documentation/video4linux/et61x251.txt
parentc7cedb125ba20cc531671dc667ad704baa667d97 (diff)
futex: Handle spurious wake up
The futex code does not handle spurious wake up in futex_wait and futex_wait_requeue_pi. The code assumes that any wake up which was not caused by futex_wake / requeue or by a timeout was caused by a signal wake up and returns one of the syscall restart error codes. In case of a spurious wake up the signal delivery code which deals with the restart error codes is not invoked and we return that error code to user space. That causes applications which actually check the return codes to fail. Blaise reported that on preempt-rt a python test program run into a exception trap. -rt exposed that due to a built in spurious wake up accelerator :) Solve this by checking signal_pending(current) in the wake up path and handle the spurious wake up case w/o returning to user space. Reported-by: Blaise Gassend <blaise@willowgarage.com> Debugged-by: Darren Hart <dvhltc@us.ibm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: stable@kernel.org LKML-Reference: <new-submission>
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