futex: Allow FUTEX_CLOCK_REALTIME with FUTEX_WAIT op
While reviewing Michael Kerrisk's recent futex manpage update, I noticed that we allow the FUTEX_CLOCK_REALTIME flag for FUTEX_WAIT_BITSET but not for FUTEX_WAIT. FUTEX_WAIT is treated as a simple version for FUTEX_WAIT_BITSET internally (with a bitmask of FUTEX_BITSET_MATCH_ANY). As such, I cannot come up with a reason for this exclusion for FUTEX_WAIT. This change does modify the behavior of the futex syscall, changing a call with FUTEX_WAIT | FUTEX_CLOCK_REALTIME from returning -ENOSYS, to be equivalent to FUTEX_WAIT_BITSET | FUTEX_CLOCK_REALTIME with a bitset of FUTEX_BITSET_MATCH_ANY. Reported-by: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: Darren Hart <dvhart@linux.intel.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Link: http://lkml.kernel.org/r/9f3bdc116d79d23f5ee72ceb9a2a857f5ff8fa29.1450474525.git.dvhart@linux.intel.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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@ -3084,7 +3084,8 @@ long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
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if (op & FUTEX_CLOCK_REALTIME) {
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if (op & FUTEX_CLOCK_REALTIME) {
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flags |= FLAGS_CLOCKRT;
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flags |= FLAGS_CLOCKRT;
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if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI)
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if (cmd != FUTEX_WAIT && cmd != FUTEX_WAIT_BITSET && \
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cmd != FUTEX_WAIT_REQUEUE_PI)
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return -ENOSYS;
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return -ENOSYS;
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}
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}
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