From 337f13046ff03717a9e99675284a817527440a49 Mon Sep 17 00:00:00 2001
From: Darren Hart <dvhart@linux.intel.com>
Date: Fri, 18 Dec 2015 13:36:37 -0800
Subject: [PATCH] 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>
---
kernel/futex.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index 461d438f48161..8a310e240cdaf 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -3084,7 +3084,8 @@ long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
if (op & FUTEX_CLOCK_REALTIME) {
flags |= FLAGS_CLOCKRT;
- if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI)
+ if (cmd != FUTEX_WAIT && cmd != FUTEX_WAIT_BITSET && \
+ cmd != FUTEX_WAIT_REQUEUE_PI)
return -ENOSYS;
}
--
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