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SubjectRe: [PATCH V5] futex: set FLAGS_HAS_TIMEOUT during futex_wait restart setup
On Thu, 14 Apr 2011, Darren Hart wrote:

> The FLAGS_HAS_TIMEOUT flag was not getting set, causing the restart_block to
> restart futex_wait() without a timeout after a signal.
>
> Commit b41277dc7a18ee332d in 2.6.38 introduced the regression by accidentally
> removing the the FLAGS_HAS_TIMEOUT assignment from futex_wait() during the setup
> of the restart block. Restore the originaly behavior.
>
> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=32922
>
> V2: Added references to commit message.
> V3: Set flag during restart block instead of do_futex()
> V4: Correct stupid order of assignment mistake pointed out by Eric
> V5: Correct subject to match implementation, correct stable submission
>
> Signed-off-by: Darren Hart <dvhart@linux.intel.com>
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> Reported-by: Tim Smith <tsmith201104@yahoo.com>
> Reported-by: Torsten Hilbrich <torsten.hilbrich@secunet.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: John Kacur <jkacur@redhat.com>
> Cc: stable@kernel.org
> ---
> kernel/futex.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/futex.c b/kernel/futex.c
> index bda4157..abd5324 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -1886,7 +1886,7 @@ retry:
> restart->futex.val = val;
> restart->futex.time = abs_time->tv64;
> restart->futex.bitset = bitset;
> - restart->futex.flags = flags;
> + restart->futex.flags = flags | FLAGS_HAS_TIMEOUT;

We only get here when a timeout is pending. So why don't we just do
the obvious:

--- linux-2.6.orig/kernel/futex.c
+++ linux-2.6/kernel/futex.c
@@ -1902,16 +1902,13 @@ out:
static long futex_wait_restart(struct restart_block *restart)
{
u32 __user *uaddr = restart->futex.uaddr;
- ktime_t t, *tp = NULL;
+ ktime_t t;

- if (restart->futex.flags & FLAGS_HAS_TIMEOUT) {
- t.tv64 = restart->futex.time;
- tp = &t;
- }
+ t.tv64 = restart->futex.time;
restart->fn = do_no_restart_syscall;

return (long)futex_wait(uaddr, restart->futex.flags,
- restart->futex.val, tp, restart->futex.bitset);
+ restart->futex.val, &t, restart->futex.bitset);
}

Thanks,

tglx

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