Just curious, any particular reason you want to backport this patch?
because nobody understands why it actually helped.
and please note that this patch is buggy, fixed by dfd01f0260
"sched/wait: Fix the signal handling fix"
Oleg.
On 04/12, Florian Fainelli wrote:
>
> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
>
> [ Upstream commit 68985633bccb6066bf1803e316fbc6c1f5b796d6 ]
>
> Vladimir reported getting RCU stall warnings and bisected it back to
> commit:
>
> 743162013d40 ("sched: Remove proliferation of wait_on_bit() action functions")
>
> That commit inadvertently reversed the calls to schedule() and signal_pending(),
> thereby not handling the case where the signal receives while we sleep.
>
> Reported-by: Vladimir Murzin <vladimir.murzin@xxxxxxx>
> Tested-by: Vladimir Murzin <vladimir.murzin@xxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Mike Galbraith <efault@xxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: mark.rutland@xxxxxxx
> Cc: neilb@xxxxxxx
> Cc: oleg@xxxxxxxxxx
> Fixes: 743162013d40 ("sched: Remove proliferation of wait_on_bit() action functions")
> Fixes: cbbce8220949 ("SCHED: add some "wait..on_bit...timeout()" interfaces.")
> Link: http://lkml.kernel.org/r/20151201130404.GL3816@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
> kernel/sched/wait.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
> index 852143a79f36..e0bb7e6c4fb0 100644
> --- a/kernel/sched/wait.c
> +++ b/kernel/sched/wait.c
> @@ -583,18 +583,18 @@ EXPORT_SYMBOL(wake_up_atomic_t);
>
> __sched int bit_wait(struct wait_bit_key *word)
> {
> - if (signal_pending_state(current->state, current))
> - return 1;
> schedule();
> + if (signal_pending(current))
> + return -EINTR;
> return 0;
> }
> EXPORT_SYMBOL(bit_wait);
>
> __sched int bit_wait_io(struct wait_bit_key *word)
> {
> - if (signal_pending_state(current->state, current))
> - return 1;
> io_schedule();
> + if (signal_pending(current))
> + return -EINTR;
> return 0;
> }
> EXPORT_SYMBOL(bit_wait_io);
> @@ -602,11 +602,11 @@ EXPORT_SYMBOL(bit_wait_io);
> __sched int bit_wait_timeout(struct wait_bit_key *word)
> {
> unsigned long now = ACCESS_ONCE(jiffies);
> - if (signal_pending_state(current->state, current))
> - return 1;
> if (time_after_eq(now, word->timeout))
> return -EAGAIN;
> schedule_timeout(word->timeout - now);
> + if (signal_pending(current))
> + return -EINTR;
> return 0;
> }
> EXPORT_SYMBOL_GPL(bit_wait_timeout);
> @@ -614,11 +614,11 @@ EXPORT_SYMBOL_GPL(bit_wait_timeout);
> __sched int bit_wait_io_timeout(struct wait_bit_key *word)
> {
> unsigned long now = ACCESS_ONCE(jiffies);
> - if (signal_pending_state(current->state, current))
> - return 1;
> if (time_after_eq(now, word->timeout))
> return -EAGAIN;
> io_schedule_timeout(word->timeout - now);
> + if (signal_pending(current))
> + return -EINTR;
> return 0;
> }
> EXPORT_SYMBOL_GPL(bit_wait_io_timeout);
> --
> 2.12.1
>