Re: restart_syscall: use freezable blocking call

[Andrew Morton]

On Mon, 30 Mar 2015 11:07:35 +0000 (GMT) Maninder Singh <maninder1.s@xxxxxxxxxxx> wrote:

> Hello All, 
> 
> Avoid waking up every thread sleeping in a restart_syscall call during suspend and resume by calling a freezable blocking call. 
> Previous patches modified the freezer to avoid sending wakeups to threads that are blocked in freezable blocking calls.
> Ref: https://lkml.org/lkml/2013/5/1/424
> We have faced similiar issue of sleep fail when calling restart() system call in stress testing.
> 
> Patch :-
> Subject: restart_syscall: use freezable blocking call
> Avoid waking up every thread sleeping in a restart_syscall call during
> suspend and resume by calling a freezable blocking call.  Previous
> patches modified the freezer to avoid sending wakeups to threads
> that are blocked in freezable blocking calls.

This patch is rather mucked up - tabs replaced with spaces, apparently
mangled text in the changelog.

Thomas is having a bit of time off, so I fixed most of that up and
queued the patch in -mm for some testing.  Hopefully Thomas and/or
Rafael will be able to comment?


From: Maninder Singh <maninder1.s@xxxxxxxxxxx>
Subject: kernel/time/hrtimer.c: restart_syscall: use freezable blocking call

Avoid waking up every thread sleeping in a restart_syscall call during
suspend and resume by calling a freezable blocking call.  Previous patches
modified the freezer to avoid sending wakeups to threads that are blocked
in freezable blocking calls.

Ref: https://lkml.org/lkml/2013/5/1/424

Backtrace: 
[<c03e3924>] (__schedule+0x0/0x5d8) from [<c03e3f88>] (schedule+0x8c/0x90)
[<c03e3efc>] (schedule+0x0/0x90) from [<c03e3150>] (schedule_hrtimeout_range_clock+0xdc/0x110)
[<c03e3074>] (schedule_hrtimeout_range_clock+0x0/0x110) from [<c03e31a0>] (schedule_hrtimeout_range+0x1c/0x20)
 r9:d16c9be0 r8:8b7d9c2c r7:00000000 r6:00000000 r5:d16c8028
[<c03e3184>] (schedule_hrtimeout_range+0x0/0x20) from [<c015778c>] (poll_schedule_timeout+0x48/0x6c)
[<c0157744>] (poll_schedule_timeout+0x0/0x6c) from [<c0158994>] (do_sys_poll+0x2c8/0x378) r5:d16c9f78 r4:00000000
[<c01586cc>] (do_sys_poll+0x0/0x378) from [<c0158a84>] (do_restart_poll+0x40/0x5c)
[<c0158a44>] (do_restart_poll+0x0/0x5c) from [<c005710c>] (sys_restart_syscall+0x2c/0x30) r4:fffffe7a
[<c00570e0>] (sys_restart_syscall+0x0/0x30) from [<c001a180>] (ret_fast_syscall+0x0/0x48)


Signed-off-by: Yogesh Gaur <yn.gaur <at> samsung.com>
Signed-off-by: Amit Arora <amit.arora <at> samsung.com>
Reviewed-by : Ajeet Yadav <ajeet.y <at> samsung.com>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 kernel/time/hrtimer.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff -puN kernel/time/hrtimer.c~restart_syscall-use-freezable-blocking-call kernel/time/hrtimer.c
--- a/kernel/time/hrtimer.c~restart_syscall-use-freezable-blocking-call
+++ a/kernel/time/hrtimer.c
@@ -1767,7 +1767,7 @@ schedule_hrtimeout_range_clock(ktime_t *
 	 * A NULL parameter means "infinite"
 	 */
 	if (!expires) {
-		schedule();
+		freezable_schedule();
 		return -EINTR;
 	}
 
@@ -1781,7 +1781,7 @@ schedule_hrtimeout_range_clock(ktime_t *
 		t.task = NULL;
 
 	if (likely(t.task))
-		schedule();
+		freezable_schedule();
 
 	hrtimer_cancel(&t.timer);
 	destroy_hrtimer_on_stack(&t.timer);
_

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