linux-kernel - Re: restart_syscall: use freezable blocking call

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Message-ID: <1982905.Ac4fTCSUaY@vostro.rjw.lan>
Date:	Tue, 31 Mar 2015 01:39:07 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, maninder1.s@...sung.com,
	tglx@...utronix.de, Yogesh Narayan Gaur <yn.gaur@...sung.com>,
	AJEET YADAV <ajeet.y@...sung.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Tejun Heo <tj@...nel.org>
Subject: Re: restart_syscall: use freezable blocking call

CC more maintainers.

On Monday, March 30, 2015 03:43:51 PM Andrew Morton wrote:
> On Mon, 30 Mar 2015 11:07:35 +0000 (GMT) Maninder Singh <maninder1.s@...sung.com> 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@...sung.com>
> 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@...utronix.de>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
> 
>  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);
> _
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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