linux-kernel - Re: [PATCH v2 07/10] futex: use freezable blocking call

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Date:	Thu, 2 May 2013 21:45:56 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Colin Cross <ccross@...roid.com>
cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>, arve@...roid.com,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH v2 07/10] futex: use freezable blocking call

On Wed, 1 May 2013, Colin Cross wrote:

> Avoid waking up every thread sleeping in a futex_wait 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 call was selected to be converted to a freezable call because
> it doesn't hold any locks or release any resources when interrupted
> that might be needed by another freezing task or a kernel driver
> during suspend, and is a common site where idle userspace tasks are
> blocked.
> 
> Signed-off-by: Colin Cross <ccross@...roid.com>

Acked-by: Thomas Gleixner <tglx@...utronix.de>

> ---
>  kernel/futex.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/futex.c b/kernel/futex.c
> index b26dcfc..d710fae 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -61,6 +61,7 @@
>  #include <linux/nsproxy.h>
>  #include <linux/ptrace.h>
>  #include <linux/sched/rt.h>
> +#include <linux/freezer.h>
>  
>  #include <asm/futex.h>
>  
> @@ -1807,7 +1808,7 @@ static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
>  		 * is no timeout, or if it has yet to expire.
>  		 */
>  		if (!timeout || timeout->task)
> -			schedule();
> +			freezable_schedule();
>  	}
>  	__set_current_state(TASK_RUNNING);
>  }
> -- 
> 1.8.2.1
> 
> 
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