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

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Date:	Thu, 02 May 2013 20:12:58 -0700
From:	Darren Hart <dvhart@...ux.intel.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Colin Cross <ccross@...roid.com>, 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>,
	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 05/02/2013 12:45 PM, Thomas Gleixner wrote:
> 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>

Beat me to it :-) Also agreed.

Acked-by: Darren Hart <dvhart@...ux.intel.com>

> 
>> ---
>>  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
>>
>>

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Technical Lead - Linux Kernel
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