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

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Date:	Mon, 29 Apr 2013 15:52:27 -0700
From:	Darren Hart <dvhart@...ux.intel.com>
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,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Matthew Helsley <matthltc@...ibm.com>
Subject: Re: [PATCH 07/10] futex: use freezable blocking call

Colin,

I don't know anything about when or when not to use freezable*, and I
suspect that may be true for others as well. A more complete
description of why it's acceptable here in the commit log might help
expedite acceptance.


Matt,

I have a vague memory of discussing something similar to this with you.
Do you see any potential problems here?

--
Darren

On 04/29/2013 02:45 PM, Colin Cross wrote:
> Avoid waking up every thread sleeping in a futex_wait call during
> suspend and resume by calling a freezable blocking call.
> 
> Signed-off-by: Colin Cross <ccross@...roid.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);
>  }
> 

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