linux-kernel - Re: Synchronization mechanism between wait_for_completion_interruptible

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Message-ID: <20150305132306.GA19664@dhcp22.suse.cz>
Date:	Thu, 5 Mar 2015 14:23:06 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Naveen Kumar Parna <pnaveenkos@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Synchronization mechanism between
 wait_for_completion_interruptible_timeout() & complete()

On Wed 04-03-15 18:46:43, Naveen Kumar Parna wrote:
> Hello,
> 
> I have a question regarding the synchronization mechanism between
> wait_for_completion_interruptible_timeout() & complete(). I used
> complete() API in the ISR Tx interrupt path and
> wait_for_completion_interruptible_timeout() in struct file_operations
> .write method.
> 
> Let assume a scenario in which Tx interrupt occurred and ISR called
> complete() API before any process actually blocked at write method on
> wait_for_completion_interruptible_timeout().
> 
> After a few milli seconds, a process called write() API. Does it gets
> blocked on wait_for_completion_interruptible_timeout() for completion
> of a specific task to be signaled from new Tx interrupt?

No, see do_wait_for_common resp. complete and x->done handling.

-- 
Michal Hocko
SUSE Labs
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