linux-kernel - Re: When it is save to kfree() hrtimer object?

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Message-ID: <alpine.LFD.2.00.0912071127440.3089@localhost.localdomain>
Date:	Mon, 7 Dec 2009 11:35:31 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"Nikita V. Youshchenko" <yoush@...msu.su>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: When it is save to kfree() hrtimer object?

On Mon, 7 Dec 2009, Nikita V. Youshchenko wrote:
> - Isn't it a bug that timer object is accessed after it's callback was 
> called and returned HRTIMER_NORESTART?

No, it's not. It's deliberately implemented that way.

> - If that is not a bug, then when it is "officially safe" to deallocate 
> struct hrtimer object?

When it's neither enqueued nor running the callback. See the other use
sites.
 
> - Are there any recommendations on how to implement "single-shot" timers 
> like in my case?

Well, you wake up something which waits on completion of that request,
right ? Probably the caller which issued the request. Why don't you
free the request in the waiter context after it got woken up ?

Thanks,

	tglx
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