linux-kernel - Re: [RFC PATCH] hrtimer: removing all ur callback modes

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Date:	Sun, 07 Dec 2008 12:22:19 +0100
From:	Oliver Hartkopp <oliver@...tkopp.net>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC PATCH] hrtimer: removing all ur callback modes

Peter Zijlstra wrote:
> On Tue, 2008-11-25 at 12:43 +0100, Peter Zijlstra wrote:
>   
>> Hi,
>>
>> This is an attempt at removing some of the hrtimer complexity by
>> reducing the number of callback modes to 1.
>>
>> This means that all hrtimer callback functions will be ran from HARD-irq
>> context.
>>
>> I went through all the 30 odd hrtimer callback functions in the kernel
>> and saw only one that I'm not quite sure of, which is the one in
>> net/can/bcm.c - hence I'm CC-ing the folks responsible for that code.
>>     

Thanks Peter.

Indeed i assumed my hrtimer callbacks to run in soft-irq. I tried the 
can-bcm protocol with Ingos current linux-2.6-sched-devel.git including 
your patches and i did not see any issues so far. And i do not expect 
any (recursion) problems with hrtimer_forward() in my code either.

But i'm not that familiar with the timer context's stuff, that i would 
like guaranty that the functions i use in bcm_send_user() and in 
bcm_can_tx() are always safe to be used in hard-irq context.

It would be nice, if you could give me some support by double checking 
the correctness of the hard-irq context in the given functions.

Best regards,
Oliver

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