linux-kernel - Re: [PATCH] sky2: Use deferrable timer for watchdog

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Message-ID: <82e4877d0712201005u3e1abd4t675b3b0f21b8ff4c@mail.gmail.com>
Date:	Thu, 20 Dec 2007 13:05:58 -0500
From:	"Parag Warudkar" <parag.warudkar@...il.com>
To:	"Stephen Hemminger" <shemminger@...ux-foundation.org>
Cc:	netdev@...r.kernel.org, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sky2: Use deferrable timer for watchdog

On Dec 20, 2007 12:51 PM, Stephen Hemminger
<shemminger@...ux-foundation.org> wrote:
>
> Quit top-posting!
>
> If this is the case then the whole usage of round_jiffies() is bogus. All users of round_jiffies()
> should just be converted to deferrable??  I am a bit concerned that if deferrable gets used everywhere
> then a strange situation would occur where all timers were waiting for some other timer to finally
> happen, kind of a wierd timelock situation. Like the old chip/dale cartoon:
>  "you first, no you first, after you mister chip, no after you mister dale,..."
>

Haha - I thought about this too. I think there should be mechanism
where the machine does not idle infinitely even if there are no
non-deferrable timers. Something like an affordable QoS for non
deferrable timers - the kernel wakes up after that interval and runs
all deferrable timers  even if nothing non-deferrable is set to run.
So we still get advantage of not having to wake individually for each
timer and the non-deferrable timers do get all run in reasonable
amount of time.

Who knows Thomas/Ingo already built in something of that nature or effect?!

Parag
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