linux-kernel - Re: [PATCH] arm: sched: stop sched

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Date:	Tue, 23 Oct 2012 12:11:21 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Felipe Balbi <balbi@...com>
Cc:	Russell King <rmk+kernel@....linux.org.uk>,
	Linux ARM Kernel Mailing List 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kevin Hilman <khilman@...com>, Paul Walmsley <paul@...an.com>,
	Tony Lindgren <tony@...mide.com>,
	Santosh Shilimkar <santosh.shilimkar@...com>
Subject: Re: [PATCH] arm: sched: stop sched_clock() during suspend

On Mon, Oct 22, 2012 at 1:54 PM, Felipe Balbi <balbi@...com> wrote:

> The scheduler imposes a requirement to sched_clock()
> which is to stop the clock during suspend, if we don't
> do that IRQ threads will be rescheduled in the future
> which might cause transfers to timeout depending on
> how driver is written.
>
> This became an issue on OMAP when we converted omap-i2c.c
> to use threaded IRQs, it turned out that depending on how
> much time we spent on suspend, the I2C IRQ thread would
> end up being rescheduled so far in the future that I2C
> transfers would timeout and, because omap_hsmmc depends
> on an I2C-connected device to detect if an MMC card is
> inserted in the slot, our rootfs would just vanish.
>
> arch/arm/kernel/sched_clock.c already had an optional
> implementation (sched_clock_needs_suspend()) which would
> handle scheduler's requirement properly, what this patch
> does is simply to make that implementation non-optional.
>
> This has been tested with beagleboard XM (OMAP3630) and
> pandaboard rev A3 (OMAP4430). Suspend to RAM is now working
> after this patch.
>
> Signed-off-by: Felipe Balbi <balbi@...com>

After Russell explains so I get it:
Acked-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij
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