From: Wolfram Sang <wsa@kernel.org>
To: "Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>
Cc: John Stultz <john.stultz@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Stephen Boyd <sboyd@kernel.org>,
linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org
Subject: Re: [PATCH v2] timekeeping: Allow runtime PM from change_clocksource()
Date: Wed, 3 Mar 2021 12:04:13 +0100 [thread overview]
Message-ID: <20210303110413.GB3689@kunai> (raw)
In-Reply-To: <20210211134318.323910-1-niklas.soderlund+renesas@ragnatech.se>
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On Thu, Feb 11, 2021 at 02:43:18PM +0100, Niklas Söderlund wrote:
> The struct clocksource callbacks enable() and disable() are described as
> a way to allow clock sources to enter a power save mode [1]. But using
> runtime PM from these callbacks triggers a cyclic lockdep warning when
> switching clock source using change_clocksource().
>
> This change allows the new clocksource to be enabled() and the old one
> to be disabled() without holding the timekeeper_lock. This solution is
> modeled on timekeeping_resume() and timekeeping_suspend() where the
> struct clocksource resume() and suspend() callbacks are called without
> holding the timekeeper_lock.
>
> Triggering and log of the deadlock warning,
>
> # echo e60f0000.timer > /sys/devices/system/clocksource/clocksource0/current_clocksource
...
I had the same issue when running 'clocksource-switch' from the Kernel
selftests with a Renesas Falcon board using a R-Car V3U. This patch
fixed the deadlock warning, so:
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
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next prev parent reply other threads:[~2021-03-03 16:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-11 13:43 Niklas Söderlund
2021-03-03 11:04 ` Wolfram Sang [this message]
2021-03-29 14:47 ` [tip: timers/core] " tip-bot2 for Niklas Söderlund
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