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From: Guenter Roeck <linux@roeck-us.net>
To: Doug Anderson <dianders@chromium.org>, wim@iguana.be
Cc: jszhang@marvell.com, Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] watchdog: dw_wdt: No need for a spinlock
Date: Thu, 07 May 2015 21:51:03 -0700	[thread overview]
Message-ID: <554C40B7.9060806@roeck-us.net> (raw)
In-Reply-To: <1431059265-9204-1-git-send-email-dianders@chromium.org>

On 05/07/2015 09:27 PM, Doug Anderson wrote:
> Right now the dw_wdt uses a spinlock to protect dw_wdt_open().  The
> problem is that while holding the spinlock we call:
> -> dw_wdt_set_top()
>     -> dw_wdt_top_in_seconds()
>        -> clk_get_rate()
>           -> clk_prepare_lock()
>              -> mutex_lock()
>
> Locking a mutex while holding a spinlock is not allowed and leads to
> warnings like "BUG: spinlock wrong CPU on CPU#1", among other
> problems.
>
> There's no reason to use a spinlock.  Only dw_wdt_open() was protected
> and the test_and_set_bit() at the start of that function protects us
> anyway.
>
> Signed-off-by: Doug Anderson <dianders@chromium.org>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>


  parent reply	other threads:[~2015-05-08  4:51 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-08  4:27 [PATCH v2 1/2] watchdog: dw_wdt: No need for a spinlock Doug Anderson
2015-05-08  4:27 ` [PATCH v2 2/2] watchdog: dw_wdt: keepalive the watchdog at write time Doug Anderson
2015-05-08  5:24   ` Dmitry Torokhov
2015-05-08  4:51 ` Guenter Roeck [this message]
2015-05-08  5:01 ` [PATCH v2 1/2] watchdog: dw_wdt: No need for a spinlock Jisheng Zhang
2015-05-08  5:23 ` Dmitry Torokhov

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