linux-kernel - Re: [PATCH v4 1/9] clkdev: Hold clocks

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Message-ID: <20190415052214.GA31948@localhost.localdomain>
Date:   Mon, 15 Apr 2019 08:22:14 +0300
From:   Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Russell King <linux@...linux.org.uk>,
        Jeffrey Hugo <jhugo@...eaurora.org>,
        Chen-Yu Tsai <wens@...e.org>
Subject: Re: [PATCH v4 1/9] clkdev: Hold clocks_mutex while iterating clocks
 list

On Fri, Apr 12, 2019 at 11:31:42AM -0700, Stephen Boyd wrote:
> We recently introduced a change to support devm clk lookups. That change
> introduced a code-path that used clk_find() without holding the
> 'clocks_mutex'. Unfortunately, clk_find() iterates over the 'clocks'
> list and so we need to prevent the list from being modified at the same
> time. Do this by holding the mutex and checking to make sure it's held
> while iterating the list.
> 
> Note, we don't really care if the lookup is freed after we find it with
> clk_find() because we're just doing a pointer comparison, but if we did
> care we would need to keep holding the mutex while we dereference the
> clk_lookup pointer.
> 
> Fixes: 3eee6c7d119c ("clkdev: add managed clkdev lookup registration")
> Cc: Miquel Raynal <miquel.raynal@...tlin.com>
> Cc: Jerome Brunet <jbrunet@...libre.com>
> Cc: Russell King <linux@...linux.org.uk>
> Cc: Michael Turquette <mturquette@...libre.com>
> Cc: Jeffrey Hugo <jhugo@...eaurora.org>
> Cc: Chen-Yu Tsai <wens@...e.org>
> Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
> Signed-off-by: Stephen Boyd <sboyd@...nel.org>
Acked-By: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>