Re: [PATCH 3.14 40/98] clk: Really fix deadlock with mmap_sem

Luis Henriques
2015-01-26T12:46:21Z

On Sun, Jan 25, 2015 at 10:06:58AM -0800, Greg Kroah-Hartman wrote:
> 3.14-stable review patch. If anyone has any objections, please let me know.
>

This patch was tagged for stable 3.18 only. Also, since commit
6314b6796e3c doesn't seem to be in 3.14, I believe shouldn't be in
this stable kernel.

Cheers,
--
Luís

> ------------------
>
> From: Stephen Boyd <sboyd@codeaurora.org>
>
> commit 89f7e9de59bf3e3cda2e00de12c66db22675a7cf upstream.
>
> Commit 6314b6796e3c (clk: Don't hold prepare_lock across debugfs
> creation, 2014-09-04) forgot to update one place where we hold
> the prepare_lock while creating debugfs directories. This means
> we still have the chance of a deadlock that the commit was trying
> to fix. Actually fix it by moving the debugfs creation outside
> the prepare_lock.
>
> Reported-by: Russell King <rmk+kernel@arm.linux.org.uk>
> Fixes: 6314b6796e3c "clk: Don't hold prepare_lock across debugfs creation"
> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Michael Turquette <mturquette@linaro.org>
> [mturquette@linaro.org: removed lockdep_assert]
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> ---
> drivers/clk/clk.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -230,7 +230,6 @@ static const struct file_operations clk_
> .release = single_release,
> };
>
> -/* caller must hold prepare_lock */
> static int clk_debug_create_one(struct clk *clk, struct dentry *pdentry)
> {
> struct dentry *d;
> @@ -1902,7 +1901,6 @@ int __clk_init(struct device *dev, struc
> else
> clk->rate = 0;
>
> - clk_debug_register(clk);
> /*
> * walk the list of orphan clocks and reparent any that are children of
> * this clock
> @@ -1937,6 +1935,9 @@ int __clk_init(struct device *dev, struc
> out:
> clk_prepare_unlock();
>
> + if (!ret)
> + clk_debug_register(clk);
> +
> return ret;
> }
>
>
>
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