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

[Luis Henriques]

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@xxxxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxxxxxx>
> Fixes: 6314b6796e3c "clk: Don't hold prepare_lock across debugfs creation"
> Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
> Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Signed-off-by: Michael Turquette <mturquette@xxxxxxxxxx>
> [mturquette@xxxxxxxxxx: removed lockdep_assert]
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> 
> ---
>  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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