linux-kernel - Re: [PATCH] PM / OPP: Protect updates to list

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Date:	Wed, 4 Nov 2015 14:11:25 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	Rafael Wysocki <rjw@...ysocki.net>, mturquette@...libre.com,
	linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Dmitry Torokhov <dtor@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Len Brown <len.brown@...el.com>,
	open list <linux-kernel@...r.kernel.org>,
	Nishanth Menon <nm@...com>, Pavel Machek <pavel@....cz>
Subject: Re: [PATCH] PM / OPP: Protect updates to list_dev with mutex

On 10/30, Viresh Kumar wrote:
> dev_opp_list_lock is used everywhere to protect device and OPP lists,
> but dev_pm_opp_set_sharing_cpus() is missed somehow. And instead we used
> rcu-lock, which wouldn't help here as we are adding a new list_dev.
> 
> This also fixes a problem where we have called kzalloc(..., GFP_KERNEL)
> from within rcu-lock, which isn't allowed as kzalloc can sleep when
> called with GFP_KERNEL.
> 
> With CONFIG_DEBUG_ATOMIC_SLEEP set, we will see the caller vomiting.
> 
> Fixes: 8d4d4e98acd6 ("PM / OPP: Add helpers for initializing CPU OPPs")
> Reported-by: Michael Turquette <mturquette@...libre.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---

Reviewed-by: Stephen Boyd <sboyd@...eaurora.org>

I assume some other patch will come to fix the comment and/or add
the lockdep check.

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