linux-kernel - Re: [PATCH 4/5] clk: Get runtime PM before walking tree during disable

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Date: Mon, 25 Mar 2024 10:15:50 -0700
From: Doug Anderson <dianders@...omium.org>
To: Stephen Boyd <sboyd@...nel.org>
Cc: Michael Turquette <mturquette@...libre.com>, linux-kernel@...r.kernel.org, 
	linux-clk@...r.kernel.org, patches@...ts.linux.dev, 
	linux-arm-msm@...r.kernel.org, Marek Szyprowski <m.szyprowski@...sung.com>, 
	Ulf Hansson <ulf.hansson@...aro.org>, Krzysztof Kozlowski <krzk@...nel.org>
Subject: Re: [PATCH 4/5] clk: Get runtime PM before walking tree during disable_unused

Hi,

On Mon, Mar 25, 2024 at 10:06 AM Stephen Boyd <sboyd@...nel.org> wrote:
>
> > > +/*
> > > + * Call clk_pm_runtime_get() on all runtime PM enabled clks in the clk tree so
> > > + * that disabling unused clks avoids a deadlock where a device is runtime PM
> > > + * resuming/suspending and the runtime PM callback is trying to grab the
> > > + * prepare_lock for something like clk_prepare_enable() while
> > > + * clk_disable_unused_subtree() holds the prepare_lock and is trying to runtime
> > > + * PM resume/suspend the device as well.
> > > + */
> > > +static int clk_pm_runtime_get_all(void)
> >
> > nit: It'd be nice if this documented that it acquired / held the lock.
> > Could be in comments, or, might as well use the syntax like this (I
> > think):
> >
> > __acquires(&clk_rpm_list_lock);
> >
> > ...similar with the put function.
>
> I had that but removed it because on the error path we drop the lock and
> sparse complains. I don't know how to signal that the lock is held
> unless an error happens, but I'm a little out of date on sparse now.

I'd settle for something in the comments then? Maybe tagged with "Context:" ?

Thanks!

-Doug