linux-kernel - Re: [PATCH] PM: add: move warn message out of mutex lock.

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Message-ID: <CAJZ5v0itLuorOY-4PyDL5eFkWTf2s9JX++oBkzqi1cYcaHYdmA@mail.gmail.com>
Date: Tue, 3 Sep 2024 16:10:16 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: David Wang <00107082@....com>
Cc: len.brown@...el.com, pavel@....cz, gregkh@...uxfoundation.org, 
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PM: add: move warn message out of mutex lock.

On Tue, Sep 3, 2024 at 3:01 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Mon, Sep 2, 2024 at 7:50 AM David Wang <00107082@....com> wrote:
> >
> > dpm_list_mtx does not protect any data used by
> > dev_warn for checking parent's power, move
> > dev_warn out of mutex lock block make the
> > lock more efficient, especially when the warn
> > is triggered.
>
> It does protect the power.is_prepared flag of the parent.

In fact, the update of it in device_resume() is racy with respect to
the check in device_pm_add(), but the purpose of it is mostly to allow
the device driver's resume callback to add children without triggering
the warning.