linux-kernel - Re: [PATCH] usb: musb: Fix runtime PM race in musb_queue_resume

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Date:   Mon, 17 Aug 2020 13:59:26 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Bin Liu <b-liu@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Johan Hovold <johan@...nel.org>, od@...c.me,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] usb: musb: Fix runtime PM race in musb_queue_resume_work

* Paul Cercueil <paul@...pouillou.net> [200809 12:54]:
> musb_queue_resume_work() would call the provided callback if the runtime
> PM status was 'active'. Otherwise, it would enqueue the request if the
> hardware was still suspended (musb->is_runtime_suspended is true).
> 
> This causes a race with the runtime PM handlers, as it is possible to be
> in the case where the runtime PM status is not yet 'active', but the
> hardware has been awaken (PM resume function has been called).
> 
> When hitting the race, the resume work was not enqueued, which probably
> triggered other bugs further down the stack. For instance, a telnet
> connection on Ingenic SoCs would result in a 50/50 chance of a
> segmentation fault somewhere in the musb code.
> 
> Rework the code so that either we call the callback directly if
> (musb->is_runtime_suspended == 0), or enqueue the query otherwise.

Yes we should use is_runtime_suspended, thanks for fixing it.
Things still work for me so:

Reviewed-by: Tony Lindgren <tony@...mide.com>
Tested-by: Tony Lindgren <tony@...mide.com>