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Date:   Thu, 16 Jun 2022 08:17:13 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Adrien Thierry <athierry@redhat.com>
Cc:     linux-rt-users@vger.kernel.org,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Kevin Hilman <khilman@kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
        Andrew Halaney <ahalaney@redhat.com>,
        Eric Chanudet <echanude@redhat.com>,
        Brian Masney <bmasney@redhat.com>, linux-pm@vger.kernel.org
Subject: Re: [PATCH RFC] base: power: replace generic_pm_domain spinlock by
 raw spinlock
Message-ID: <YqrK6RZes4W4bZJd@kroah.com>
References: <20220615203605.1068453-1-athierry@redhat.com>
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On Wed, Jun 15, 2022 at 04:36:05PM -0400, Adrien Thierry wrote:
> We've been encountering a BUG: scheduling while atomic while running the
> 5.18.0-rt11 kernel on a Qualcomm SoC (see stacktrace below).
> 
> It seems to occur because a spinlock is taken in the PSCI idle code path
> in the idle loop. With the RT patchset applied and CONFIG_PREEMPT_RT
> enabled, spinlocks can sleep, thus triggering the bug.
> 
> In order to prevent this, replace the generic_pm_domain spinlock by a
> raw spinlock.

Ick.  I'll leave this to the RT people, but having a spinlock sleep
feels totally wrong overall and I didn't think that was something that
actually happened.

For mainline, I don't think this is a valid change at this point in time
untill you all work out the details more.

thanks,

greg k-h