From mboxrd@z Thu Jan  1 00:00:00 1970
From: Kevin Hilman <khilman@baylibre.com>
Subject: Re: [PATCH] PM / Domains: Restore lock-less behaviour for the genpd syscore APIs
Date: Tue, 07 Feb 2017 10:29:02 -0800
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References: <1486482784-31734-1-git-send-email-ulf.hansson@linaro.org>
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In-Reply-To: <1486482784-31734-1-git-send-email-ulf.hansson@linaro.org> (Ulf
        Hansson's message of "Tue, 7 Feb 2017 16:53:04 +0100")
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To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>, linux-pm@vger.kernel.org, Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>, Geert Uytterhoeven <geert@linux-m68k.org>, Lina Iyer <lina.iyer@linaro.org>, Jon Hunter <jonathanh@nvidia.com>, Marek Szyprowski <m.szyprowski@samsung.com>, Brian Norris <briannorris@chromium.org>

Ulf Hansson <ulf.hansson@linaro.org> writes:

> The commit ef4f7e2c8335 ("PM / Domains: Fix asynchronous execution of
> *noirq() callbacks") went too far, as it not only changed to use locks for
> the *noirq callbacks, but also for the genpd syscore APIs.
>
> This cause the following error, reported by Geert Uytterhoeven:
>
> "This causes the following BUG on all my Renesas arm32 boards, where the
> system timer is an IRQ safe device:
>
> BUG: sleeping function called from invalid context at
> kernel/locking/mutex.c:232
> in_atomic(): 0, irqs_disabled(): 128, pid: 1751, name: s2ram
> CPU: 0 PID: 1751 Comm: s2ram Not tainted
> 4.10.0-rc7-koelsch-05643-g27f4c73972a614fe #3354
> Hardware name: Generic R8A7791 (Flattened Device Tree)
> [<c020e9c4>] (unwind_backtrace) from [<c020a40c>] (show_stack+0x10/0x14)
> [<c020a40c>] (show_stack) from [<c03f9818>] (dump_stack+0x7c/0x9c)
> [<c03f9818>] (dump_stack) from [<c0240020>] (___might_sleep+0x124/0x160)
> [<c0240020>] (___might_sleep) from [<c06fedfc>] (mutex_lock+0x18/0x60)
> [<c06fedfc>] (mutex_lock) from [<c04de340>]
> (genpd_syscore_switch+0x2c/0x7c)
> [<c04de340>] (genpd_syscore_switch) from [<c05ec328>]
> (sh_cmt_clock_event_suspend+0x18/0x28)
> [<c05ec328>] (sh_cmt_clock_event_suspend) from [<c027f9a4>]
> (clockevents_suspend+0x40/0x54)
> [<c027f9a4>] (clockevents_suspend) from [<c0276d48>]
> (timekeeping_suspend+0x23c/0x278)
> [<c0276d48>] (timekeeping_suspend) from [<c04cbb88>]
> (syscore_suspend+0x88/0x138)
> [<c04cbb88>] (syscore_suspend) from [<c025f618>]
> (suspend_devices_and_enter+0x290/0x470)
> [<c025f618>] (suspend_devices_and_enter) from [<c025fa20>]
> (pm_suspend+0x228/0x280)
> [<c025fa20>] (pm_suspend) from [<c025e60c>] (state_store+0xac/0xcc)
> [<c025e60c>] (state_store) from [<c0340c4c>] (kernfs_fop_write+0x160/0x19c)
> [<c0340c4c>] (kernfs_fop_write) from [<c02e3054>] (__vfs_write+0x20/0x108)
> [<c02e3054>] (__vfs_write) from [<c02e4424>] (vfs_write+0xb8/0x144)
> [<c02e4424>] (vfs_write) from [<c02e5014>] (SyS_write+0x40/0x80)
> [<c02e5014>] (SyS_write) from [<c0206cc0>] (ret_fast_syscall+0x0/0x34)"
>
> To fix this problem, restore the lock-less behaviour. However only for the
> genpd syscore APIs.
>
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Fixes: ef4f7e2c8335 ("PM / Domains: Fix asynchronous execution of *noirq() callbacks")
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

It's up to Rafael, but IMO, since this isn't yet in mainline, it would
be cleaner for the git history to revert the original, and rework the
patch to have just the relevant parts

Kevin