Aside of being conceptually wrong, there is also an actual (hard to
trigger and mostly theoretical) problem.
CPU0 CPU1
free_irq(X) interrupt X
spin_lock(desc->lock)
wake irq thread()
spin_unlock(desc->lock)
spin_lock(desc->lock)
remove action()
shutdown_irq()
release_resources() thread_handler()
spin_unlock(desc->lock) access released resources.
synchronize_irq()
Move the release resources invocation after synchronize_irq() so it's
guaranteed that the threaded handler has finished.
Move the resource request call out of the desc->lock held region as well,
so the invocation context is the same for both request and release.
This solves the problems with those functions on RT as well.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: Heiko Stuebner <heiko@sntech.de>
Cc: Julia Cartwright <julia@ni.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Brian Norris <briannorris@chromium.org>
Cc: Doug Anderson <dianders@chromium.org>
Cc: linux-rockchip@lists.infradead.org
Cc: John Keeping <john@metanate.com>
Cc: linux-gpio@vger.kernel.org
Link: http://lkml.kernel.org/r/20170629214344.117028181@linutronix.de
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