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Date: Tue, 10 Aug 2021 22:33:01 +0200 From: Thomas Gleixner <tglx@...utronix.de> To: Valentin Schneider <valentin.schneider@....com>, linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org Cc: Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>, Marc Zyngier <maz@...nel.org>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Mel Gorman <mgorman@...hsingularity.net>, Linus Walleij <linusw@...nel.org>, Bartosz Golaszewski <bgolaszewski@...libre.com>, linux-gpio@...r.kernel.org Subject: Re: [SPLAT 3/3] gpio: dwapb: Sleeping spinlocks down IRQ mapping On Tue, Aug 10 2021 at 14:41, Valentin Schneider wrote: > [ 11.549824] rt_spin_lock (kernel/locking/rtmutex.c:1641 (discriminator 4) kernel/locking/spinlock_rt.c:30 (discriminator 4) kernel/locking/spinlock_rt.c:36 (discriminator 4) kernel/locking/spinlock_rt.c:44 (discriminator 4)) > [ 11.549827] dwapb_irq_ack (drivers/gpio/gpio-dwapb.c:151 drivers/gpio/gpio-dwapb.c:233) gpio_dwapb > [ 11.549831] __irq_do_set_handler (kernel/irq/chip.c:414 kernel/irq/chip.c:406 kernel/irq/chip.c:1009) > [ 11.549833] __irq_set_handler (kernel/irq/internals.h:178 kernel/irq/chip.c:1053) This is gpio_chip->bgpio_lock which is a regular spinlock. AFAICT this lock should merely serializing access to MMIO registers, so it should not be a problem to make this lock raw. Except for the obligatory exception: grgpio_irq_handler() holds that lock from the demultiplexing handler and invokes all handlers for the individual GPIOs which have interrupts enabled without ever consulting a pending register. That drivers usage of that lock is interesting in general, see grgpio_map_irq() for illustration. Quality stuff for mission critical systems... But nevertheless it should just work with a raw lock on RT AFACIT. Thanks, tglx
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