Quoting Sebastian Andrzej Siewior (2019-09-26 11:56:43) > The function intel_engine_breadcrumbs_irq() is always invoked from an interrupt > handler and for that reason it invokes (as an optimisation) only spin_lock() > for locking assuming that the interrupts are already disabled. The > function intel_engine_signal_breadcrumbs() is provided to disable > interrupts while the former function is invoked so that assumption is > also true for callers from preemptible context. > > On PREEMPT_RT local_irq_disable() really disables interrupts and this > forbids to invoke spin_lock() which becomes a sleeping spinlock. > > This is also problematic with `threadirqs' in conjunction with > irq_work. With force threading the interrupt handler, the handler is > invoked with disabled BH but with interrupts enabled. This is okay and > the lock itself is never acquired in IRQ context. This changes with > irq_work (signal_irq_work()) which _still_ invokes > intel_engine_breadcrumbs_irq() from IRQ context. Lockdep should see this > and complain. > > Acquire the locks in intel_engine_breadcrumbs_irq() with _irqsave() > suffix and let all callers invoke intel_engine_breadcrumbs_irq() > directly instead using intel_engine_signal_breadcrumbs(). > > Reported-by: Clark Williams <williams@xxxxxxxxxx> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> All those irq save/restore look annoying, still the argument is valid Reviewed: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> -Chris _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
