On Wed, Aug 19, 2020 at 02:34:16PM +0100, Alexandru Elisei wrote: > From: Julien Thierry <julien.thie...@arm.com> > > When handling events, armv8pmu_handle_irq() calls perf_event_overflow(), > and subsequently calls irq_work_run() to handle any work queued by > perf_event_overflow(). As perf_event_overflow() raises IPI_IRQ_WORK when > queuing the work, this isn't strictly necessary and the work could be > handled as part of the IPI_IRQ_WORK handler. > > In the common case the IPI handler will run immediately after the PMU IRQ > handler, and where the PE is heavily loaded with interrupts other handlers > may run first, widening the window where some counters are disabled. > > In practice this window is unlikely to be a significant issue, and removing > the call to irq_work_run() would make the PMU IRQ handler NMI safe in > addition to making it simpler, so let's do that.
Makes sense, IIRC this code was written before ARM grew IPI_IRQ_WORK support and then it makes sense, but now that you have it and are moving to NMI-like context this is absolutely the right thing to do.
