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0263f92f |
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20-Nov-2023 |
Ming Lei <ming.lei@redhat.com> |
lib/group_cpus.c: avoid acquiring cpu hotplug lock in group_cpus_evenly group_cpus_evenly() could be part of storage driver's error handler, such as nvme driver, when may happen during CPU hotplug, in which storage queue has to drain its pending IOs because all CPUs associated with the queue are offline and the queue is becoming inactive. And handling IO needs error handler to provide forward progress. Then deadlock is caused: 1) inside CPU hotplug handler, CPU hotplug lock is held, and blk-mq's handler is waiting for inflight IO 2) error handler is waiting for CPU hotplug lock 3) inflight IO can't be completed in blk-mq's CPU hotplug handler because error handling can't provide forward progress. Solve the deadlock by not holding CPU hotplug lock in group_cpus_evenly(), in which two stage spreads are taken: 1) the 1st stage is over all present CPUs; 2) the end stage is over all other CPUs. Turns out the two stage spread just needs consistent 'cpu_present_mask', and remove the CPU hotplug lock by storing it into one local cache. This way doesn't change correctness, because all CPUs are still covered. Link: https://lkml.kernel.org/r/20231120083559.285174-1-ming.lei@redhat.com Signed-off-by: Ming Lei <ming.lei@redhat.com> Reported-by: Yi Zhang <yi.zhang@redhat.com> Reported-by: Guangwu Zhang <guazhang@redhat.com> Tested-by: Guangwu Zhang <guazhang@redhat.com> Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com> Reviewed-by: Jens Axboe <axboe@kernel.dk> Cc: Keith Busch <kbusch@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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f7b3ea8c |
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26-Dec-2022 |
Ming Lei <ming.lei@redhat.com> |
genirq/affinity: Move group_cpus_evenly() into lib/ group_cpus_evenly() has become a generic function which can be used for other subsystems than the interrupt subsystem, so move it into lib/. Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Jens Axboe <axboe@kernel.dk> Link: https://lore.kernel.org/r/20221227022905.352674-6-ming.lei@redhat.com
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