| Message ID | YrLSEiNvagKJaDs5@linutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] blk-mq: Don't disable preemption around __blk_mq_run_hw_queue(). | expand |
On Wed, Jun 22, 2022 at 10:25:54AM +0200, Sebastian Andrzej Siewior wrote: > __blk_mq_delay_run_hw_queue() disables preemption to get a stable > current CPU number and then invokes __blk_mq_run_hw_queue() if the CPU > number is part the mask. > > __blk_mq_run_hw_queue() acquires a spin_lock_t which is a sleeping lock > on PREEMPT_RT and can't be acquired with disabled preemption. > > It is not required for correctness to invoke __blk_mq_run_hw_queue() on > a CPU matching hctx->cpumask. Both (async and direct requests) can run > on a CPU not matching hctx->cpumask. > > The CPU mask without disabling preemption and invoking > __blk_mq_run_hw_queue(). > > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Looks fine: Reviewed-by: Ming Lei <ming.lei@redhat.com> Thanks, Ming
On Wed, 22 Jun 2022 10:25:54 +0200, Sebastian Andrzej Siewior wrote: > __blk_mq_delay_run_hw_queue() disables preemption to get a stable > current CPU number and then invokes __blk_mq_run_hw_queue() if the CPU > number is part the mask. > > __blk_mq_run_hw_queue() acquires a spin_lock_t which is a sleeping lock > on PREEMPT_RT and can't be acquired with disabled preemption. > > [...] Applied, thanks! [1/1] blk-mq: Don't disable preemption around __blk_mq_run_hw_queue(). commit: c9198d784fa93d447afe8e4627dfe205f0ce5ec8 Best regards,
--- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2085,14 +2085,10 @@ static void __blk_mq_delay_run_hw_queue( return; if (!async && !(hctx->flags & BLK_MQ_F_BLOCKING)) { - int cpu = get_cpu(); - if (cpumask_test_cpu(cpu, hctx->cpumask)) { + if (cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask)) { __blk_mq_run_hw_queue(hctx); - put_cpu(); return; } - - put_cpu(); } kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work,
__blk_mq_delay_run_hw_queue() disables preemption to get a stable current CPU number and then invokes __blk_mq_run_hw_queue() if the CPU number is part the mask. __blk_mq_run_hw_queue() acquires a spin_lock_t which is a sleeping lock on PREEMPT_RT and can't be acquired with disabled preemption. It is not required for correctness to invoke __blk_mq_run_hw_queue() on a CPU matching hctx->cpumask. Both (async and direct requests) can run on a CPU not matching hctx->cpumask. The CPU mask without disabling preemption and invoking __blk_mq_run_hw_queue(). Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- v1…v2: - Drop migrate_disable() as per Ming Lei. block/blk-mq.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-)