__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@xxxxxxxxxxxxx>
---
v1…v2:
- Drop migrate_disable() as per Ming Lei.
block/blk-mq.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
--- 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,
