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| author | Gabriel Krisman Bertazi <krisman@linux.vnet.ibm.com> | 2016-09-28 05:24:24 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2016-11-06 22:14:41 +0100 |
| commit | c02ebfdddbafa9a6a0f52fbd715e6bfa229af9d3 (patch) | |
| tree | 2a9a2528b8e404043a53d26d06fc4aeba5340610 | |
| parent | block: add code to track actual device queue depth (diff) | |
| download | linux-c02ebfdddbafa9a6a0f52fbd715e6bfa229af9d3.tar.xz linux-c02ebfdddbafa9a6a0f52fbd715e6bfa229af9d3.zip | |
blk-mq: Always schedule hctx->next_cpu
Commit 0e87e58bf60e ("blk-mq: improve warning for running a queue on the
wrong CPU") attempts to avoid triggering the WARN_ON in
__blk_mq_run_hw_queue when the expected CPU is dead. Problem is, in the
last batch execution before round robin, blk_mq_hctx_next_cpu can
schedule a dead CPU and also update next_cpu to the next alive CPU in
the mask, which will trigger the WARN_ON despite the previous
workaround.
The following patch fixes this scenario by always scheduling the value
in hctx->next_cpu. This changes the moment when we round-robin the CPU
running the hctx, but it really doesn't matter, since it still executes
BLK_MQ_CPU_WORK_BATCH times in a row before switching to another CPU.
Fixes: 0e87e58bf60e ("blk-mq: improve warning for running a queue on the wrong CPU")
Signed-off-by: Gabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
| -rw-r--r-- | block/blk-mq.c | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index 077c2416a955..6f5cb3f3dcac 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -929,7 +929,7 @@ static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx) return WORK_CPU_UNBOUND; if (--hctx->next_cpu_batch <= 0) { - int cpu = hctx->next_cpu, next_cpu; + int next_cpu; next_cpu = cpumask_next(hctx->next_cpu, hctx->cpumask); if (next_cpu >= nr_cpu_ids) @@ -937,8 +937,6 @@ static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx) hctx->next_cpu = next_cpu; hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH; - - return cpu; } return hctx->next_cpu; |