diff options
| author | Gabriel Krisman Bertazi <krisman@linux.vnet.ibm.com> | 2016-09-28 00:24:24 -0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-01-19 20:18:07 +0100 |
| commit | d9c19f90f3a50eb4ff8d17616492338c0b2f9434 (patch) | |
| tree | 3a4c6783db9c7970a0c4af0b36564d5a4482a4aa | |
| parent | cb50d45c3d42633830ca60b34bf46c14941cdde4 (diff) | |
blk-mq: Always schedule hctx->next_cpu
commit c02ebfdddbafa9a6a0f52fbd715e6bfa229af9d3 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -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 ad459e4e8071..81caceb96c3c 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -895,7 +895,7 @@ 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) @@ -903,8 +903,6 @@ 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; |