]> git.karo-electronics.de Git - linux-beck.git/commit
blk-mq: Always schedule hctx->next_cpu
authorGabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
Wed, 28 Sep 2016 03:24:24 +0000 (00:24 -0300)
committerJens Axboe <axboe@fb.com>
Sun, 6 Nov 2016 21:14:41 +0000 (14:14 -0700)
commitc02ebfdddbafa9a6a0f52fbd715e6bfa229af9d3
tree2a9a2528b8e404043a53d26d06fc4aeba5340610
parentd278d4a8892f13b6a9eb6102b356402f0e062324
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>
block/blk-mq.c