• G
    blk-mq: Always schedule hctx->next_cpu · c02ebfdd
    Gabriel Krisman Bertazi 提交于
    Commit 0e87e58b ("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: 0e87e58b ("blk-mq: improve warning for running a queue on the wrong CPU")
    Signed-off-by: NGabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
    Signed-off-by: NJens Axboe <axboe@fb.com>
    c02ebfdd
blk-mq.c 57.9 KB