On 01/17/2018 11:07 AM, Christian Borntraeger wrote: > > > On 01/17/2018 10:57 AM, Ming Lei wrote: >> Hi Jianchao, >> >> On Wed, Jan 17, 2018 at 04:09:11PM +0800, jianchao.wang wrote: >>> Hi ming >>> >>> Thanks for your kindly response. >>> >>> On 01/17/2018 02:22 PM, Ming Lei wrote: >>>> This warning can't be removed completely, for example, the CPU figured >>>> in blk_mq_hctx_next_cpu(hctx) can be put on again just after the >>>> following call returns and before __blk_mq_run_hw_queue() is scheduled >>>> to run. >>>> >>>> kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work, msecs_to_jiffies(msecs)) >>> We could use cpu_active in __blk_mq_run_hw_queue() to narrow the window. >>> There is a big gap between cpu_online and cpu_active. rebind_workers is also between them. >> >> This warning is harmless, also you can't reproduce it without help of your >> special patch, I guess, :-) So the window shouldn't be a big deal. > > FWIW, every WARN_ON is problematic since there are people running with panic_on_warn. To make it more clear. Every WARN_ON that can happen in real life without actually being an error is problematic. > If a condition can happen we should not use WARN_ON but something else. >
