Messages in this thread | | | Date | Thu, 27 Aug 2020 11:17:42 +0530 | From | Srikar Dronamraju <> | Subject | Re: [RFC v2] perf/core: Fixes hung issue on perf stat command during cpu hotplug |
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* Kajol Jain <kjain@linux.ibm.com> [2020-08-26 20:24:11]:
> Commit 2ed6edd33a21 ("perf: Add cond_resched() to task_function_call()") > added assignment of ret value as -EAGAIN in case function > call to 'smp_call_function_single' fails. > For non-zero ret value, it did > 'ret = !ret ? data.ret : -EAGAIN;', which always > assign -EAGAIN to ret and make second if condition useless. > > In scenarios like when executing a perf stat with --per-thread option, and > if any of the monitoring cpu goes offline, the 'smp_call_function_single' > function could return -ENXIO, and with the above check, > task_function_call hung and increases CPU > usage (because of repeated 'smp_call_function_single()') > > Recration scenario: > # perf stat -a --per-thread && (offline a CPU ) > > Patch here removes the tertiary condition added as part of that > commit and added a check for NULL and -EAGAIN. > > Fixes: 2ed6edd33a21("perf: Add cond_resched() to task_function_call()") > Signed-off-by: Kajol Jain <kjain@linux.ibm.com> > Reported-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
-- Thanks and Regards Srikar Dronamraju
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