Messages in this thread Patch in this message | | | Date | Wed, 2 Sep 2020 12:05:16 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH] perf/core: Fix hung issue on perf stat command during cpu hotplug |
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Em Thu, Aug 27, 2020 at 12:17:32PM +0530, Kajol Jain escreveu: > 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.
I reproduced this issue with v5.9-rc3, now have to reboot for a conf call, will try to test the patch afterwards,
[65108.467416] IRQ 165: no longer affine to CPU23 [65108.468495] smpboot: CPU 23 is now offline [65129.003879] Uhhuh. NMI received for unknown reason 1c on CPU 20. [65129.003880] Do you have a strange power saving mode enabled? [65129.003880] Dazed and confused, but trying to continue [65156.155539] Uhhuh. NMI received for unknown reason 1c on CPU 2. [65156.155539] Do you have a strange power saving mode enabled? [65156.155540] Dazed and confused, but trying to continue [65161.985284] Uhhuh. NMI received for unknown reason 1c on CPU 21. [65161.985285] Do you have a strange power saving mode enabled? [65161.985285] Dazed and confused, but trying to continue [65183.154444] Uhhuh. NMI received for unknown reason 1c on CPU 1. [65183.154445] Do you have a strange power saving mode enabled? [65183.154446] Dazed and confused, but trying to continue [65189.724797] Uhhuh. NMI received for unknown reason 0c on CPU 4. [65189.724798] Do you have a strange power saving mode enabled? [65189.724799] Dazed and confused, but trying to continue [65196.259918] Uhhuh. NMI received for unknown reason 1c on CPU 11. [65196.259918] Do you have a strange power saving mode enabled? [65196.259918] Dazed and confused, but trying to continue [65234.794490] Uhhuh. NMI received for unknown reason 0c on CPU 5. [65234.794491] Do you have a strange power saving mode enabled? [65234.794491] Dazed and confused, but trying to continue [65454.559831] Uhhuh. NMI received for unknown reason 1c on CPU 19. [65454.559832] Do you have a strange power saving mode enabled? [65454.559832] Dazed and confused, but trying to continue [65529.657789] Uhhuh. NMI received for unknown reason 1c on CPU 3. [65529.657790] Do you have a strange power saving mode enabled? [65529.657790] Dazed and confused, but trying to continue [acme@five perf]$
Things seems to be working again after bringing that CPU back online:
[root@five ~]# perf top --stdio -C 0-22 Error: The sys_perf_event_open() syscall returned with 16 (Device or resource busy) for event (cycles). /bin/dmesg | grep -i perf may provide additional information.
[root@five ~]# perf stat -e cycles sleep 1 Error: The sys_perf_event_open() syscall returned with 16 (Device or resource busy) for event (cycles). /bin/dmesg | grep -i perf may provide additional information.
[root@five ~]# perf record -e cycles sleep 1 Error: The sys_perf_event_open() syscall returned with 16 (Device or resource busy) for event (cycles). /bin/dmesg | grep -i perf may provide additional information.
[root@five ~]# echo 1 > /sys/devices/system/cpu/cpu23/online [root@five ~]# perf record -e cycles sleep 1 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.039 MB perf.data (7 samples) ] [root@five ~]# perf stat -e cycles sleep 1
Performance counter stats for 'sleep 1':
842,743 cycles
1.000903853 seconds time elapsed
0.000902000 seconds user 0.000000000 seconds sys
[root@five ~]# perf stat -e cycles sleep 1
- Arnaldo
> 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> > Reviewed-by: Barret Rhoden <brho@google.com> > Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> > --- > kernel/events/core.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > Changelog: > - Remove RFC tag > - Resolve some nits issues like space after if and > added -ENXIO in comment msg of function 'task_function_call' > as suggested by Barret Rhoden. > > Link to the RFC: https://lkml.org/lkml/2020/8/26/896 > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 5bfe8e3c6e44..cef646084198 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -99,7 +99,7 @@ static void remote_function(void *data) > * retry due to any failures in smp_call_function_single(), such as if the > * task_cpu() goes offline concurrently. > * > - * returns @func return value or -ESRCH when the process isn't running > + * returns @func return value or -ESRCH or -ENXIO when the process isn't running > */ > static int > task_function_call(struct task_struct *p, remote_function_f func, void *info) > @@ -115,7 +115,8 @@ task_function_call(struct task_struct *p, remote_function_f func, void *info) > for (;;) { > ret = smp_call_function_single(task_cpu(p), remote_function, > &data, 1); > - ret = !ret ? data.ret : -EAGAIN; > + if (!ret) > + ret = data.ret; > > if (ret != -EAGAIN) > break; > -- > 2.26.2 >
--
- Arnaldo
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