Messages in this thread | | | Date | Thu, 16 Mar 2023 18:15:48 +0100 | Subject | Re: [PATCH] tracing/hwlat: Replace sched_setaffinity with set_cpus_allowed_ptr | From | Daniel Bristot de Oliveira <> |
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On 3/16/23 15:45, Costa Shulyupin wrote: > There is a problem with the behavior of hwlat in a container, > resulting in incorrect output. A warning message is generated: > "cpumask changed while in round-robin mode, switching to mode none", > and the tracing_cpumask is ignored. This issue arises because > the kernel thread, hwlatd, is not a part of the container, and > the function sched_setaffinity is unable to locate it using its PID. > Additionally, the task_struct of hwlatd is already known. > Ultimately, the function set_cpus_allowed_ptr achieves > the same outcome as sched_setaffinity, but employs task_struct > instead of PID. > > Test case: > > # cd /sys/kernel/tracing > # echo 0 > tracing_on > # echo round-robin > hwlat_detector/mode > # echo hwlat > current_tracer > # unshare --fork --pid bash -c 'echo 1 > tracing_on' > # dmesg -c > > Actual behavior: > > [573502.809060] hwlat_detector: cpumask changed while in round-robin mode, switching to mode none > > Signed-off-by: Costa Shulyupin <costa.shul@redhat.com>
I tested it and... it works.
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Thanks -- Daniel
> --- > kernel/trace/trace_hwlat.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c > index d440ddd5fd8b..444dfc31f258 100644 > --- a/kernel/trace/trace_hwlat.c > +++ b/kernel/trace/trace_hwlat.c > @@ -339,7 +339,7 @@ static void move_to_next_cpu(void) > cpumask_clear(current_mask); > cpumask_set_cpu(next_cpu, current_mask); > > - sched_setaffinity(0, current_mask); > + set_cpus_allowed_ptr(current, current_mask); > return; > > change_mode: > @@ -446,7 +446,7 @@ static int start_single_kthread(struct trace_array *tr) > > } > > - sched_setaffinity(kthread->pid, current_mask); > + set_cpus_allowed_ptr(kthread, current_mask); > > kdata->kthread = kthread; > wake_up_process(kthread);
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