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| author |   Costa Shulyupin <costa.shul@redhat.com> | 2023-03-16 16:45:35 +0200 |
|---|---|---|
| committer |   Steven Rostedt (Google) <rostedt@goodmis.org> | 2023-03-19 13:23:22 -0400 |
| commit | 71c7a30442b724717a30d5e7d1662ba4904eb3d4 (patch) | |
| tree | bab998bca01e9c6bf01841446382bdcbc5c9d7e6 | |
| parent | ring-buffer: remove obsolete comment for free_buffer_page() (diff) | |
| download | linux-stable-71c7a30442b724717a30d5e7d1662ba4904eb3d4.tar.xz linux-stable-71c7a30442b724717a30d5e7d1662ba4904eb3d4.zip | |
tracing/hwlat: Replace sched_setaffinity with set_cpus_allowed_ptr
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
Link: https://lore.kernel.org/linux-trace-kernel/20230316144535.1004952-1-costa.shul@redhat.com
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: 0330f7aa8ee63 ("tracing: Have hwlat trace migrate across tracing_cpumask CPUs")
Signed-off-by: Costa Shulyupin <costa.shul@redhat.com>
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
| -rw-r--r-- | kernel/trace/trace_hwlat.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c index c4945f8adc11..2f37a6e68aa9 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); |