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authorCosta Shulyupin <costa.shul@redhat.com>2023-03-16 16:45:35 +0200
committerSteven Rostedt (Google) <rostedt@goodmis.org>2023-03-19 13:23:22 -0400
commit71c7a30442b724717a30d5e7d1662ba4904eb3d4 (patch)
treebab998bca01e9c6bf01841446382bdcbc5c9d7e6 /kernel
parenta98151ad53b53f010ee364ec2fd06445b328578b (diff)
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace_hwlat.c4
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);