From: Tero Kristo <tero.kristo(a)linux.intel.com>
The hwlatd tracer will end up starting multiple per-cpu threads with
the following script:
#!/bin/sh
cd /sys/kernel/debug/tracing
echo 0 > tracing_on
echo hwlat > current_tracer
echo per-cpu > hwlat_detector/mode
echo 100000 > hwlat_detector/width
echo 200000 > hwlat_detector/window
echo 1 > tracing_on
To fix the issue, check if the hwlatd thread for the cpu is already
running, before starting a new one. Along with the previous patch, this
avoids running multiple instances of the same CPU thread on the system.
Link: https://lore.kernel.org/all/20230302113654.2984709-1-tero.kristo@linux.inte…
Link: https://lkml.kernel.org/r/20230310100451.3948583-3-tero.kristo@linux.intel.…
Cc: stable(a)vger.kernel.org
Fixes: f46b16520a087 ("trace/hwlat: Implement the per-cpu mode")
Signed-off-by: Tero Kristo <tero.kristo(a)linux.intel.com>
Acked-by: Daniel Bristot de Oliveira <bristot(a)kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt(a)goodmis.org>
---
kernel/trace/trace_hwlat.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index edc26dc22c3f..c4945f8adc11 100644
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -492,6 +492,10 @@ static int start_cpu_kthread(unsigned int cpu)
{
struct task_struct *kthread;
+ /* Do not start a new hwlatd thread if it is already running */
+ if (per_cpu(hwlat_per_cpu_data, cpu).kthread)
+ return 0;
+
kthread = kthread_run_on_cpu(kthread_fn, NULL, cpu, "hwlatd/%u");
if (IS_ERR(kthread)) {
pr_err(BANNER "could not start sampling thread\n");
--
2.39.1
From: Tero Kristo <tero.kristo(a)linux.intel.com>
Do not wipe the contents of the per-cpu kthread data when starting the
tracer, as this will completely forget about already running instances
and can later start new additional per-cpu threads.
Link: https://lore.kernel.org/all/20230302113654.2984709-1-tero.kristo@linux.inte…
Link: https://lkml.kernel.org/r/20230310100451.3948583-2-tero.kristo@linux.intel.…
Cc: stable(a)vger.kernel.org
Fixes: f46b16520a087 ("trace/hwlat: Implement the per-cpu mode")
Signed-off-by: Tero Kristo <tero.kristo(a)linux.intel.com>
Acked-by: Daniel Bristot de Oliveira <bristot(a)kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt(a)goodmis.org>
---
kernel/trace/trace_hwlat.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index d440ddd5fd8b..edc26dc22c3f 100644
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -584,9 +584,6 @@ static int start_per_cpu_kthreads(struct trace_array *tr)
*/
cpumask_and(current_mask, cpu_online_mask, tr->tracing_cpumask);
- for_each_online_cpu(cpu)
- per_cpu(hwlat_per_cpu_data, cpu).kthread = NULL;
-
for_each_cpu(cpu, current_mask) {
retval = start_cpu_kthread(cpu);
if (retval)
--
2.39.1