trace/hwlat: Do not wipe the contents of per-cpu thread data

commit 4c42f5f0d1dd20bddd9f940beb1e6ccad60c4498 upstream.

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.intel.com/
Link: https://lkml.kernel.org/r/20230310100451.3948583-2-tero.kristo@linux.intel.com
Cc: stable@vger.kernel.org
Fixes: f46b16520a087 ("trace/hwlat: Implement the per-cpu mode")
Signed-off-by: Tero Kristo <tero.kristo@linux.intel.com>
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index d0a730d99a33144621507e71918126952c304909..11f32e947c45290d5f725608bce580214e328955 100644 (file)
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -588,9 +588,6 @@ 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)