tracing: Quiet smp_processor_id() use in preemptable warning in hwlat

The hardware latency detector (hwlat) has a mode that it runs one thread
across CPUs. The logic to move from the currently running CPU to the next
one in the list does a smp_processor_id() to find where it currently is.
Unfortunately, it's done with preemption enabled, and this triggers a
warning for using smp_processor_id() in a preempt enabled section.

As it is only using smp_processor_id() to get information on where it
currently is in order to simply move it to the next CPU, it doesn't really
care if it got moved in the mean time. It will simply balance out later if
such a case arises.

Switch smp_processor_id() to raw_smp_processor_id() to quiet that warning.

Link: https://lkml.kernel.org/r/20210804141848.79edadc0@oasis.local.home
Acked-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Fixes: 9bde8ed05529 ("trace/hwlat: Implement the mode config option")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index a6c0cdaf4b8782f71196123a3a2816deff279ccf..14f46aae1981f8ef61be8bcb0ff59e6e5e5c525e 100644 (file)
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -327,7 +327,7 @@ static void move_to_next_cpu(void)
 
        get_online_cpus();
        cpumask_and(current_mask, cpu_online_mask, tr->tracing_cpumask);
-       next_cpu = cpumask_next(smp_processor_id(), current_mask);
+       next_cpu = cpumask_next(raw_smp_processor_id(), current_mask);
        put_online_cpus();
 
        if (next_cpu >= nr_cpu_ids)