Patch "trace/hwlat: make use of the helper function kthread_run_on_cpu()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    trace/hwlat: make use of the helper function kthread_run_on_cpu()

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     trace-hwlat-make-use-of-the-helper-function-kthread_.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 49db4db9d56fdb01c49514397b9d32fe2f51be13
Author: Cai Huoqing <cai.huoqing@xxxxxxxxx>
Date:   Fri Jan 14 14:03:10 2022 -0800

    trace/hwlat: make use of the helper function kthread_run_on_cpu()
    
    [ Upstream commit ff78f6679d2e223e073fcbdc8f70b6bc0abadf99 ]
    
    Replace kthread_create_on_cpu/wake_up_process() with kthread_run_on_cpu()
    to simplify the code.
    
    Link: https://lkml.kernel.org/r/20211022025711.3673-7-caihuoqing@xxxxxxxxx
    Signed-off-by: Cai Huoqing <caihuoqing@xxxxxxxxx>
    Cc: Bernard Metzler <bmt@xxxxxxxxxxxxxx>
    Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
    Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
    Cc: Doug Ledford <dledford@xxxxxxxxxx>
    Cc: Ingo Molnar <mingo@xxxxxxxxxx>
    Cc: Jason Gunthorpe <jgg@xxxxxxxx>
    Cc: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
    Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
    Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
    Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
    Cc: "Paul E . McKenney" <paulmck@xxxxxxxxxx>
    Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
    Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
    Stable-dep-of: 08697bca9bbb ("trace/hwlat: Do not start per-cpu thread if it is already running")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index 455f5edf008b8..72eeab938f1de 100644
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -491,18 +491,14 @@ static void stop_per_cpu_kthreads(void)
 static int start_cpu_kthread(unsigned int cpu)
 {
 	struct task_struct *kthread;
-	char comm[24];
 
-	snprintf(comm, 24, "hwlatd/%d", cpu);
-
-	kthread = kthread_create_on_cpu(kthread_fn, NULL, cpu, comm);
+	kthread = kthread_run_on_cpu(kthread_fn, NULL, cpu, "hwlatd/%u");
 	if (IS_ERR(kthread)) {
 		pr_err(BANNER "could not start sampling thread\n");
 		return -ENOMEM;
 	}
 
 	per_cpu(hwlat_per_cpu_data, cpu).kthread = kthread;
-	wake_up_process(kthread);
 
 	return 0;
 }