Commit 0bb0a5c1 authored by Wei Li's avatar Wei Li Committed by Steven Rostedt (Google)
Browse files

tracing/timerlat: Fix duplicated kthread creation due to CPU online/offline 

osnoise_hotplug_workfn() is the asynchronous online callback for
"trace/osnoise:online". It may be congested when a CPU goes online and
offline repeatedly and is invoked for multiple times after a certain
online.

This will lead to kthread leak and timer corruption. Add a check
in start_kthread() to prevent this situation.

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20240924094515.3561410-2-liwei391@huawei.com


Fixes: c8895e27 ("trace/osnoise: Support hotplug operations")
Signed-off-by: default avatarWei Li <liwei391@huawei.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent ad686707

kernel/trace/trace_osnoise.c

+5 −2
Original line number Diff line number Diff line
@@ -2007,6 +2007,10 @@ static int start_kthread(unsigned int cpu) 
	void *main = osnoise_main;

	char comm[24];



	/* Do not start a new thread if it is already running */

	if (per_cpu(per_cpu_osnoise_var, cpu).kthread)

		return 0;



	if (timerlat_enabled()) {

		snprintf(comm, 24, "timerlat/%d", cpu);

		main = timerlat_main;
@@ -2061,11 +2065,10 @@ static int start_per_cpu_kthreads(void) 
		if (cpumask_test_and_clear_cpu(cpu, &kthread_cpumask)) {

			struct task_struct *kthread;



			kthread = per_cpu(per_cpu_osnoise_var, cpu).kthread;

			kthread = xchg_relaxed(&(per_cpu(per_cpu_osnoise_var, cpu).kthread), NULL);

			if (!WARN_ON(!kthread))

				kthread_stop(kthread);

		}

		per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;

	}



	for_each_cpu(cpu, current_mask) {