From: Wei Li liwei391@huawei.com

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: c8895e271f79 ("trace/osnoise: Support hotplug operations") Signed-off-by: Wei Li liwei391@huawei.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org --- kernel/trace/trace_osnoise.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c index 1439064f65d6..d1a539913a5f 100644 --- a/kernel/trace/trace_osnoise.c +++ b/kernel/trace/trace_osnoise.c @@ -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) {