The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x 0bb0a5c12ecf36ad561542bbb95f96355e036a02 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024100741-afoot-canal-db89@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

0bb0a5c12ecf ("tracing/timerlat: Fix duplicated kthread creation due to CPU online/offline") 177e1cc2f412 ("tracing/osnoise: Use a cpumask to know what threads are kthreads") e88ed227f639 ("tracing/timerlat: Add user-space interface") 4998e7fda149 ("tracing/osnoise: Switch from PF_NO_SETAFFINITY to migrate_disable") 30838fcd8107 ("tracing/osnoise: Add OSNOISE_WORKLOAD option") b179d48b6aab ("tracing/osnoise: Add osnoise/options file")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0bb0a5c12ecf36ad561542bbb95f96355e036a02 Mon Sep 17 00:00:00 2001 From: Wei Li liwei391@huawei.com Date: Tue, 24 Sep 2024 17:45:11 +0800 Subject: [PATCH] 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: c8895e271f79 ("trace/osnoise: Support hotplug operations") Signed-off-by: Wei Li liwei391@huawei.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org

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) {