The patch below does not apply to the 5.15-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-5.15.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-amplify-possum-3dcb@gregkh' --subject-prefix 'PATCH 5.15.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") dd990352f01e ("tracing/osnoise: Make osnoise_main to sleep for microseconds") 11e4e3523da9 ("trace/osnoise: make use of the helper function kthread_run_on_cpu()") b14f4568d391 ("tracing/osnoise: Remove STACKTRACE ifdefs from inside functions") ccb6754495ef ("tracing/osnoise: Remove TIMERLAT ifdefs from inside functions") dae181349f1e ("tracing/osnoise: Support a list of trace_array *tr") 15ca4bdb0327 ("tracing/osnoise: Split workload start from the tracer start") 21ccc9cd7211 ("tracing: Disable "other" permission bits in the tracefs files")
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) {