[PATCH] tracing/osnoise: fix potential deadlock in cpu hotplug
STALE190d
From: <hidden>
Date: 2026-03-24 07:14:45
Also in:
lkml
Subsystem:
the rest, tracing, tracing os noise / latency tracers · Maintainers:
Linus Torvalds, Steven Rostedt, Masami Hiramatsu
From: luohaiyang10243395 <redacted>
The following sequence may leads deadlock in cpu hotplug:
CPU0 | CPU1
| schedule_work_on
|
_cpu_down//set CPU1 offline |
cpus_write_lock |
| osnoise_hotplug_workfn
| mutex_lock(&interface_lock);
| cpus_read_lock(); //wait cpu_hotplug_lock
|
| cpuhp/1
| osnoise_cpu_die
| kthread_stop
| wait_for_completion //wait osnoise/1 exit
|
| osnoise/1
| osnoise_sleep
| mutex_lock(&interface_lock); //deadlock
Fix by swap the order of cpus_read_lock() and mutex_lock(&interface_lock).
Signed-off-by: Luo Haiyang <redacted>
---
kernel/trace/trace_osnoise.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index dee610e465b9..be6cf0bb3c03 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c@@ -2073,8 +2073,8 @@ static void osnoise_hotplug_workfn(struct work_struct *dummy) if (!osnoise_has_registered_instances()) return; - guard(mutex)(&interface_lock); guard(cpus_read_lock)(); + guard(mutex)(&interface_lock); if (!cpu_online(cpu)) return;
@@ -2237,11 +2237,11 @@ static ssize_t osnoise_options_write(struct file *filp, const char __user *ubuf, if (running) stop_per_cpu_kthreads(); - mutex_lock(&interface_lock); /* * avoid CPU hotplug operations that might read options. */ cpus_read_lock(); + mutex_lock(&interface_lock); retval = cnt;
@@ -2257,8 +2257,8 @@ static ssize_t osnoise_options_write(struct file *filp, const char __user *ubuf, clear_bit(option, &osnoise_options); } - cpus_read_unlock(); mutex_unlock(&interface_lock); + cpus_read_unlock(); if (running) start_per_cpu_kthreads();
@@ -2345,16 +2345,16 @@ osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count, if (running) stop_per_cpu_kthreads(); - mutex_lock(&interface_lock); /* * osnoise_cpumask is read by CPU hotplug operations. */ cpus_read_lock(); + mutex_lock(&interface_lock); cpumask_copy(&osnoise_cpumask, osnoise_cpumask_new); - cpus_read_unlock(); mutex_unlock(&interface_lock); + cpus_read_unlock(); if (running) start_per_cpu_kthreads();
--
2.25.1