From: Wei Li liwei391@huawei.com
stop_kthread() is the offline callback for "trace/osnoise:online", since commit 5bfbcd1ee57b ("tracing/timerlat: Add interface_lock around clearing of kthread in stop_kthread()"), the following ABBA deadlock scenario is introduced:
T1 | T2 [BP] | T3 [AP] osnoise_hotplug_workfn() | work_for_cpu_fn() | cpuhp_thread_fun() | _cpu_down() | osnoise_cpu_die() mutex_lock(&interface_lock) | | stop_kthread() | cpus_write_lock() | mutex_lock(&interface_lock) cpus_read_lock() | cpuhp_kick_ap() |
As the interface_lock here in just for protecting the "kthread" field of the osn_var, use xchg() instead to fix this issue. Also use for_each_online_cpu() back in stop_per_cpu_kthreads() as it can take cpu_read_lock() again.
Cc: stable@vger.kernel.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Link: https://lore.kernel.org/20240924094515.3561410-3-liwei391@huawei.com Fixes: 5bfbcd1ee57b ("tracing/timerlat: Add interface_lock around clearing of kthread in stop_kthread()") Signed-off-by: Wei Li liwei391@huawei.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org --- kernel/trace/trace_osnoise.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c index d1a539913a5f..e22567174dd3 100644 --- a/kernel/trace/trace_osnoise.c +++ b/kernel/trace/trace_osnoise.c @@ -1953,12 +1953,8 @@ static void stop_kthread(unsigned int cpu) { struct task_struct *kthread;
- mutex_lock(&interface_lock); - kthread = per_cpu(per_cpu_osnoise_var, cpu).kthread; + kthread = xchg_relaxed(&(per_cpu(per_cpu_osnoise_var, cpu).kthread), NULL); if (kthread) { - per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL; - mutex_unlock(&interface_lock); - if (cpumask_test_and_clear_cpu(cpu, &kthread_cpumask) && !WARN_ON(!test_bit(OSN_WORKLOAD, &osnoise_options))) { kthread_stop(kthread); @@ -1972,7 +1968,6 @@ static void stop_kthread(unsigned int cpu) put_task_struct(kthread); } } else { - mutex_unlock(&interface_lock); /* if no workload, just return */ if (!test_bit(OSN_WORKLOAD, &osnoise_options)) { /* @@ -1994,8 +1989,12 @@ static void stop_per_cpu_kthreads(void) { int cpu;
- for_each_possible_cpu(cpu) + cpus_read_lock(); + + for_each_online_cpu(cpu) stop_kthread(cpu); + + cpus_read_unlock(); }
/*