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tracing/timerlat: Drop interface_lock in stop_kthread()

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stop_kthread() is the offline callback for "trace/osnoise:online", since
commit 5bfbcd1ee5 ("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: 5bfbcd1ee5 ("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>
This commit is contained in:
Wei Li 2024-09-24 17:45:12 +08:00 committed by Steven Rostedt (Google)
parent 0bb0a5c12e
commit b484a02c9c
1 changed files with 6 additions and 7 deletions
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13
kernel/trace/trace_osnoise.c
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@ -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();
}
/*