From: "Steven Rostedt (VMware)" <[email protected]> The event_mutex is a high level lock. It should never be taken under get_online_cpus() being held. Perf is the only user that does so. Move the taking of event_mutex outside of get_online_cpus() and this should solve the locking order.
Signed-off-by: Steven Rostedt (VMware) <[email protected]> --- include/linux/trace_events.h | 2 ++ kernel/events/core.c | 9 +++++++++ kernel/trace/trace.h | 1 - kernel/trace/trace_event_perf.c | 8 ++++---- 4 files changed, 15 insertions(+), 5 deletions(-) diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index a556805eff8a..0a30d2b5df51 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -50,6 +50,8 @@ struct trace_event; int trace_raw_output_prep(struct trace_iterator *iter, struct trace_event *event); +extern struct mutex event_mutex; + /* * The trace entry - the most basic unit of tracing. This is what * is printed in the end as a single line in the trace output, such as: diff --git a/kernel/events/core.c b/kernel/events/core.c index dba870ccda63..c65c3b5a92f4 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4021,12 +4021,14 @@ static void unaccount_event(struct perf_event *event) static void perf_sched_delayed(struct work_struct *work) { + mutex_lock(&event_mutex); get_online_cpus(); mutex_lock(&perf_sched_mutex); if (atomic_dec_and_test(&perf_sched_count)) static_branch_disable_cpuslocked(&perf_sched_events); mutex_unlock(&perf_sched_mutex); put_online_cpus(); + mutex_unlock(&event_mutex); } /* @@ -4231,7 +4233,9 @@ static void put_event(struct perf_event *event) if (!atomic_long_dec_and_test(&event->refcount)) return; + mutex_lock(&event_mutex); _free_event(event); + mutex_unlock(&event_mutex); } /* @@ -8917,6 +8921,7 @@ perf_event_mux_interval_ms_store(struct device *dev, pmu->hrtimer_interval_ms = timer; /* update all cpuctx for this PMU */ + mutex_lock(&event_mutex); get_online_cpus(); for_each_online_cpu(cpu) { struct perf_cpu_context *cpuctx; @@ -8927,6 +8932,7 @@ perf_event_mux_interval_ms_store(struct device *dev, (remote_function_f)perf_mux_hrtimer_restart, cpuctx); } put_online_cpus(); + mutex_unlock(&event_mutex); mutex_unlock(&mux_interval_mutex); return count; @@ -9879,6 +9885,7 @@ SYSCALL_DEFINE5(perf_event_open, goto err_task; } + mutex_lock(&event_mutex); get_online_cpus(); if (task) { @@ -10160,6 +10167,7 @@ SYSCALL_DEFINE5(perf_event_open, } put_online_cpus(); + mutex_unlock(&event_mutex); mutex_lock(¤t->perf_event_mutex); list_add_tail(&event->owner_entry, ¤t->perf_event_list); @@ -10196,6 +10204,7 @@ SYSCALL_DEFINE5(perf_event_open, mutex_unlock(&task->signal->cred_guard_mutex); err_cpus: put_online_cpus(); + mutex_lock(&event_mutex); err_task: if (task) put_task_struct(task); diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 291a1bca5748..4df0a8e9d000 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1430,7 +1430,6 @@ static inline void *event_file_data(struct file *filp) return ACCESS_ONCE(file_inode(filp)->i_private); } -extern struct mutex event_mutex; extern struct list_head ftrace_events; extern const struct file_operations event_trigger_fops; diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c index 562fa69df5d3..b8c90a024e99 100644 --- a/kernel/trace/trace_event_perf.c +++ b/kernel/trace/trace_event_perf.c @@ -213,7 +213,8 @@ int perf_trace_init(struct perf_event *p_event) u64 event_id = p_event->attr.config; int ret = -EINVAL; - mutex_lock(&event_mutex); + lockdep_assert_held(&event_mutex); + list_for_each_entry(tp_event, &ftrace_events, list) { if (tp_event->event.type == event_id && tp_event->class && tp_event->class->reg && @@ -224,17 +225,16 @@ int perf_trace_init(struct perf_event *p_event) break; } } - mutex_unlock(&event_mutex); return ret; } void perf_trace_destroy(struct perf_event *p_event) { - mutex_lock(&event_mutex); + lockdep_assert_held(&event_mutex); + perf_trace_event_close(p_event); perf_trace_event_unreg(p_event); - mutex_unlock(&event_mutex); } int perf_trace_add(struct perf_event *p_event, int flags) -- 2.10.2
