From 43fa87f7deed52e8c8420182e0c133bc4cf395f6 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 9 Jan 2018 17:07:59 +0100 Subject: perf/core: Fix another perf,trace,cpuhp lock inversion Lockdep noticed the following 3-way lockup race: perf_trace_init() #0 mutex_lock(&event_mutex) perf_trace_event_init() perf_trace_event_reg() tp_event->class->reg() := tracepoint_probe_register #1 mutex_lock(&tracepoints_mutex) trace_point_add_func() #2 static_key_enable() #2 do_cpu_up() perf_event_init_cpu() #3 mutex_lock(&pmus_lock) #4 mutex_lock(&ctx->mutex) perf_ioctl() #4 ctx = perf_event_ctx_lock() _perf_iotcl() ftrace_profile_set_filter() #0 mutex_lock(&event_mutex) Fudge it for now by noting that the tracepoint state does not depend on the event <-> context relation. Ugly though :/ Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Signed-off-by: Ingo Molnar --- kernel/events/core.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) (limited to 'kernel/events/core.c') diff --git a/kernel/events/core.c b/kernel/events/core.c index 2d80824298a7..816f83d70fc6 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -8525,6 +8525,29 @@ fail_clear_files: return ret; } +static int +perf_tracepoint_set_filter(struct perf_event *event, char *filter_str) +{ + struct perf_event_context *ctx = event->ctx; + int ret; + + /* + * Beware, here be dragons!! + * + * the tracepoint muck will deadlock against ctx->mutex, but the tracepoint + * stuff does not actually need it. So temporarily drop ctx->mutex. As per + * perf_event_ctx_lock() we already have a reference on ctx. + * + * This can result in event getting moved to a different ctx, but that + * does not affect the tracepoint state. + */ + mutex_unlock(&ctx->mutex); + ret = ftrace_profile_set_filter(event, event->attr.config, filter_str); + mutex_lock(&ctx->mutex); + + return ret; +} + static int perf_event_set_filter(struct perf_event *event, void __user *arg) { char *filter_str; @@ -8541,8 +8564,7 @@ static int perf_event_set_filter(struct perf_event *event, void __user *arg) if (IS_ENABLED(CONFIG_EVENT_TRACING) && event->attr.type == PERF_TYPE_TRACEPOINT) - ret = ftrace_profile_set_filter(event, event->attr.config, - filter_str); + ret = perf_tracepoint_set_filter(event, filter_str); else if (has_addr_filter(event)) ret = perf_event_set_addr_filter(event, filter_str); -- cgit