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authorPeter Zijlstra <peterz@infradead.org>2018-01-09 17:07:59 +0100
committerIngo Molnar <mingo@kernel.org>2018-01-25 14:48:30 +0100
commit43fa87f7deed52e8c8420182e0c133bc4cf395f6 (patch)
treee756a62d69acc9e433cdc028df67c9e78dcbc2da
parentperf/core: Fix lock inversion between perf,trace,cpuhp (diff)
downloadlinux-43fa87f7deed52e8c8420182e0c133bc4cf395f6.tar.xz
linux-43fa87f7deed52e8c8420182e0c133bc4cf395f6.zip
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) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--kernel/events/core.c26
1 files changed, 24 insertions, 2 deletions
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);