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author | Peter Zijlstra <peterz@infradead.org> | 2018-01-09 17:07:59 +0100 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2018-01-25 14:48:30 +0100 |
commit | 43fa87f7deed52e8c8420182e0c133bc4cf395f6 (patch) | |
tree | e756a62d69acc9e433cdc028df67c9e78dcbc2da | |
parent | perf/core: Fix lock inversion between perf,trace,cpuhp (diff) | |
download | linux-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.c | 26 |
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); |