diff options
author | Oleg Nesterov <oleg@redhat.com> | 2013-06-20 21:38:09 +0400 |
---|---|---|
committer | Steven Rostedt <rostedt@goodmis.org> | 2013-07-02 04:34:24 +0400 |
commit | 3fe3d6193e7cd7b4dd2bde10772f048bdefea4ee (patch) | |
tree | f7623a40ffb23ffab302a8cb9ed6c5716ec1d691 /kernel/trace | |
parent | 288e984e622336bab8bc3dfdf2f190816362d9a1 (diff) | |
download | linux-3fe3d6193e7cd7b4dd2bde10772f048bdefea4ee.tar.xz |
tracing/kprobes: Kill probe_enable_lock
enable_trace_probe() and disable_trace_probe() should not worry about
serialization, the caller (perf_trace_init or __ftrace_set_clr_event)
holds event_mutex.
They are also called by kprobe_trace_self_tests_init(), but this __init
function can't race with itself or trace_events.c
And note that this code depended on event_mutex even before 41a7dd420c
which introduced probe_enable_lock. In fact it assumes that the caller
kprobe_register() can never race with itself. Otherwise, say, tp->flags
manipulations are racy.
Link: http://lkml.kernel.org/r/20130620173809.GA13158@redhat.com
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r-- | kernel/trace/trace_kprobe.c | 43 |
1 files changed, 20 insertions, 23 deletions
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index c35bebe53ffe..282f86cfd304 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -183,16 +183,15 @@ static struct trace_probe *find_trace_probe(const char *event, return NULL; } +/* + * This and enable_trace_probe/disable_trace_probe rely on event_mutex + * held by the caller, __ftrace_set_clr_event(). + */ static int trace_probe_nr_files(struct trace_probe *tp) { - struct ftrace_event_file **file; + struct ftrace_event_file **file = rcu_dereference_raw(tp->files); int ret = 0; - /* - * Since all tp->files updater is protected by probe_enable_lock, - * we don't need to lock an rcu_read_lock. - */ - file = rcu_dereference_raw(tp->files); if (file) while (*(file++)) ret++; @@ -200,8 +199,6 @@ static int trace_probe_nr_files(struct trace_probe *tp) return ret; } -static DEFINE_MUTEX(probe_enable_lock); - /* * Enable trace_probe * if the file is NULL, enable "perf" handler, or enable "trace" handler. @@ -211,8 +208,6 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) { int ret = 0; - mutex_lock(&probe_enable_lock); - if (file) { struct ftrace_event_file **new, **old; int n = trace_probe_nr_files(tp); @@ -223,7 +218,7 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) GFP_KERNEL); if (!new) { ret = -ENOMEM; - goto out_unlock; + goto out; } memcpy(new, old, n * sizeof(struct ftrace_event_file *)); new[n] = file; @@ -246,10 +241,7 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) else ret = enable_kprobe(&tp->rp.kp); } - - out_unlock: - mutex_unlock(&probe_enable_lock); - + out: return ret; } @@ -282,8 +274,6 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) { int ret = 0; - mutex_lock(&probe_enable_lock); - if (file) { struct ftrace_event_file **new, **old; int n = trace_probe_nr_files(tp); @@ -292,7 +282,7 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) old = rcu_dereference_raw(tp->files); if (n == 0 || trace_probe_file_index(tp, file) < 0) { ret = -EINVAL; - goto out_unlock; + goto out; } if (n == 1) { /* Remove the last file */ @@ -303,7 +293,7 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) GFP_KERNEL); if (!new) { ret = -ENOMEM; - goto out_unlock; + goto out; } /* This copy & check loop copies the NULL stopper too */ @@ -326,10 +316,7 @@ disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) else disable_kprobe(&tp->rp.kp); } - - out_unlock: - mutex_unlock(&probe_enable_lock); - + out: return ret; } @@ -1214,6 +1201,12 @@ kretprobe_perf_func(struct trace_probe *tp, struct kretprobe_instance *ri, } #endif /* CONFIG_PERF_EVENTS */ +/* + * called by perf_trace_init() or __ftrace_set_clr_event() under event_mutex. + * + * kprobe_trace_self_tests_init() does enable_trace_probe/disable_trace_probe + * lockless, but we can't race with this __init function. + */ static __kprobes int kprobe_register(struct ftrace_event_call *event, enum trace_reg type, void *data) @@ -1379,6 +1372,10 @@ find_trace_probe_file(struct trace_probe *tp, struct trace_array *tr) return NULL; } +/* + * Nobody but us can call enable_trace_probe/disable_trace_probe at this + * stage, we can do this lockless. + */ static __init int kprobe_trace_self_tests_init(void) { int ret, warn = 0; |