From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932971Ab3GBU2A (ORCPT ); Tue, 2 Jul 2013 16:28:00 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:33065 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755512Ab3GBUY1 (ORCPT ); Tue, 2 Jul 2013 16:24:27 -0400 X-Authority-Analysis: v=2.0 cv=KtrPKBqN c=1 sm=0 a=Sro2XwOs0tJUSHxCKfOySw==:17 a=Drc5e87SC40A:10 a=Ciwy3NGCPMMA:10 a=8bHPLWCpmD0A:10 a=5SG0PmZfjMsA:10 a=bbbx4UPp9XUA:10 a=meVymXHHAAAA:8 a=KGjhK52YXX0A:10 a=PUDWgdFKh_AA:10 a=20KFwNOVAAAA:8 a=VwQbUJbxAAAA:8 a=3nbZYyFuAAAA:8 a=liAV-VWemG3EvjLrsgkA:9 a=jEp0ucaQiEUA:10 a=EvKJbDF4Ut8A:10 a=jeBq3FmKZ4MA:10 a=Sro2XwOs0tJUSHxCKfOySw==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 67.255.60.225 Message-Id: <20130702202425.667999594@goodmis.org> User-Agent: quilt/0.60-1 Date: Tue, 02 Jul 2013 16:22:19 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Andrew Morton , Masami Hiramatsu , Oleg Nesterov Subject: [for-next][PATCH 03/14] tracing/kprobes: Kill probe_enable_lock References: <20130702202216.623562799@goodmis.org> Content-Disposition: inline; filename=0003-tracing-kprobes-Kill-probe_enable_lock.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oleg Nesterov 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 Signed-off-by: Oleg Nesterov Signed-off-by: Steven Rostedt --- kernel/trace/trace_kprobe.c | 43 ++++++++++++++++++++----------------------- 1 file changed, 20 insertions(+), 23 deletions(-) diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index c35bebe..282f86c 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; -- 1.7.10.4