Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756152Ab3G2R4i (ORCPT ); Mon, 29 Jul 2013 13:56:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:9179 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753259Ab3G2R4h (ORCPT ); Mon, 29 Jul 2013 13:56:37 -0400 Date: Mon, 29 Jul 2013 19:50:33 +0200 From: Oleg Nesterov To: Steven Rostedt , Masami Hiramatsu Cc: Alexander Z Lam , Arnaldo Carvalho de Melo , David Sharp , Frederic Weisbecker , Greg Kroah-Hartman , Ingo Molnar , Peter Zijlstra , Srikar Dronamraju , Vaibhav Nagarnaik , "zhangwei(Jovi)" , linux-kernel@vger.kernel.org Subject: [PATCH v2 1/1] tracing: trace_remove_event_call() should fail if call/file is in use Message-ID: <20130729175033.GB26284@redhat.com> References: <20130729175008.GA26284@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130729175008.GA26284@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3356 Lines: 100 Change trace_remove_event_call(call) to return the error if this call is active. This is what the callers assume but can't verify outside of the tracing locks. Both trace_kprobe.c/trace_uprobe.c need the additional changes, unregister_trace_probe() should abort if trace_remove_event_call() fails. The caller is going to free this call/file so we must ensure that nobody can use them after trace_remove_event_call() succeeds. debugfs should be fine after the previous changes and event_remove() does TRACE_REG_UNREGISTER, but still there are 2 reasons why we need the additional checks: - There could be a perf_event(s) attached to this tp_event, so the patch checks ->perf_refcount. - TRACE_REG_UNREGISTER can be suppressed by FTRACE_EVENT_FL_SOFT_MODE, so we simply check FTRACE_EVENT_FL_ENABLED protected by event_mutex. Signed-off-by: Oleg Nesterov --- include/linux/ftrace_event.h | 2 +- kernel/trace/trace_events.c | 35 +++++++++++++++++++++++++++++++++-- 2 files changed, 34 insertions(+), 3 deletions(-) diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h index 4372658..f98ab06 100644 --- a/include/linux/ftrace_event.h +++ b/include/linux/ftrace_event.h @@ -332,7 +332,7 @@ extern int trace_define_field(struct ftrace_event_call *call, const char *type, const char *name, int offset, int size, int is_signed, int filter_type); extern int trace_add_event_call(struct ftrace_event_call *call); -extern void trace_remove_event_call(struct ftrace_event_call *call); +extern int trace_remove_event_call(struct ftrace_event_call *call); #define is_signed_type(type) (((type)(-1)) < (type)1) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 79a2743..3450496 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -1709,16 +1709,47 @@ static void __trace_remove_event_call(struct ftrace_event_call *call) destroy_preds(call); } +static int probe_remove_event_call(struct ftrace_event_call *call) +{ + struct trace_array *tr; + struct ftrace_event_file *file; + +#ifdef CONFIG_PERF_EVENTS + if (call->perf_refcount) + return -EBUSY; +#endif + do_for_each_event_file(tr, file) { + if (file->event_call != call) + continue; + /* + * We can't rely on ftrace_event_enable_disable(enable => 0) + * we are going to do, FTRACE_EVENT_FL_SOFT_MODE can suppress + * TRACE_REG_UNREGISTER. + */ + if (file->flags & FTRACE_EVENT_FL_ENABLED) + return -EBUSY; + break; + } while_for_each_event_file(); + + __trace_remove_event_call(call); + + return 0; +} + /* Remove an event_call */ -void trace_remove_event_call(struct ftrace_event_call *call) +int trace_remove_event_call(struct ftrace_event_call *call) { + int ret; + mutex_lock(&trace_types_lock); mutex_lock(&event_mutex); down_write(&trace_event_sem); - __trace_remove_event_call(call); + ret = probe_remove_event_call(call); up_write(&trace_event_sem); mutex_unlock(&event_mutex); mutex_unlock(&trace_types_lock); + + return ret; } #define for_each_event(event, start, end) \ -- 1.5.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/