Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754606Ab3F1Oco (ORCPT ); Fri, 28 Jun 2013 10:32:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:61463 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751743Ab3F1Ocn (ORCPT ); Fri, 28 Jun 2013 10:32:43 -0400 Date: Fri, 28 Jun 2013 16:27:44 +0200 From: Oleg Nesterov To: Masami Hiramatsu Cc: Steven Rostedt , Frederic Weisbecker , "zhangwei(Jovi)" , Ingo Molnar , Srikar Dronamraju , lkml Subject: Re: [PATCH] tracing/kprobe: Recover old array if fails to enable kprobe Message-ID: <20130628142744.GA19278@redhat.com> References: <51CD25A6.2030907@hitachi.com> <20130628130452.1132.85665.stgit@mhiramat-M0-7522> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130628130452.1132.85665.stgit@mhiramat-M0-7522> 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: 2329 Lines: 67 On 06/28, Masami Hiramatsu wrote: > > @@ -232,19 +246,21 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) > rcu_assign_pointer(tp->files, new); > tp->flags |= TP_FLAG_TRACE; > > + ret = __enable_trace_probe(tp); > + if (ret < 0) { > + /* Write back the old list */ > + rcu_assign_pointer(tp->files, old); > + old = new; /* "new" must be freed */ > + } > + > if (old) { > /* Make sure the probe is done with old files */ > synchronize_sched(); > kfree(old); > } Ah, but this conflicts with the other changes I sent. They have your acks, and iiuc Steven is going to apply them. Besides, this fix is not complete afaics, we should also clear TP_FLAG_TRACE/PROFILE if __enable_trace_probe() fails. Perhaps you can do this later, on top of the pending changes? Or. Given that this patch assumes that enable_kprobe() must succed, can't we make a minimal change for now? ------------------------------------------------------------------------------- [PATCH] tracing/kprobe: WARN() if enable_kprobe() fails. enable_trace_probe() doesn't recover tp->files/flags if enable_kprobe() fails, this looks confusing. However, enable_kprobe() must not fail at this time except for unknown bug or changing the implementation of enable_kprobe(), because usual failure cases (not registered or gone) are already filtered. So this patch simply adds WARN_ON(ret) to document this fact, even if it makes sense to cleanup the logic anyway later. Reported-by: Srikar Dronamraju Signed-off-by: Oleg Nesterov --- kernel/trace/trace_kprobe.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index 5c070db..bb608b5 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -220,6 +220,7 @@ enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file) ret = enable_kretprobe(&tp->rp); else ret = enable_kprobe(&tp->rp.kp); + WARN_ON(ret); } out: return ret; -- 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/