Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754116AbZDOQWO (ORCPT ); Wed, 15 Apr 2009 12:22:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752688AbZDOQV5 (ORCPT ); Wed, 15 Apr 2009 12:21:57 -0400 Received: from fk-out-0910.google.com ([209.85.128.186]:42616 "EHLO fk-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752582AbZDOQV5 (ORCPT ); Wed, 15 Apr 2009 12:21:57 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=AgHdZH65eafZdLZX74RTBVLHAtddeO6YfxwzIEImrHlRYukvjhpd8xR/sKaFQut2Dz fGBxvaCGLnm7tnBOECag6JMfbG+XU7iTRZSFLAfMICqHo/uTvVpHVu5olPQ3fvfu8Gow 4NiANuUk2EnW4W6n4moGeGb8Y1UMWxOrKRkI4= Date: Wed, 15 Apr 2009 18:21:53 +0200 From: Frederic Weisbecker To: Tom Zanussi Cc: LKML , Ingo Molnar , Steven Rostedt , paulmck@linux.vnet.ibm.com Subject: Re: [PATCH] tracing/filters: allow on-the-fly filter switching Message-ID: <20090415162151.GH5989@nowhere> References: <1239610670.6660.49.camel@tropicana> <20090414205635.GA5968@nowhere> <1239769945.7852.21.camel@tropicana> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1239769945.7852.21.camel@tropicana> 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: 1945 Lines: 77 On Tue, Apr 14, 2009 at 11:32:25PM -0500, Tom Zanussi wrote: > On Tue, 2009-04-14 at 22:56 +0200, Frederic Weisbecker wrote: > > On Mon, Apr 13, 2009 at 03:17:50AM -0500, Tom Zanussi wrote: > > [...] > > > > > > > BTW, this issue might be already present before this patch. > > What happens if: > > > > > > T1 T2 > > > > event_filter_read() { > > filter_print_preds() { > > for (i = 0; i < n_preds; i++) { > > pred = preds[i]; > > event_filter_write() { > > filter_disable_preds(); > > filter_clear_preds() { > > kfree(pred->field_name); > > field_name = pred->field_name; > > // CRASH!!! > > > > > > You need a mutex to protect these two callbacks. > > It would also protect concurrent calls to event_filter_write(), > > which would result in random. > > > > Yeah, Li Zefan had already fixed this, but it wasn't included in this > patch. Looks like he'll be resubmitting that part... > > > > > > > [...] > > > Also, is filter_add_pred() supposed to be available for in-kernel > > uses by other tracers or something? > > No, the current callers were the only ones I'd planned on (it's not > static because code in trace_events.c needs to call it). But, do you > see a use for it by other tracers? May be in the future, it's possible that a tracer might want to set filters by itself. But I don't think it has to be fixed now because there are nothing like that for now. So, no problem :-) Frederic. > > If this is planned, the locking could be even deeper than my comments. > > > > Other than these comments: > > > > Acked-by: Frederic Weisbecker > > > > Thanks! > > > > Thanks for reviewing it! > > Tom > -- 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/