From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A4C0C46464 for ; Thu, 9 Aug 2018 14:17:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4BA3D21E21 for ; Thu, 9 Aug 2018 14:17:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4BA3D21E21 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732190AbeHIQmX (ORCPT ); Thu, 9 Aug 2018 12:42:23 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:39078 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730634AbeHIQmW (ORCPT ); Thu, 9 Aug 2018 12:42:22 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3AE9540216EB; Thu, 9 Aug 2018 14:17:16 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.34.27.30]) by smtp.corp.redhat.com (Postfix) with SMTP id 6A9F710073B4; Thu, 9 Aug 2018 14:17:14 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 9 Aug 2018 16:17:16 +0200 (CEST) Date: Thu, 9 Aug 2018 16:17:13 +0200 From: Oleg Nesterov To: Jiri Olsa Cc: Arnaldo Carvalho de Melo , lkml , Ingo Molnar , Namhyung Kim , David Ahern , Alexander Shishkin , Peter Zijlstra , Milind Chabbi , Frederic Weisbecker Subject: Re: [PATCH 4/5] perf/hw_breakpoint: Set breakpoint as disabled in modify_user_hw_breakpoint error path Message-ID: <20180809141713.GB22636@redhat.com> References: <20180809120305.20693-1-jolsa@kernel.org> <20180809120305.20693-5-jolsa@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180809120305.20693-5-jolsa@kernel.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Thu, 09 Aug 2018 14:17:16 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Thu, 09 Aug 2018 14:17:16 +0000 (UTC) for IP:'10.11.54.3' DOMAIN:'int-mx03.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'oleg@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/09, Jiri Olsa wrote: > > @@ -523,8 +523,10 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att > perf_event_disable(bp); > > err = modify_user_hw_breakpoint_check(bp, attr, false); > - if (err) > + if (err) { > + bp->attr.disabled = 1; > return err; Yes, but on the second thought... Can't we simply do int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr) { int err; /* * modify_user_hw_breakpoint can be invoked with IRQs disabled and hence it * will not be possible to raise IPIs that invoke __perf_event_disable. * So call the function directly after making sure we are targeting the * current task. */ if (irqs_disabled() && bp->ctx && bp->ctx->task == current) perf_event_disable_local(bp); else perf_event_disable(bp); err = modify_user_hw_breakpoint_check(bp, attr, false); if (!bp.attr->disabled) perf_event_enable(bp); return err; } instead of this and the next patch? We can do this because (as you pointed out) validate_hw_breakpoint() has already gone in -tip tree, and (afaics) modify_user_hw_breakpoint_check() never changes perf_event's state on failure, so we can safely "restart" this bp if it was enabled before. 1. This is what we had before the recent f67b15037a7a50c57f72e69a6d59941ad90a0f0f "perf/hwbp: Simplify the perf-hwbp code, fix documentation". Note that this commit was actually the bug fix which introduced another problem fixed by your 2/5. But see above, perf_event_enable() is no longer unsafe after modify_user_hw_breakpoint_check(), we can restore the previous semantics. 2. This matches perf_event_modify_breakpoint(). Which btw can be simplified a bit, it too can simply do if (!bp->attr.disabled) _perf_event_enable(bp); return err; Oleg.