From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6A0571F946 for ; Fri, 21 Jul 2023 16:24:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E0A8FC433C9; Fri, 21 Jul 2023 16:24:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1689956669; bh=/3SoltwMI42/XF05RtByg7qawtRF9zbf4jhmkfdSWeA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eNFdb/QQ+eZQ1Zk3XGwWMYU4ejCum/BzASKBn613BL/WBTbMyDEllnP9shlYm8bnH +alaiEMKb+USrwHB+2AEn0w8JDqQwNcWmfeMdLCptoaSJtAcOsgvblYi3EQuCTaMY3 q4llwMub2CDF0QdLqsWRpitd+egluS+cWGtXYr24= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Greg Thelen , Namhyung Kim , "Peter Zijlstra (Intel)" Subject: [PATCH 6.4 250/292] perf/x86: Fix lockdep warning in for_each_sibling_event() on SPR Date: Fri, 21 Jul 2023 18:05:59 +0200 Message-ID: <20230721160539.657762091@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230721160528.800311148@linuxfoundation.org> References: <20230721160528.800311148@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Namhyung Kim commit 27c68c216ee1f1b086e789a64486e6511e380b8a upstream. On SPR, the load latency event needs an auxiliary event in the same group to work properly. There's a check in intel_pmu_hw_config() for this to iterate sibling events and find a mem-loads-aux event. The for_each_sibling_event() has a lockdep assert to make sure if it disabled hardirq or hold leader->ctx->mutex. This works well if the given event has a separate leader event since perf_try_init_event() grabs the leader->ctx->mutex to protect the sibling list. But it can cause a problem when the event itself is a leader since the event is not initialized yet and there's no ctx for the event. Actually I got a lockdep warning when I run the below command on SPR, but I guess it could be a NULL pointer dereference. $ perf record -d -e cpu/mem-loads/uP true The code path to the warning is: sys_perf_event_open() perf_event_alloc() perf_init_event() perf_try_init_event() x86_pmu_event_init() hsw_hw_config() intel_pmu_hw_config() for_each_sibling_event() lockdep_assert_event_ctx() We don't need for_each_sibling_event() when it's a standalone event. Let's return the error code directly. Fixes: f3c0eba28704 ("perf: Add a few assertions") Reported-by: Greg Thelen Signed-off-by: Namhyung Kim Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20230704181516.3293665-1-namhyung@kernel.org Signed-off-by: Greg Kroah-Hartman --- arch/x86/events/intel/core.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -3993,6 +3993,13 @@ static int intel_pmu_hw_config(struct pe struct perf_event *leader = event->group_leader; struct perf_event *sibling = NULL; + /* + * When this memload event is also the first event (no group + * exists yet), then there is no aux event before it. + */ + if (leader == event) + return -ENODATA; + if (!is_mem_loads_aux_event(leader)) { for_each_sibling_event(sibling, leader) { if (is_mem_loads_aux_event(sibling))