From patchwork Mon Jul 27 06:07:28 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sai Prakash Ranjan X-Patchwork-Id: 11686365 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C5F1E1392 for ; Mon, 27 Jul 2020 06:08:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AB2372075D for ; Mon, 27 Jul 2020 06:08:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="axsPb4vl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726410AbgG0GIH (ORCPT ); Mon, 27 Jul 2020 02:08:07 -0400 Received: from mail29.static.mailgun.info ([104.130.122.29]:17277 "EHLO mail29.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726124AbgG0GIH (ORCPT ); Mon, 27 Jul 2020 02:08:07 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1595830086; h=Content-Transfer-Encoding: MIME-Version: Message-Id: Date: Subject: Cc: To: From: Sender; bh=SdcmaivCbgx/EWFdy+61EjwpmapmcsR2LcYkxL9I74c=; b=axsPb4vlVrvj4twunuEeWueX+LxWA+eBdV8MLnCIVx+UwJpINSxcueNRcaWAfiWXoUW1gu+q wDb0ZFDOM6S7jc+0PvtBhlgYWJXcqY315HGQzqIl9w6WDvMTx8smKiO/MfXp+0S38MBxNeqV pu7tPeRuRgPeCYcm5HCcOu3TLAk= X-Mailgun-Sending-Ip: 104.130.122.29 X-Mailgun-Sid: WyI1MzIzYiIsICJsaW51eC1hcm0tbXNtQHZnZXIua2VybmVsLm9yZyIsICJiZTllNGEiXQ== Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n01.prod.us-west-2.postgun.com with SMTP id 5f1e6f31ca57a65d473553fb (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Mon, 27 Jul 2020 06:07:45 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id DD741C433A0; Mon, 27 Jul 2020 06:07:44 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-caf-mail-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=2.0 tests=ALL_TRUSTED,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.0 Received: from blr-ubuntu-253.qualcomm.com (blr-bdr-fw-01_GlobalNAT_AllZones-Outside.qualcomm.com [103.229.18.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: saiprakash.ranjan) by smtp.codeaurora.org (Postfix) with ESMTPSA id 8BE03C433CB; Mon, 27 Jul 2020 06:07:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 8BE03C433CB Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=saiprakash.ranjan@codeaurora.org From: Sai Prakash Ranjan To: Mathieu Poirier , Suzuki K Poulose , Mike Leach Cc: linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, Stephen Boyd , linux-kernel@vger.kernel.org, coresight@lists.linaro.org, Sai Prakash Ranjan Subject: [PATCH] coresight: etm4x: Fix etm4_count race using atomic variable Date: Mon, 27 Jul 2020 11:37:28 +0530 Message-Id: <20200727060728.15027-1-saiprakash.ranjan@codeaurora.org> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org etm4_count keeps track of number of ETMv4 registered and on some systems, a race is observed on etm4_count variable which can lead to multiple calls to cpuhp_setup_state_nocalls_cpuslocked(). This function internally calls cpuhp_store_callbacks() which prevents multiple registrations of callbacks for a given state and due to this race, it returns -EBUSY leading to ETM probe failures like below. coresight-etm4x: probe of 7040000.etm failed with error -16 This race can easily be triggered with async probe by setting probe type as PROBE_PREFER_ASYNCHRONOUS and with ETM power management property "arm,coresight-loses-context-with-cpu". Prevent this race by converting etm4_count variable to atomic. Fixes: 9b6a3f3633a5 ("coresight: etmv4: Fix CPU power management setup in probe() function") Fixes: 58eb457be028 ("hwtracing/coresight-etm4x: Convert to hotplug state machine") Suggested-by: Mike Leach (Mike: Rootcause and context for commit message) Signed-off-by: Sai Prakash Ranjan --- drivers/hwtracing/coresight/coresight-etm4x.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c index 6d7d2169bfb2..f256ea744c51 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x.c +++ b/drivers/hwtracing/coresight/coresight-etm4x.c @@ -49,7 +49,7 @@ MODULE_PARM_DESC(pm_save_enable, "Save/restore state on power down: 1 = never, 2 = self-hosted"); /* The number of ETMv4 currently registered */ -static int etm4_count; +static atomic_t etm4_count; static struct etmv4_drvdata *etmdrvdata[NR_CPUS]; static void etm4_set_default_config(struct etmv4_config *config); static int etm4_set_event_filters(struct etmv4_drvdata *drvdata, @@ -1403,7 +1403,7 @@ static int etm4_pm_setup_cpuslocked(void) { int ret; - if (etm4_count++) + if (atomic_inc_return(&etm4_count)) return 0; ret = cpu_pm_register_notifier(&etm4_cpu_pm_nb); @@ -1434,13 +1434,13 @@ static int etm4_pm_setup_cpuslocked(void) cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); reduce_count: - --etm4_count; + atomic_dec(&etm4_count); return ret; } static void etm4_pm_clear(void) { - if (--etm4_count != 0) + if (atomic_dec_return(&etm4_count) != 0) return; cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);