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=-10.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 947E3C433DF for ; Mon, 27 Jul 2020 08:57:39 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5F3632072E for ; Mon, 27 Jul 2020 08:57:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="PCez/jxx"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="hGCkmbbk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5F3632072E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Message-ID:References:In-Reply-To:Subject:To:From: Date:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=2m7gQLBnPevUG6r9OmObxscjRh6AmM3/xiTwuXdPdVo=; b=PCez/jxx4kvgmr21DqVPKq494 BzIGE3GCy3kau5+EDRRUlrCjF2TinPWTWi7tS96x6Ffezf/KEpiqil2nJvDhAVAZJIoHfFcsPLcMC 2GjmGyaIqj3c0vFTgg7T/CckP55Pi1eJ0EWajfd9IPWA98Xbadh0qzC+ZIcZyUTWiVEZhPs+hbTpu AAAP6Tg4wXDR+MNnMR7JzlE+/WSDdDQmhfV+UP3W6rhoCVun3oLoB8nb06tsF+B1T2b+Uwa76nLC6 XxJ4vt7v9/QmQ8FrS51BA0JL3bhyj49Z3JvimgyAc37ddZ/8DjOdrSsXqLlnkG+1bfMWEzTUJ6MrW 49TDN4y5g==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jzyvd-0003ai-IO; Mon, 27 Jul 2020 08:56:13 +0000 Received: from mail29.static.mailgun.info ([104.130.122.29]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jzyva-0003aC-1H for linux-arm-kernel@lists.infradead.org; Mon, 27 Jul 2020 08:56:12 +0000 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1595840171; h=Message-ID: References: In-Reply-To: Subject: Cc: To: From: Date: Content-Transfer-Encoding: Content-Type: MIME-Version: Sender; bh=xPmKjdUK0acJr1A0bQShRP8M7cHV9/zPMfSfRXx1CNA=; b=hGCkmbbkGrCmE+dBMNzcoic8x205e9ED6wj5WbQd/TpBJpkG+Cuvn0cZUGQL4sDegkPpivCJ UEoc8xdDqHl4AjOfyEcqe0j/wxm+c3lJLX0jnGZUwmHFJB0i6NxW3w+NjVYX7P49v7GpJkTI e3c6S5MSmyDaxI9sPmGzaaUaStI= X-Mailgun-Sending-Ip: 104.130.122.29 X-Mailgun-Sid: WyJiYzAxZiIsICJsaW51eC1hcm0ta2VybmVsQGxpc3RzLmluZnJhZGVhZC5vcmciLCAiYmU5ZTRhIl0= Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n04.prod.us-west-2.postgun.com with SMTP id 5f1e96a1634c4259e309c1d1 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Mon, 27 Jul 2020 08:56:01 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id B72B4C43391; Mon, 27 Jul 2020 08:56:01 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: saiprakash.ranjan) by smtp.codeaurora.org (Postfix) with ESMTPSA id 0AEF0C433C9; Mon, 27 Jul 2020 08:56:01 +0000 (UTC) MIME-Version: 1.0 Date: Mon, 27 Jul 2020 14:26:00 +0530 From: Sai Prakash Ranjan To: Mathieu Poirier , Suzuki K Poulose , Mike Leach Subject: Re: [PATCH] coresight: etm4x: Fix etm4_count race using atomic variable In-Reply-To: <20200727060728.15027-1-saiprakash.ranjan@codeaurora.org> References: <20200727060728.15027-1-saiprakash.ranjan@codeaurora.org> Message-ID: <0541ded117bb2a63481de8c015282b11@codeaurora.org> X-Sender: saiprakash.ranjan@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200727_045611_641087_4EA7A07F X-CRM114-Status: GOOD ( 21.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arm-msm@vger.kernel.org, coresight@lists.linaro.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Stephen Boyd Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2020-07-27 11:37, Sai Prakash Ranjan wrote: > 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; > Sorry, I messed up here, will send a next version fixing this. Thanks, Sai -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel