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([2402:f000:1:1501:200:5efe:a66f:8b73]) by smtp.gmail.com with ESMTPSA id c22sm12668511pfo.50.2020.01.13.00.20.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 Jan 2020 00:20:35 -0800 (PST) Subject: Re: [PATCH] ALSA: cmipci: Fix possible a data race in snd_cmipci_interrupt() To: Takashi Iwai Cc: perex@perex.cz, tiwai@suse.com, rfontana@redhat.com, tglx@linutronix.de, allison@lohutok.net, alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org References: <20200111163027.27135-1-baijiaju1990@gmail.com> From: Jia-Ju Bai Message-ID: Date: Mon, 13 Jan 2020 16:20:37 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/1/12 16:20, Takashi Iwai wrote: > On Sat, 11 Jan 2020 17:30:27 +0100, > Jia-Ju Bai wrote: >> The functions snd_cmipci_interrupt() and snd_cmipci_capture_trigger() >> may be concurrently executed. >> >> The function snd_cmipci_capture_trigger() calls >> snd_cmipci_pcm_trigger(). In snd_cmipci_pcm_trigger(), the variable >> rec->running is written with holding a spinlock cm->reg_lock. But in >> snd_cmipci_interrupt(), the identical variable cm->channel[0].running >> or cm->channel[1].running is read without holding this spinlock. Thus, >> a possible data race may occur. >> >> To fix this data race, in snd_cmipci_interrupt(), the variables >> cm->channel[0].running and cm->channel[1].running are read with holding >> the spinlock cm->reg_lock. >> >> This data race is found by the runtime testing of our tool DILP-2. >> >> Signed-off-by: Jia-Ju Bai > Thanks for the patch. > > That's indeed a kind of race, but this change won't fix anything in > practice, though. The inconsistent running flag between those places, > there are two cases: > > - running became 0 to 1; this cannot happen, as the irq isn't issued > before the stream gets started > > - running became 1 to 0; this means that the stream gets stopped > between two points, and it's not better to call > snd_pcm_period_elapsed() for an already stopped stream. Thanks for the reply :) I am not sure to understand your words. Do you mean that this code should be also protected by the spinlock?     if (cm->pcm) {         if ((status & CM_CHINT0) && cm->channel[0].running)             snd_pcm_period_elapsed(cm->channel[0].substream);         if ((status & CM_CHINT1) && cm->channel[1].running)             snd_pcm_period_elapsed(cm->channel[1].substream);     } Best wishes, Jia-Ju Bai 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=-5.0 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED,DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 A46D1C33CAE for ; Mon, 13 Jan 2020 08:21:35 +0000 (UTC) Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) (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 B6573207E0 for ; 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([2402:f000:1:1501:200:5efe:a66f:8b73]) by smtp.gmail.com with ESMTPSA id c22sm12668511pfo.50.2020.01.13.00.20.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 Jan 2020 00:20:35 -0800 (PST) To: Takashi Iwai References: <20200111163027.27135-1-baijiaju1990@gmail.com> From: Jia-Ju Bai Message-ID: Date: Mon, 13 Jan 2020 16:20:37 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US Cc: alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, tiwai@suse.com, rfontana@redhat.com, tglx@linutronix.de, allison@lohutok.net Subject: Re: [alsa-devel] [PATCH] ALSA: cmipci: Fix possible a data race in snd_cmipci_interrupt() X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: base64 Content-Type: text/plain; charset="utf-8"; Format="flowed" Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" CgpPbiAyMDIwLzEvMTIgMTY6MjAsIFRha2FzaGkgSXdhaSB3cm90ZToKPiBPbiBTYXQsIDExIEph biAyMDIwIDE3OjMwOjI3ICswMTAwLAo+IEppYS1KdSBCYWkgd3JvdGU6Cj4+IFRoZSBmdW5jdGlv bnMgc25kX2NtaXBjaV9pbnRlcnJ1cHQoKSBhbmQgc25kX2NtaXBjaV9jYXB0dXJlX3RyaWdnZXIo KQo+PiBtYXkgYmUgY29uY3VycmVudGx5IGV4ZWN1dGVkLgo+Pgo+PiBUaGUgZnVuY3Rpb24gc25k X2NtaXBjaV9jYXB0dXJlX3RyaWdnZXIoKSBjYWxscwo+PiBzbmRfY21pcGNpX3BjbV90cmlnZ2Vy KCkuIEluIHNuZF9jbWlwY2lfcGNtX3RyaWdnZXIoKSwgdGhlIHZhcmlhYmxlCj4+IHJlYy0+cnVu bmluZyBpcyB3cml0dGVuIHdpdGggaG9sZGluZyBhIHNwaW5sb2NrIGNtLT5yZWdfbG9jay4gQnV0 IGluCj4+IHNuZF9jbWlwY2lfaW50ZXJydXB0KCksIHRoZSBpZGVudGljYWwgdmFyaWFibGUgY20t PmNoYW5uZWxbMF0ucnVubmluZwo+PiBvciBjbS0+Y2hhbm5lbFsxXS5ydW5uaW5nIGlzIHJlYWQg d2l0aG91dCBob2xkaW5nIHRoaXMgc3BpbmxvY2suIFRodXMsCj4+IGEgcG9zc2libGUgZGF0YSBy YWNlIG1heSBvY2N1ci4KPj4KPj4gVG8gZml4IHRoaXMgZGF0YSByYWNlLCBpbiBzbmRfY21pcGNp X2ludGVycnVwdCgpLCB0aGUgdmFyaWFibGVzCj4+IGNtLT5jaGFubmVsWzBdLnJ1bm5pbmcgYW5k IGNtLT5jaGFubmVsWzFdLnJ1bm5pbmcgYXJlIHJlYWQgd2l0aCBob2xkaW5nCj4+IHRoZSBzcGlu bG9jayBjbS0+cmVnX2xvY2suCj4+Cj4+IFRoaXMgZGF0YSByYWNlIGlzIGZvdW5kIGJ5IHRoZSBy dW50aW1lIHRlc3Rpbmcgb2Ygb3VyIHRvb2wgRElMUC0yLgo+Pgo+PiBTaWduZWQtb2ZmLWJ5OiBK aWEtSnUgQmFpIDxiYWlqaWFqdTE5OTBAZ21haWwuY29tPgo+IFRoYW5rcyBmb3IgdGhlIHBhdGNo Lgo+Cj4gVGhhdCdzIGluZGVlZCBhIGtpbmQgb2YgcmFjZSwgYnV0IHRoaXMgY2hhbmdlIHdvbid0 IGZpeCBhbnl0aGluZyBpbgo+IHByYWN0aWNlLCB0aG91Z2guICBUaGUgaW5jb25zaXN0ZW50IHJ1 bm5pbmcgZmxhZyBiZXR3ZWVuIHRob3NlIHBsYWNlcywKPiB0aGVyZSBhcmUgdHdvIGNhc2VzOgo+ Cj4gLSBydW5uaW5nIGJlY2FtZSAwIHRvIDE7IHRoaXMgY2Fubm90IGhhcHBlbiwgYXMgdGhlIGly cSBpc24ndCBpc3N1ZWQKPiAgICBiZWZvcmUgdGhlIHN0cmVhbSBnZXRzIHN0YXJ0ZWQKPgo+IC0g cnVubmluZyBiZWNhbWUgMSB0byAwOyB0aGlzIG1lYW5zIHRoYXQgdGhlIHN0cmVhbSBnZXRzIHN0 b3BwZWQKPiAgICBiZXR3ZWVuIHR3byBwb2ludHMsIGFuZCBpdCdzIG5vdCBiZXR0ZXIgdG8gY2Fs bAo+ICAgIHNuZF9wY21fcGVyaW9kX2VsYXBzZWQoKSBmb3IgYW4gYWxyZWFkeSBzdG9wcGVkIHN0 cmVhbS4KClRoYW5rcyBmb3IgdGhlIHJlcGx5IDopCgpJIGFtIG5vdCBzdXJlIHRvIHVuZGVyc3Rh bmQgeW91ciB3b3Jkcy4KCkRvIHlvdSBtZWFuIHRoYXQgdGhpcyBjb2RlIHNob3VsZCBiZSBhbHNv IHByb3RlY3RlZCBieSB0aGUgc3BpbmxvY2s/CiDCoMKgwqAgaWYgKGNtLT5wY20pIHsKIMKgwqDC oCDCoMKgwqAgaWYgKChzdGF0dXMgJiBDTV9DSElOVDApICYmIGNtLT5jaGFubmVsWzBdLnJ1bm5p bmcpCiDCoMKgwqAgwqDCoMKgIMKgwqDCoCBzbmRfcGNtX3BlcmlvZF9lbGFwc2VkKGNtLT5jaGFu bmVsWzBdLnN1YnN0cmVhbSk7CiDCoMKgwqAgwqDCoMKgIGlmICgoc3RhdHVzICYgQ01fQ0hJTlQx KSAmJiBjbS0+Y2hhbm5lbFsxXS5ydW5uaW5nKQogwqDCoMKgIMKgwqDCoCDCoMKgwqAgc25kX3Bj bV9wZXJpb2RfZWxhcHNlZChjbS0+Y2hhbm5lbFsxXS5zdWJzdHJlYW0pOwogwqDCoMKgIH0KCgpC ZXN0IHdpc2hlcywKSmlhLUp1IEJhaQpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fXwpBbHNhLWRldmVsIG1haWxpbmcgbGlzdApBbHNhLWRldmVsQGFsc2EtcHJv amVjdC5vcmcKaHR0cHM6Ly9tYWlsbWFuLmFsc2EtcHJvamVjdC5vcmcvbWFpbG1hbi9saXN0aW5m by9hbHNhLWRldmVsCg==