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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BEBEAEB64DA for ; Mon, 26 Jun 2023 11:13:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230164AbjFZLN1 (ORCPT ); Mon, 26 Jun 2023 07:13:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52264 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229761AbjFZLN0 (ORCPT ); Mon, 26 Jun 2023 07:13:26 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0099ECE for ; Mon, 26 Jun 2023 04:13:24 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id ACC391F8AB; Mon, 26 Jun 2023 11:13:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1687778003; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=vKaUDMX7q/k4wnF5zn+Vr6K9ID3Iq87i7XrGFy/yZkk=; b=xDSvj+cA2CrQW1d62/Hj9ME9axiJ+O/23UMa+mgChTWNbHzBw4uM/vWi5T1dR2joITeEOE H3MVyOpfp1IeqA5cjVs3PZ79QjwUlCIzZ5M5oLdtunX6FHbqJHZUXQPVLgQQmNO0rZYtna VyTxkWulNw7C7ahnlnVhHJzmMyPOHiQ= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1687778003; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=vKaUDMX7q/k4wnF5zn+Vr6K9ID3Iq87i7XrGFy/yZkk=; b=MTQZUZ7DNlmCoXdgQk6JahE7IEQ55oYgyNPsqB40wbT1iqRA8yXqESqu/5jzwapNseMsTk UC6JtrgSrpqJw0Cw== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 7F3FF13483; Mon, 26 Jun 2023 11:13:23 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id RToNHtNymWT4JAAAMHmgww (envelope-from ); Mon, 26 Jun 2023 11:13:23 +0000 Date: Mon, 26 Jun 2023 13:13:21 +0200 Message-ID: <87ttuuv5m6.wl-tiwai@suse.de> From: Takashi Iwai To: Jaroslav Kysela Cc: Tuo Li , tiwai@suse.com, alsa-devel@alsa-project.org, Linux Kernel , baijiaju1990@outlook.com Subject: Re: [BUG] ALSA: core: pcm_memory: a possible data race in do_alloc_pages() In-Reply-To: <45445f57-0a73-59e6-6f3d-3983ce93a324@perex.cz> References: <877crqwvi1.wl-tiwai@suse.de> <871qhywucj.wl-tiwai@suse.de> <4d0931bf-b356-6969-5aaf-b663d7f2b21a@perex.cz> <87wmzqv64o.wl-tiwai@suse.de> <45445f57-0a73-59e6-6f3d-3983ce93a324@perex.cz> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.2 Mule/6.0 MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 26 Jun 2023 13:09:00 +0200, Jaroslav Kysela wrote: > > On 26. 06. 23 13:02, Takashi Iwai wrote: > > On Mon, 26 Jun 2023 09:56:47 +0200, > > Jaroslav Kysela wrote: > >> > >> On 26. 06. 23 9:33, Takashi Iwai wrote: > >>> On Mon, 26 Jun 2023 09:31:18 +0200, > >>> Tuo Li wrote: > >>>> > >>>> > >>>> Hello, > >>>> > >>>> Thank you for your reply! > >>> > >>> FWIW, the simplest fix would be something like below, just extending > >>> the mutex coverage. But it'll serialize the all calls, so it might > >>> influence on the performance, while it's the safest way. > >> > >> It may be better to update total_pcm_alloc_bytes before > >> snd_dma_alloc_dir_pages() call and decrease this value when allocation > >> fails to allow parallel allocations. Then the mutex can be held only > >> for the total_pcm_alloc_bytes variable update. > > > > Yes, it'd work. But a tricky part is that the actual allocation size > > can be bigger, and we need to correct the total_pcm_alloc_bytes after > > the allocation result. So the end result would be a patch like below, > > which is a bit more complex than the previous simpler approach. But > > it might be OK. > > The patch looks good, but it may be better to move the "post" variable > updates to an inline function (mutex lock - update - mutex unlock) for > a better readability. Sounds like a good idea. Let me cook later. Takashi