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 60474EB64D7 for ; Mon, 26 Jun 2023 13:37:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230016AbjFZNhm (ORCPT ); Mon, 26 Jun 2023 09:37:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43454 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229821AbjFZNhk (ORCPT ); Mon, 26 Jun 2023 09:37:40 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0F14FB1 for ; Mon, 26 Jun 2023 06:37:38 -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-out1.suse.de (Postfix) with ESMTPS id A912221867; Mon, 26 Jun 2023 13:37:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1687786657; 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=jUBjTAufjEln2vbph+DCrSwWVeakUOgT748UPyQBH7M=; b=Y3YnlDlewui2Sb35svlBgg7ORuRA3ZV7JeBHNwi5NMNYO9HUhl3hCvL3UN0fyHsU3Vr8YE KA4SHIzscegqf3Rj5oHx8jRluTevvWccvWTxoiAYI/XlylKkrJs+2Y5zxoKVe+j10dPneM 0HDFSkY6im9coOSsbsKHnz48ZHlIsac= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1687786657; 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=jUBjTAufjEln2vbph+DCrSwWVeakUOgT748UPyQBH7M=; b=QeZ8uo/1BufTlRiSiyzrtNc7gPHInwJdTcNbeccLQoCtWnqlp/J5dA0bH2BWeFT3BEgzdR nSaq7Tw9qHpXz4CA== 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 7D7E413483; Mon, 26 Jun 2023 13:37:37 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id X+K4HaGUmWTzawAAMHmgww (envelope-from ); Mon, 26 Jun 2023 13:37:37 +0000 Date: Mon, 26 Jun 2023 15:37:36 +0200 Message-ID: <87bkh2uyxr.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: 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> <87ttuuv5m6.wl-tiwai@suse.de> <87jzvquzyr.wl-tiwai@suse.de> 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 15:32:40 +0200, Jaroslav Kysela wrote: > > On 26. 06. 23 15:15, Takashi Iwai wrote: > > On Mon, 26 Jun 2023 13:13:21 +0200, > > Takashi Iwai wrote: > >> > >> 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. > > > > ... and here it is. > > > > If that looks OK, I'll submit a proper fix patch. > > > > > > thanks, > > > > Takashi > > > > --- a/sound/core/pcm_memory.c > > +++ b/sound/core/pcm_memory.c > > @@ -31,15 +31,41 @@ static unsigned long max_alloc_per_card = 32UL * 1024UL * 1024UL; > > module_param(max_alloc_per_card, ulong, 0644); > > MODULE_PARM_DESC(max_alloc_per_card, "Max total allocation bytes per card."); > > +static void __update_allocated_size(struct snd_card *card, > > ssize_t bytes) > > Missing inline ? May be also used for > > > +static void update_allocated_size(struct snd_card *card, ssize_t bytes) > > +static void decrease_allocated_size(struct snd_card *card, size_t bytes) I left the optimizations to compilers. Usually they do inline if it makes sense, and it's often a more sensible choice. thanks, Takashi