From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 92238130AC8 for ; Tue, 23 Jul 2024 07:02:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.130 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721718134; cv=none; b=ERzJhGUU1J6dWtuau6cuSVWeF/a8qr+I4n1NB5mtmei8ROkTec/qIgLGAwhIUVdjPspdqQ5HNgQ4+eIt22DFveqeitPK5s71iFby6oNrsA8kTOKJfaz+3k2ivTOCZzf8GTP0XY/npFK3qbWD+tiNVKRbSZsEuhAs8BH0dKItPwM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721718134; c=relaxed/simple; bh=WlRZwKDKcA1kmOREZOfWzbRccX+E5enM/6D1oxmQFPc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=AyogpyPUUeA6apjY7cY8shk6vHGG5SjyJLt3XCLYqxIBFT1em+mCRR/DKFyUjTP438qy4L6bYUwD+1jaAEIbr7XumGnxga7w4oyTOZBfrNM8Nuu0NbAnWj1Fthghn3NHuM05kWfCcYSCM089HWWIZRdKANrKF+b69MhE9sdNvCg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz; spf=pass smtp.mailfrom=suse.cz; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=NsVKWqXR; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=GTWkUb0u; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=NsVKWqXR; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=GTWkUb0u; arc=none smtp.client-ip=195.135.223.130 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.cz Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="NsVKWqXR"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="GTWkUb0u"; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="NsVKWqXR"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="GTWkUb0u" Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id B2B4D2174A; Tue, 23 Jul 2024 07:02:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1721718130; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=ah17SItxJ57HnquFDgj7w7ZLVAS8JHQip51CdTKeOak=; b=NsVKWqXRoVR9tG/juxXoxo/sqNBI2/BsioRgLck3mamDhVAdaw6LG4o2cQLEMS11pzTUmJ ixKwNLN2+NKjt31umPb1o+VvgQXfuqoptahg4MsJ3qiq5+6fFrF3oF4n0v3uvmal6I3yO3 XmvrbLH+x2+eSmFN/Itg+9ySvPu4UpA= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1721718130; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=ah17SItxJ57HnquFDgj7w7ZLVAS8JHQip51CdTKeOak=; b=GTWkUb0uMnqcs33QMu9/yXt5nv0QY/1TafxmshsWXb6Ev06jUnCUDghqa5MKvCyUspGI18 jxvaAYroUg9dvfAg== Authentication-Results: smtp-out1.suse.de; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=NsVKWqXR; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=GTWkUb0u DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1721718130; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=ah17SItxJ57HnquFDgj7w7ZLVAS8JHQip51CdTKeOak=; b=NsVKWqXRoVR9tG/juxXoxo/sqNBI2/BsioRgLck3mamDhVAdaw6LG4o2cQLEMS11pzTUmJ ixKwNLN2+NKjt31umPb1o+VvgQXfuqoptahg4MsJ3qiq5+6fFrF3oF4n0v3uvmal6I3yO3 XmvrbLH+x2+eSmFN/Itg+9ySvPu4UpA= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1721718130; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=ah17SItxJ57HnquFDgj7w7ZLVAS8JHQip51CdTKeOak=; b=GTWkUb0uMnqcs33QMu9/yXt5nv0QY/1TafxmshsWXb6Ev06jUnCUDghqa5MKvCyUspGI18 jxvaAYroUg9dvfAg== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 9EA1413874; Tue, 23 Jul 2024 07:02:10 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 2zlnJnJVn2b4TQAAD6G6ig (envelope-from ); Tue, 23 Jul 2024 07:02:10 +0000 Message-ID: <2c81bdc0-8ff3-467d-9ff8-2e7b95bff2af@suse.cz> Date: Tue, 23 Jul 2024 09:02:10 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/page_alloc: Fix pcp->count race between drain_pages_zone() vs __rmqueue_pcplist() To: Li Zhijian , linux-mm@kvack.org Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Yasunori Gotou , David Hildenbrand , Yao Xingtao References: <20240723064428.1179519-1-lizhijian@fujitsu.com> Content-Language: en-US From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: <20240723064428.1179519-1-lizhijian@fujitsu.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Score: -1.30 X-Spam-Flag: NO X-Spamd-Result: default: False [-1.30 / 50.00]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; XM_UA_NO_VERSION(0.01)[]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; RCPT_COUNT_SEVEN(0.00)[7]; RCVD_VIA_SMTP_AUTH(0.00)[]; DWL_DNSWL_BLOCKED(0.00)[suse.cz:dkim]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[fujitsu.com:email]; RCVD_COUNT_TWO(0.00)[2]; DKIM_TRACE(0.00)[suse.cz:+] X-Rspamd-Action: no action X-Spam-Level: X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Queue-Id: B2B4D2174A On 7/23/24 8:44 AM, Li Zhijian wrote: > It's expected that no page should be left in pcp_list after calling > zone_pcp_disable() in offline_pages(). Previously, it's observed that > offline_pages() gets stuck [1] due to some pages remaining in pcp_list. > > Cause: > There is a race condition between drain_pages_zone() and __rmqueue_pcplist() > involving the pcp->count variable. See below scenario: > > CPU0 CPU1 > ---------------- --------------- > spin_lock(&pcp->lock); > __rmqueue_pcplist() { > zone_pcp_disable() { > /* list is empty */ > if (list_empty(list)) { > /* add pages to pcp_list */ > alloced = rmqueue_bulk() > mutex_lock(&pcp_batch_high_lock) > ... > __drain_all_pages() { > drain_pages_zone() { > /* read pcp->count, it's 0 here */ > count = READ_ONCE(pcp->count) > /* 0 means nothing to drain */ > /* update pcp->count */ > pcp->count += alloced << order; > ... > ... > spin_unlock(&pcp->lock); > > In this case, after calling zone_pcp_disable() though, there are still some > pages in pcp_list. And these pages in pcp_list are neither movable nor > isolated, offline_pages() gets stuck as a result. > > Solution: > Expand the scope of the pcp->lock to also protect pcp->count in > drain_pages_zone(), to ensure no pages are left in the pcp list after > zone_pcp_disable() > > [1] https://lore.kernel.org/linux-mm/6a07125f-e720-404c-b2f9-e55f3f166e85@fujitsu.com/ > > Cc: David Hildenbrand > Cc: Vlastimil Babka (SUSE) > Reported-by: Yao Xingtao > Signed-off-by: Li Zhijian Fixes: 4b23a68f9536 ("mm/page_alloc: protect PCP lists with a spinlock") I'd also add a Cc: stable in this case Reviewed-by: Vlastimil Babka Thanks! > --- > V3: > Read pcp->count in the loop with lock held to prevent unnecessary spin_lock() wasteful > V2: > - Narrow down the scope of the spin_lock() to limit the draining latency. # Vlastimil and David > - In above scenario, it's sufficient to read pcp->count once with lock held, and it fully fixed > my issue[1] in thounds runs(It happened in more than 5% before). > RFC: > https://lore.kernel.org/linux-mm/20240716073929.843277-1-lizhijian@fujitsu.com/ > Signed-off-by: Li Zhijian > --- > mm/page_alloc.c | 18 +++++++++++------- > 1 file changed, 11 insertions(+), 7 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 9ecf99190ea2..a32289ec4768 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2323,16 +2323,20 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp) > static void drain_pages_zone(unsigned int cpu, struct zone *zone) > { > struct per_cpu_pages *pcp = per_cpu_ptr(zone->per_cpu_pageset, cpu); > - int count = READ_ONCE(pcp->count); > - > - while (count) { > - int to_drain = min(count, pcp->batch << CONFIG_PCP_BATCH_SCALE_MAX); > - count -= to_drain; > + int count; > > + do { > spin_lock(&pcp->lock); > - free_pcppages_bulk(zone, to_drain, pcp, 0); > + count = pcp->count; > + if (count) { > + int to_drain = min(count, > + pcp->batch << CONFIG_PCP_BATCH_SCALE_MAX); > + > + free_pcppages_bulk(zone, to_drain, pcp, 0); > + count -= to_drain; > + } > spin_unlock(&pcp->lock); > - } > + } while (count); > } > > /*