From patchwork Wed Apr 26 06:20:23 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tze-nan Wu X-Patchwork-Id: 13224151 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 86794C77B60 for ; Wed, 26 Apr 2023 06:31:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:MIME-Version: Message-ID:Date:Subject:CC:To:From:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Owner; bh=WU3jPIGaeYnCfh0tvdyVkWtQSLr3g7psnjDX46eOhxg=; b=Hk0IenD6fldnI4lGx/mB4DGZl0 mysg08+7rm9Z2zWXIbVk+HZKN52HemptwZzOh0rCYHcrI2OfErOIAxCaa81I9S2rOR6NHGsS9HcmR tza/nKrq+8SO2uq2c/Bpu9Ri0OYUEz94gbAwtHe638qwinX9rlkEc6zTK6J6tL1djZ1HJ4L4WNqxp 7ufdrFvV2Yvs7i/MdfHwHcK6v2vncnCOaiH+vRE+IP/tVI1BXNjfzYb1C4Snm1jekOsdxpKvcjple 3IQB1MflhNTXMTGUhRf/qgQQxdq+cR7w7f/4P27+Je/Y3EoVNxjdXEtQw3CBuWzC/n4hHeHOjo459 WpVqQ/RA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1prYfz-002wos-05; Wed, 26 Apr 2023 06:30:51 +0000 Received: from mailgw02.mediatek.com ([216.200.240.185]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1prYfw-002woN-0c; Wed, 26 Apr 2023 06:30:49 +0000 X-UUID: df57fa18e3fb11ed8687db9d93187ff1-20230425 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mediatek.com; s=dk; h=Content-Type:MIME-Version:Message-ID:Date:Subject:CC:To:From; bh=WU3jPIGaeYnCfh0tvdyVkWtQSLr3g7psnjDX46eOhxg=; b=GbSKqM7x6+AvT1faNKgkL/vxN79EpESReJMJScfZ1Fi83aDgJyGcIKP9mcWtbX4+wdVx9aVQ6CKdt23ZjxzKZGnLA5+MCCIFaLT3rtOhB1O3t9FokLGlUczzmqN4lau13DqqfkBePuZK6dX9Q+OktK6+2jkg0lGZUwtKvpv2D1c=; X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.22,REQID:b5fd70a2-c4f9-4f34-b79e-4befb540deaa,IP:0,U RL:0,TC:0,Content:-25,EDM:0,RT:0,SF:0,FILE:0,BULK:0,RULE:Release_Ham,ACTIO N:release,TS:-25 X-CID-META: VersionHash:120426c,CLOUDID:b3154885-cd9c-45f5-8134-710979e3df0e,B ulkID:nil,BulkQuantity:0,Recheck:0,SF:102,TC:nil,Content:0,EDM:-3,IP:nil,U RL:11|1,File:nil,Bulk:nil,QS:nil,BEC:nil,COL:0,OSI:0,OSA:0,AV:0 X-CID-BVR: 0 X-CID-BAS: 0,_,0,_ X-UUID: df57fa18e3fb11ed8687db9d93187ff1-20230425 Received: from mtkmbs11n1.mediatek.inc [(172.21.101.185)] by mailgw02.mediatek.com (envelope-from ) (musrelay.mediatek.com ESMTP with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 1388802250; Tue, 25 Apr 2023 23:30:44 -0700 Received: from mtkmbs13n2.mediatek.inc (172.21.101.108) by mtkmbs10n2.mediatek.inc (172.21.101.183) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.26; Wed, 26 Apr 2023 14:20:41 +0800 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkmbs13n2.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.2.1118.26 via Frontend Transport; Wed, 26 Apr 2023 14:20:41 +0800 From: Tze-nan Wu To: , CC: , , , Tze-nan Wu , , , AngeloGioacchino Del Regno , "Paul E. McKenney" , , , , Subject: [PATCH v5] ring-buffer: Ensure proper resetting of atomic variables in ring_buffer_reset_online_cpus Date: Wed, 26 Apr 2023 14:20:23 +0800 Message-ID: <20230426062027.17451-1-Tze-nan.Wu@mediatek.com> X-Mailer: git-send-email 2.18.0 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230425_233048_240382_6ABCD88D X-CRM114-Status: GOOD ( 14.18 ) X-BeenThere: linux-mediatek@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org In ring_buffer_reset_online_cpus, the buffer_size_kb write operation may permanently fail if the cpu_online_mask changes between two for_each_online_buffer_cpu loops. The number of increases and decreases on both cpu_buffer->resize_disabled and cpu_buffer->record_disabled may be inconsistent, causing some CPUs to have non-zero values for these atomic variables after the function returns. This issue can be reproduced by "echo 0 > trace" while hotplugging cpu. After reproducing success, we can find out buffer_size_kb will not be functional anymore. To prevent leaving 'resize_disabled' and 'record_disabled' non-zero after ring_buffer_reset_online_cpus returns, we ensure that each atomic variable has been set up before atomic_sub() to it. Cc: stable@vger.kernel.org Cc: npiggin@gmail.com Fixes: b23d7a5f4a07 ("ring-buffer: speed up buffer resets by avoiding synchronize_rcu for each CPU") Reviewed-by: Cheng-Jui Wang Signed-off-by: Tze-nan Wu --- Changes from v4 to v5: https://lore.kernel.org/lkml/20230412112401.25081-1-Tze-nan.Wu@mediatek.com/ - Move the define before the function --- kernel/trace/ring_buffer.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 76a2d91eecad..253ef85a9ec3 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -5345,6 +5345,9 @@ void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu) } EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu); +/* Flag to ensure proper resetting of atomic variables */ +#define RESET_BIT (1 << 30) + /** * ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer * @buffer: The ring buffer to reset a per cpu buffer of @@ -5361,20 +5364,27 @@ void ring_buffer_reset_online_cpus(struct trace_buffer *buffer) for_each_online_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; - atomic_inc(&cpu_buffer->resize_disabled); + atomic_add(RESET_BIT, &cpu_buffer->resize_disabled); atomic_inc(&cpu_buffer->record_disabled); } /* Make sure all commits have finished */ synchronize_rcu(); - for_each_online_buffer_cpu(buffer, cpu) { + for_each_buffer_cpu(buffer, cpu) { cpu_buffer = buffer->buffers[cpu]; + /* + * If a CPU came online during the synchronize_rcu(), then + * ignore it. + */ + if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT)) + continue; + reset_disabled_cpu_buffer(cpu_buffer); atomic_dec(&cpu_buffer->record_disabled); - atomic_dec(&cpu_buffer->resize_disabled); + atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled); } mutex_unlock(&buffer->mutex);