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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=ham 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 14B62C433E0 for ; Thu, 11 Mar 2021 10:10:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CB72C64DDA for ; Thu, 11 Mar 2021 10:10:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232108AbhCKKKE convert rfc822-to-8bit (ORCPT ); Thu, 11 Mar 2021 05:10:04 -0500 Received: from mslow2.mail.gandi.net ([217.70.178.242]:44591 "EHLO mslow2.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231639AbhCKKJ5 (ORCPT ); Thu, 11 Mar 2021 05:09:57 -0500 Received: from relay13.mail.gandi.net (unknown [217.70.178.233]) by mslow2.mail.gandi.net (Postfix) with ESMTP id A6C273A39D0 for ; Thu, 11 Mar 2021 09:51:22 +0000 (UTC) Received: from xps13 (lfbn-tou-1-1325-59.w90-89.abo.wanadoo.fr [90.89.138.59]) (Authenticated sender: miquel.raynal@bootlin.com) by relay13.mail.gandi.net (Postfix) with ESMTPSA id 6CEA98000D; Thu, 11 Mar 2021 09:50:56 +0000 (UTC) Date: Thu, 11 Mar 2021 10:50:55 +0100 From: Miquel Raynal To: John Ogness Cc: Petr Mladek , Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, Richard Weinberger , Vignesh Raghavendra , linux-mtd@lists.infradead.org Subject: Re: [PATCH next v4 02/15] mtd: mtdoops: synchronize kmsg_dumper Message-ID: <20210311105055.4a0e864d@xps13> In-Reply-To: <20210303101528.29901-3-john.ogness@linutronix.de> References: <20210303101528.29901-1-john.ogness@linutronix.de> <20210303101528.29901-3-john.ogness@linutronix.de> Organization: Bootlin X-Mailer: Claws Mail 3.17.7 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, John Ogness wrote on Wed, 3 Mar 2021 11:15:15 +0100: > The kmsg_dumper can be called from any context and CPU, possibly > from multiple CPUs simultaneously. Since the writing of the buffer > can occur from a later scheduled work queue, the oops buffer must > be protected against simultaneous dumping. > > Use an atomic bit to mark when the buffer is protected. Release the > protection in between setting the buffer and the actual writing in > order for a possible panic (immediate write) to be written during > the scheduling of a previous oops (delayed write). > > An atomic bit (rather than a spinlock) was chosen so that no > scheduling or preemption side-effects would be introduced. The MTD > kmsg_dumper may dump directly or it may be delayed (via scheduled > work). Depending on the context, different MTD callbacks are used. > For example, mtd_write() expects to be called in a non-atomic > context and may take a mutex. > > Signed-off-by: John Ogness > Reviewed-by: Petr Mladek Reviewed-by: Miquel Raynal Thanks, Miquèl 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=-10.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=ham 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 5864DC433DB for ; Thu, 11 Mar 2021 09:51:51 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 C341664D74 for ; Thu, 11 Mar 2021 09:51:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C341664D74 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bootlin.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding :Content-Type:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=3NsavtO9RW3Pe7+7B5VMd3uQc2UV6jOT4ouSham1AiI=; b=cOxDWZ9DCWmI23hZ+nwva48Cj zG9U6mjHnN8vny0vzjtPXHWkqL5xsRe8HKvHKqQZ74G/mAHOPVKvXO/ET16nIn/f9zPp4aLptzwRc nBjCg9ouCxlqzdvopm+ng4XJ/K+dYS5ZPpWTtAZNjwVfe8GnM8kdHwQzhq+npL/BJHa6oJku+l2s8 HCED/LsiF4tyOwCh0IKYzU7Os9P5L7rJJvoevKoNDBjHbe6bjPNhh8w9fUv58q9Y6m49K965NcwMS 6DNsPFs+4q3hsb8l7+0DUya+hJEr6i30W8y3+lCVSROO/i1n2ABT8TpttwNRwLlowynNh5AoGOGmO NghjPOBHQ==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1lKHyH-008mkB-Ks; Thu, 11 Mar 2021 09:51:09 +0000 Received: from relay13.mail.gandi.net ([217.70.178.233]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1lKHy9-008miT-FS for linux-mtd@lists.infradead.org; Thu, 11 Mar 2021 09:51:03 +0000 Received: from xps13 (lfbn-tou-1-1325-59.w90-89.abo.wanadoo.fr [90.89.138.59]) (Authenticated sender: miquel.raynal@bootlin.com) by relay13.mail.gandi.net (Postfix) with ESMTPSA id 6CEA98000D; Thu, 11 Mar 2021 09:50:56 +0000 (UTC) Date: Thu, 11 Mar 2021 10:50:55 +0100 From: Miquel Raynal To: John Ogness Cc: Petr Mladek , Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, Richard Weinberger , Vignesh Raghavendra , linux-mtd@lists.infradead.org Subject: Re: [PATCH next v4 02/15] mtd: mtdoops: synchronize kmsg_dumper Message-ID: <20210311105055.4a0e864d@xps13> In-Reply-To: <20210303101528.29901-3-john.ogness@linutronix.de> References: <20210303101528.29901-1-john.ogness@linutronix.de> <20210303101528.29901-3-john.ogness@linutronix.de> Organization: Bootlin X-Mailer: Claws Mail 3.17.7 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210311_095101_911944_489ACDB8 X-CRM114-Status: GOOD ( 12.55 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org SGVsbG8sCgpKb2huIE9nbmVzcyA8am9obi5vZ25lc3NAbGludXRyb25peC5kZT4gd3JvdGUgb24g V2VkLCAgMyBNYXIgMjAyMQoxMToxNToxNSArMDEwMDoKCj4gVGhlIGttc2dfZHVtcGVyIGNhbiBi ZSBjYWxsZWQgZnJvbSBhbnkgY29udGV4dCBhbmQgQ1BVLCBwb3NzaWJseQo+IGZyb20gbXVsdGlw bGUgQ1BVcyBzaW11bHRhbmVvdXNseS4gU2luY2UgdGhlIHdyaXRpbmcgb2YgdGhlIGJ1ZmZlcgo+ IGNhbiBvY2N1ciBmcm9tIGEgbGF0ZXIgc2NoZWR1bGVkIHdvcmsgcXVldWUsIHRoZSBvb3BzIGJ1 ZmZlciBtdXN0Cj4gYmUgcHJvdGVjdGVkIGFnYWluc3Qgc2ltdWx0YW5lb3VzIGR1bXBpbmcuCj4g Cj4gVXNlIGFuIGF0b21pYyBiaXQgdG8gbWFyayB3aGVuIHRoZSBidWZmZXIgaXMgcHJvdGVjdGVk LiBSZWxlYXNlIHRoZQo+IHByb3RlY3Rpb24gaW4gYmV0d2VlbiBzZXR0aW5nIHRoZSBidWZmZXIg YW5kIHRoZSBhY3R1YWwgd3JpdGluZyBpbgo+IG9yZGVyIGZvciBhIHBvc3NpYmxlIHBhbmljIChp bW1lZGlhdGUgd3JpdGUpIHRvIGJlIHdyaXR0ZW4gZHVyaW5nCj4gdGhlIHNjaGVkdWxpbmcgb2Yg YSBwcmV2aW91cyBvb3BzIChkZWxheWVkIHdyaXRlKS4KPiAKPiBBbiBhdG9taWMgYml0IChyYXRo ZXIgdGhhbiBhIHNwaW5sb2NrKSB3YXMgY2hvc2VuIHNvIHRoYXQgbm8KPiBzY2hlZHVsaW5nIG9y IHByZWVtcHRpb24gc2lkZS1lZmZlY3RzIHdvdWxkIGJlIGludHJvZHVjZWQuIFRoZSBNVEQKPiBr bXNnX2R1bXBlciBtYXkgZHVtcCBkaXJlY3RseSBvciBpdCBtYXkgYmUgZGVsYXllZCAodmlhIHNj aGVkdWxlZAo+IHdvcmspLiBEZXBlbmRpbmcgb24gdGhlIGNvbnRleHQsIGRpZmZlcmVudCBNVEQg Y2FsbGJhY2tzIGFyZSB1c2VkLgo+IEZvciBleGFtcGxlLCBtdGRfd3JpdGUoKSBleHBlY3RzIHRv IGJlIGNhbGxlZCBpbiBhIG5vbi1hdG9taWMKPiBjb250ZXh0IGFuZCBtYXkgdGFrZSBhIG11dGV4 Lgo+IAo+IFNpZ25lZC1vZmYtYnk6IEpvaG4gT2duZXNzIDxqb2huLm9nbmVzc0BsaW51dHJvbml4 LmRlPgo+IFJldmlld2VkLWJ5OiBQZXRyIE1sYWRlayA8cG1sYWRla0BzdXNlLmNvbT4KClJldmll d2VkLWJ5OiBNaXF1ZWwgUmF5bmFsIDxtaXF1ZWwucmF5bmFsQGJvb3RsaW4uY29tPgoKVGhhbmtz LApNaXF1w6hsCgpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX18KTGludXggTVREIGRpc2N1c3Npb24gbWFpbGluZyBsaXN0Cmh0dHA6Ly9saXN0cy5p bmZyYWRlYWQub3JnL21haWxtYW4vbGlzdGluZm8vbGludXgtbXRkLwo=