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=-9.3 required=3.0 tests=BAYES_00, BUG6152_INVALID_DATE_TZ_ABSURD,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,INVALID_DATE_TZ_ABSURD, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 682CEC2D0E2 for ; Tue, 22 Sep 2020 15:38:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 287422220D for ; Tue, 22 Sep 2020 15:38:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="uZwhRFYR"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="V8gofiI/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726776AbgIVPiZ (ORCPT ); Tue, 22 Sep 2020 11:38:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48418 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726746AbgIVPiU (ORCPT ); Tue, 22 Sep 2020 11:38:20 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 18A6EC061755 for ; Tue, 22 Sep 2020 08:38:20 -0700 (PDT) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1600789098; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=UCCVgMcycqiESfhtnp0v+kLf2CKu8F8FiQ7NWkVtMBo=; b=uZwhRFYRj8v0Vd9rM1JFfvO+bTFu8V97oBFsYJ+PbpjDLjRvu41+hclsjGqagvOZ7O/ch6 Udb0rKO1k+olT9ey5EASBYnMdP/yqrU5IZJ4P2pcbTqJb7smFEMKfFp9rxONf9bRx6lfje m2Ha3XR0/2SfRJ79vQ/2ioW3gKHwTICTd4K/9TPuDU+w2noDQz/Mn7YmDfMekkUDPpMPQY ZHWVrmt7T5G2p144LdXiZTtQ4RIuP88t0/Auejz/Gzcar3H41LC7zlDi2rr+p6XKKdI83k pRkfiEvtsfO/buj/Bip3gyGi7xUvDXMjizBtP7zgYVoKqAJZyODzVcGXnkJhNg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1600789098; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=UCCVgMcycqiESfhtnp0v+kLf2CKu8F8FiQ7NWkVtMBo=; b=V8gofiI/fyx/zVF97kud1sB8OfqVKP69dqBfpTRj1p850+SvWvx0y1Ly8E5QcZW0CQXXSC EPDy/DEiTtkezHDg== To: Petr Mladek Cc: Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH printk 2/5] printk: kmsg_dump_rewind_nolock: start from first record Date: Tue, 22 Sep 2020 17:44:13 +0206 Message-Id: <20200922153816.5883-3-john.ogness@linutronix.de> In-Reply-To: <20200922153816.5883-1-john.ogness@linutronix.de> References: <20200922153816.5883-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kmsg_dump_rewind_nolock() accesses @clear_seq without any locking. However, accessing this global variable requires holding @logbuf_lock. For the _nolock() variant, start from the first record in the ringbuffer rather than the @clear_seq record. Signed-off-by: John Ogness --- kernel/printk/printk.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 00bc1fce3299..cff13b33e926 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3410,11 +3410,12 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer); * kmsg_dump_get_buffer() can be called again and used multiple * times within the same dumper.dump() callback. * - * The function is similar to kmsg_dump_rewind(), but grabs no locks. + * The function is similar to kmsg_dump_rewind(), but grabs no locks + * and starts from the oldest record rather than from @clear_seq. */ void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper) { - dumper->cur_seq = clear_seq; + dumper->cur_seq = 0; dumper->next_seq = prb_next_seq(prb); } @@ -3431,7 +3432,8 @@ void kmsg_dump_rewind(struct kmsg_dumper *dumper) unsigned long flags; logbuf_lock_irqsave(flags); - kmsg_dump_rewind_nolock(dumper); + dumper->cur_seq = clear_seq; + dumper->next_seq = prb_next_seq(prb); logbuf_unlock_irqrestore(flags); } EXPORT_SYMBOL_GPL(kmsg_dump_rewind); -- 2.20.1