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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 ED19DC43381 for ; Thu, 25 Feb 2021 20:25:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BB92B64F56 for ; Thu, 25 Feb 2021 20:25:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233293AbhBYUZh (ORCPT ); Thu, 25 Feb 2021 15:25:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230386AbhBYUZY (ORCPT ); Thu, 25 Feb 2021 15:25:24 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D3C00C061756 for ; Thu, 25 Feb 2021 12:24:43 -0800 (PST) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1614284680; 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=2PsPa8qMZnWwUb4jHsmd/hQaRjESGDEH7IccbrBhwY0=; b=bhbU7YwMBvimdKvYGnhePinmZs38v5Eo4N8r/KTFAuEXAzI7j8AJbtEKMmFxiiBVeLkKvi ao6hrO4nIVYZPGehFgSe9LhMduVdiEs6r80eavZcayaQuNZs4Heq1aJzjI4fcXaY7+9fJt quqeyDvDgwl3UBqnGqpdE6MpygbKYh1RJz48OlX8bPQeW3KewRZNKGr2gl5VrwHrFtVfOr gvg0vngGmaR4Lbr/3isDqzZygjZXgE6X/a/xu25X3He0UV3WH0425UYkmafdOx804m3g02 kF+lrIJ9T2ndSSxc1j0TR4VsD26P/wIhpUVkgGEWA7j1lkg+6Zf8oTOT2EH+SQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1614284680; 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=2PsPa8qMZnWwUb4jHsmd/hQaRjESGDEH7IccbrBhwY0=; b=4U2fWzVfVlarqsfvvMAFJYgi9lBy8gSF94jFIX7ke6zS6m7vc1YI39uScih1UfkS4DlJ/j 1b4F5xB/wXjRGKCw== To: Petr Mladek Cc: Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org, Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , linux-mtd@lists.infradead.org Subject: [PATCH next v3 02/15] mtd: mtdoops: synchronize kmsg_dumper Date: Thu, 25 Feb 2021 21:24:25 +0100 Message-Id: <20210225202438.28985-3-john.ogness@linutronix.de> In-Reply-To: <20210225202438.28985-1-john.ogness@linutronix.de> References: <20210225202438.28985-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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). Signed-off-by: John Ogness --- drivers/mtd/mtdoops.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c index 774970bfcf85..8bbfba40a554 100644 --- a/drivers/mtd/mtdoops.c +++ b/drivers/mtd/mtdoops.c @@ -52,6 +52,7 @@ static struct mtdoops_context { int nextcount; unsigned long *oops_page_used; + unsigned long oops_buf_busy; void *oops_buf; } oops_cxt; @@ -180,6 +181,9 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic) u32 *hdr; int ret; + if (test_and_set_bit(0, &cxt->oops_buf_busy)) + return; + /* Add mtdoops header to the buffer */ hdr = cxt->oops_buf; hdr[0] = cxt->nextcount; @@ -190,7 +194,7 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic) record_size, &retlen, cxt->oops_buf); if (ret == -EOPNOTSUPP) { printk(KERN_ERR "mtdoops: Cannot write from panic without panic_write\n"); - return; + goto out; } } else ret = mtd_write(mtd, cxt->nextpage * record_size, @@ -203,6 +207,8 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic) memset(cxt->oops_buf, 0xff, record_size); mtdoops_inc_counter(cxt); +out: + clear_bit(0, &cxt->oops_buf_busy); } static void mtdoops_workfunc_write(struct work_struct *work) @@ -276,8 +282,11 @@ static void mtdoops_do_dump(struct kmsg_dumper *dumper, if (reason == KMSG_DUMP_OOPS && !dump_oops) return; + if (test_and_set_bit(0, &cxt->oops_buf_busy)) + return; kmsg_dump_get_buffer(dumper, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE, record_size - MTDOOPS_HEADER_SIZE, NULL); + clear_bit(0, &cxt->oops_buf_busy); if (reason != KMSG_DUMP_OOPS) { /* Panics must be written immediately */ @@ -394,6 +403,7 @@ static int __init mtdoops_init(void) return -ENOMEM; } memset(cxt->oops_buf, 0xff, record_size); + cxt->oops_buf_busy = 0; INIT_WORK(&cxt->work_erase, mtdoops_workfunc_erase); INIT_WORK(&cxt->work_write, mtdoops_workfunc_write); -- 2.20.1