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[2620:137:e000::1:20]) by mx.google.com with ESMTP id h26-20020aa796da000000b00587cafeea1bsi155504pfq.379.2023.03.02.12.00.13; Thu, 02 Mar 2023 12:00:26 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b=YMCQ3Q5j; dkim=neutral (no key) header.i=@linutronix.de header.b=6LDiB0rm; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230139AbjCBT6G (ORCPT + 99 others); Thu, 2 Mar 2023 14:58:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54794 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229794AbjCBT5q (ORCPT ); Thu, 2 Mar 2023 14:57:46 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62044474DE for ; Thu, 2 Mar 2023 11:57:44 -0800 (PST) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1677787063; 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=P2i344YuQotLWLLh6A7EkhSEbuMCwNrp9Bq5Z1X7/c0=; b=YMCQ3Q5j0mLRMU57xKPv0P3mSbWo0Ywjx2iCdMhsDuTXc1VGeoD7OhwB3PZioa1Q6rBV5x op9kGRs7DNY2tbQ+m6gUZxo8isQ4uWQzwqGlv4d2PFhAfuJbrKmW0oigkvHuDDS0mEYedn K09hhIZChvrQnP6jg13NnsoxEYMUXKke8zh/k3+wNURrPYkk1hC1Wp9WTHo2lLesvw8qiq 2yzsCgLNrX30Ebq2zr+YcKqFBwTlbsBWY1TltUhSJqP5LyVMzHRBX1djhklF0Q5sCoHXcH CTFE6ChYtFsBfkrRFpCI9O/wU7BaD4JQkDUqKq9HeQuz8WjxVSm6Pz53lSXeHA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1677787063; 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=P2i344YuQotLWLLh6A7EkhSEbuMCwNrp9Bq5Z1X7/c0=; b=6LDiB0rmVnvPOZP6uR2CnybeIo6zVvSY0985uqwkaHrhDpNtH84j+OHtP7kKDCT1pBWMmC Vrc8je4gESeoJrDg== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH printk v1 03/18] printk: Consolidate console deferred printing Date: Thu, 2 Mar 2023 21:02:03 +0106 Message-Id: <20230302195618.156940-4-john.ogness@linutronix.de> In-Reply-To: <20230302195618.156940-1-john.ogness@linutronix.de> References: <20230302195618.156940-1-john.ogness@linutronix.de> MIME-Version: 1.0 X-Spam-Status: No, score=-3.9 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,INVALID_DATE_TZ_ABSURD, RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1759287419354305911?= X-GMAIL-MSGID: =?utf-8?q?1759287419354305911?= Printig to consoles can be deferred for several reasons: - explicitly with printk_deferred() - printk() in NMI context - recursive printk() calls The current implementation is not consistent. For printk_deferred(), irq work is scheduled twice. For NMI und recursive, panic CPU suppression and caller delays are not properly enforced. Correct these inconsistencies by consolidating the deferred printing code so that vprintk_deferred() is the toplevel function for deferred printing and vprintk_emit() will perform whichever irq_work queueing is appropriate. Also add kerneldoc for wake_up_klogd() and defer_console_output() to clarify their differences and appropriate usage. Signed-off-by: John Ogness --- kernel/printk/printk.c | 31 ++++++++++++++++++++++++------- kernel/printk/printk_safe.c | 9 ++------- 2 files changed, 26 insertions(+), 14 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 84af038292d9..bdeaf12e0bd2 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2321,7 +2321,10 @@ asmlinkage int vprintk_emit(int facility, int level, preempt_enable(); } - wake_up_klogd(); + if (in_sched) + defer_console_output(); + else + wake_up_klogd(); return printed_len; } EXPORT_SYMBOL(vprintk_emit); @@ -3811,11 +3814,30 @@ static void __wake_up_klogd(int val) preempt_enable(); } +/** + * wake_up_klogd - Wake kernel logging daemon + * + * Use this function when new records have been added to the ringbuffer + * and the console printing for those records is handled elsewhere. In + * this case only the logging daemon needs to be woken. + * + * Context: Any context. + */ void wake_up_klogd(void) { __wake_up_klogd(PRINTK_PENDING_WAKEUP); } +/** + * defer_console_output - Wake kernel logging daemon and trigger + * console printing in a deferred context + * + * Use this function when new records have been added to the ringbuffer + * but the current context is unable to perform the console printing. + * This function also wakes the logging daemon. + * + * Context: Any context. + */ void defer_console_output(void) { /* @@ -3832,12 +3854,7 @@ void printk_trigger_flush(void) int vprintk_deferred(const char *fmt, va_list args) { - int r; - - r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, fmt, args); - defer_console_output(); - - return r; + return vprintk_emit(0, LOGLEVEL_SCHED, NULL, fmt, args); } int _printk_deferred(const char *fmt, ...) diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c index ef0f9a2044da..6d10927a07d8 100644 --- a/kernel/printk/printk_safe.c +++ b/kernel/printk/printk_safe.c @@ -38,13 +38,8 @@ asmlinkage int vprintk(const char *fmt, va_list args) * Use the main logbuf even in NMI. But avoid calling console * drivers that might have their own locks. */ - if (this_cpu_read(printk_context) || in_nmi()) { - int len; - - len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, fmt, args); - defer_console_output(); - return len; - } + if (this_cpu_read(printk_context) || in_nmi()) + return vprintk_deferred(fmt, args); /* No obstacles. */ return vprintk_default(fmt, args);