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=-15.2 required=3.0 tests=BAYES_00, BUG6152_INVALID_DATE_TZ_ABSURD,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, INVALID_DATE_TZ_ABSURD,MAILING_LIST_MULTI,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 3ADBEC64E7B for ; Tue, 1 Dec 2020 20:54:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CDE1121D42 for ; Tue, 1 Dec 2020 20:54:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="1yJV/8P/"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="xj9j9Mv7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388233AbgLAUy0 (ORCPT ); Tue, 1 Dec 2020 15:54:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49506 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387749AbgLAUyZ (ORCPT ); Tue, 1 Dec 2020 15:54:25 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 34CE7C0613D4 for ; Tue, 1 Dec 2020 12:53:45 -0800 (PST) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1606856023; 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=sq95sUO9fKYASLRl2y1kd2fJ7DXU9bSXwie9b2JJ7YM=; b=1yJV/8P/XsPFH/nK015x6fNmimWs5j4CmDPMjRqSd/oIKa18/WYejFHEfnRQbfNq45eksj RTR9TypS7wmMuFBg2c4dgr+pAdSTNYD2/63UrkDdsX42GPpbB5Xeu7wOkCVqByQ5O/MIA5 nRnLBegOItJwyXhHFIXQCzmeruQcun4JqDvkDSUSxwORr05Lp3w6q2URpj62Usbyr/y2h3 puo9kgrlkzscH9ZiSpr3LjCiyXvjBHoNGP4yJFlM09rwBYyZUU4KGE25zd4uSJpRxhs6M0 PfwchPt0QrcJtAIQoqNzzwXtkaPoPjkXDOz1XBSlk6+WsAQ724NwMA6Mss33dA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1606856023; 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=sq95sUO9fKYASLRl2y1kd2fJ7DXU9bSXwie9b2JJ7YM=; b=xj9j9Mv7mJyFO2PdoH8SfiufDcbzQ2Rt+oWs3A02Q8clyFWamN7onhTBDviGCpOSJ9nEiQ hAh4RUKCjLv0hMDQ== To: Petr Mladek Cc: Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH next v2 2/3] printk: change @clear_seq to atomic64_t Date: Tue, 1 Dec 2020 21:59:40 +0106 Message-Id: <20201201205341.3871-3-john.ogness@linutronix.de> In-Reply-To: <20201201205341.3871-1-john.ogness@linutronix.de> References: <20201201205341.3871-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently @clear_seq access is protected by @logbuf_lock. Once @logbuf_lock is removed some other form of synchronization will be required. Change the type of @clear_seq to atomic64_t to provide the synchronization. Signed-off-by: John Ogness --- kernel/printk/printk.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index fc5e3a7d6d89..e9018c4e1b66 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -403,7 +403,7 @@ static u64 exclusive_console_stop_seq; static unsigned long console_dropped; /* the next printk record to read after the last 'clear' command */ -static u64 clear_seq; +static atomic64_t clear_seq = ATOMIC64_INIT(0); #ifdef CONFIG_PRINTK_CALLER #define PREFIX_MAX 48 @@ -797,7 +797,7 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence) * like issued by 'dmesg -c'. Reading /dev/kmsg itself * changes no global state, and does not clear anything. */ - user->seq = clear_seq; + user->seq = atomic64_read(&clear_seq); break; case SEEK_END: /* after the last record */ @@ -914,6 +914,9 @@ void log_buf_vmcoreinfo_setup(void) * parse it and detect any changes to structure down the line. */ + VMCOREINFO_SIZE(atomic64_t); + VMCOREINFO_TYPE_OFFSET(atomic64_t, counter); + VMCOREINFO_STRUCT_SIZE(printk_ringbuffer); VMCOREINFO_OFFSET(printk_ringbuffer, desc_ring); VMCOREINFO_OFFSET(printk_ringbuffer, text_data_ring); @@ -1476,6 +1479,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) struct printk_info info; unsigned int line_count; struct printk_record r; + u64 clr_seq; char *text; int len = 0; u64 seq; @@ -1487,15 +1491,17 @@ static int syslog_print_all(char __user *buf, int size, bool clear) time = printk_time; logbuf_lock_irq(); + clr_seq = atomic64_read(&clear_seq); + /* * Find first record that fits, including all following records, * into the user-provided buffer for this dump. */ - prb_for_each_info(clear_seq, prb, seq, &info, &line_count) + prb_for_each_info(clr_seq, prb, seq, &info, &line_count) len += get_record_print_text_size(&info, line_count, true, time); /* move first record forward until length fits into the buffer */ - prb_for_each_info(clear_seq, prb, seq, &info, &line_count) { + prb_for_each_info(clr_seq, prb, seq, &info, &line_count) { if (len <= size) break; len -= get_record_print_text_size(&info, line_count, true, time); @@ -1526,7 +1532,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) } if (clear) - clear_seq = seq; + atomic64_set(&clear_seq, seq); logbuf_unlock_irq(); kfree(text); @@ -1536,7 +1542,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) static void syslog_clear(void) { logbuf_lock_irq(); - clear_seq = prb_next_seq(prb); + atomic64_set(&clear_seq, prb_next_seq(prb)); logbuf_unlock_irq(); } @@ -3205,7 +3211,7 @@ void kmsg_dump(enum kmsg_dump_reason reason) dumper->active = true; logbuf_lock_irqsave(flags); - dumper->cur_seq = clear_seq; + dumper->cur_seq = atomic64_read(&clear_seq); dumper->next_seq = prb_next_seq(prb); logbuf_unlock_irqrestore(flags); @@ -3412,7 +3418,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer); */ void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper) { - dumper->cur_seq = clear_seq; + dumper->cur_seq = atomic64_read(&clear_seq); dumper->next_seq = prb_next_seq(prb); } -- 2.20.1