From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758238AbcJ0PwB (ORCPT ); Thu, 27 Oct 2016 11:52:01 -0400 Received: from mail-pf0-f194.google.com ([209.85.192.194]:33691 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751011AbcJ0Pvz (ORCPT ); Thu, 27 Oct 2016 11:51:55 -0400 From: Sergey Senozhatsky To: Petr Mladek , Andrew Morton Cc: Jan Kara , Tejun Heo , Calvin Owens , Thomas Gleixner , Mel Gorman , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Laura Abbott , Andy Lutomirski , Linus Torvalds , Kees Cook , linux-kernel@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: [RFC][PATCHv4 4/6] printk: report lost messages in printk safe/nmi contexts Date: Fri, 28 Oct 2016 00:49:31 +0900 Message-Id: <20161027154933.1211-5-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.10.1.502.g6598894 In-Reply-To: <20161027154933.1211-1-sergey.senozhatsky@gmail.com> References: <20161027154933.1211-1-sergey.senozhatsky@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Account lost messages in pritk-safe and printk-safe-nmi contexts and report those numbers during printk_safe_flush(). Signed-off-by: Sergey Senozhatsky --- kernel/printk/internal.h | 17 --------------- kernel/printk/printk.c | 10 --------- kernel/printk/printk_safe.c | 50 +++++++++++++++++++++++++++++++++++++++++++-- 3 files changed, 48 insertions(+), 29 deletions(-) diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index 87c784b..384542d 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -16,23 +16,6 @@ */ #include -#ifdef CONFIG_PRINTK_NMI - -extern atomic_t nmi_message_lost; -static inline int get_nmi_message_lost(void) -{ - return atomic_xchg(&nmi_message_lost, 0); -} - -#else /* CONFIG_PRINTK_NMI */ - -static inline int get_nmi_message_lost(void) -{ - return 0; -} - -#endif /* CONFIG_PRINTK_NMI */ - #ifdef CONFIG_PRINTK #define PRINTK_SAFE_CONTEXT_MASK 0x7fffffff diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 1878b2d..4675b8d 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1795,7 +1795,6 @@ asmlinkage int vprintk_emit(int facility, int level, unsigned long flags; int this_cpu; int printed_len = 0; - int nmi_message_lost; bool in_sched = false; /* cpu currently holding logbuf_lock in this function */ static unsigned int logbuf_cpu = UINT_MAX; @@ -1846,15 +1845,6 @@ asmlinkage int vprintk_emit(int facility, int level, strlen(recursion_msg)); } - nmi_message_lost = get_nmi_message_lost(); - if (unlikely(nmi_message_lost)) { - text_len = scnprintf(textbuf, sizeof(textbuf), - "BAD LUCK: lost %d message(s) from NMI context!", - nmi_message_lost); - printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0, - NULL, 0, textbuf, text_len); - } - /* * The printf needs to come first; we need the syslog * prefix which might be passed-in as a parameter. diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c index af74d9c..721b091 100644 --- a/kernel/printk/printk_safe.c +++ b/kernel/printk/printk_safe.c @@ -52,10 +52,11 @@ struct printk_safe_seq_buf { static DEFINE_PER_CPU(struct printk_safe_seq_buf, safe_print_seq); static DEFINE_PER_CPU(int, printk_safe_context); +static atomic_t safe_message_lost; #ifdef CONFIG_PRINTK_NMI static DEFINE_PER_CPU(struct printk_safe_seq_buf, nmi_print_seq); -atomic_t nmi_message_lost; +static atomic_t nmi_message_lost; #endif static int printk_safe_log_store(struct printk_safe_seq_buf *s, @@ -122,6 +123,41 @@ static void printk_safe_flush_seq_line(struct printk_safe_seq_buf *s, printk_safe_flush_line(buf, (end - start) + 1); } +static void report_message_lost(atomic_t *num_lost, char *fmt) +{ + int lost = atomic_xchg(num_lost, 0); + + if (lost) { + char msg[56]; + + scnprintf(msg, sizeof(msg), fmt, lost); + + printk_safe_flush_line(msg, strlen(msg)); + } +} + +#ifdef CONFIG_PRINTK_NMI + +static void report_nmi_message_lost(void) +{ + report_message_lost(&nmi_message_lost, + "Lost %d message(s) from NMI context!"); +} + +#else + +static void report_nmi_message_lost(void) +{ +} + +#endif /* CONFIG_PRINTK_NMI */ + +static void report_safe_message_lost(void) +{ + report_message_lost(&safe_message_lost, + "Lost %d message(s) from printk-safe context!"); +} + /* * Flush data from the associated per-CPU buffer. The function * can be called either via IRQ work or independently. @@ -147,6 +183,9 @@ static void __printk_safe_flush(struct irq_work *work) i = 0; more: + report_nmi_message_lost(); + report_safe_message_lost(); + len = atomic_read(&s->len); /* @@ -289,8 +328,15 @@ static int vprintk_safe_nmi(const char *fmt, va_list args) static int vprintk_safe(const char *fmt, va_list args) { struct printk_safe_seq_buf *s = this_cpu_ptr(&safe_print_seq); + int add; - return printk_safe_log_store(s, fmt, args); + add = printk_safe_log_store(s, fmt, args); + if (add == -E2BIG) { + atomic_inc(&safe_message_lost); + add = 0; + } + + return add; } /* Can be preempted by NMI. */ -- 2.10.1.502.g6598894