From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935627AbcLUOhZ (ORCPT ); Wed, 21 Dec 2016 09:37:25 -0500 Received: from mail-pf0-f194.google.com ([209.85.192.194]:35768 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935328AbcLUOhO (ORCPT ); Wed, 21 Dec 2016 09:37:14 -0500 From: Sergey Senozhatsky To: Andrew Morton Cc: Petr Mladek , Jan Kara , Tejun Heo , Calvin Owens , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Andy Lutomirski , Linus Torvalds , Peter Hurley , linux-kernel@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: [PATCHv6 5/7] printk: report lost messages in printk safe/nmi contexts Date: Wed, 21 Dec 2016 23:36:03 +0900 Message-Id: <20161221143605.2272-6-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20161221143605.2272-1-sergey.senozhatsky@gmail.com> References: <20161221143605.2272-1-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(). The patch also moves lost message counter to struct `printk_safe_seq_buf' instead of having dedicated static counters - this simplifies the code. Signed-off-by: Sergey Senozhatsky Reviewed-by: Petr Mladek --- kernel/printk/internal.h | 17 ----------------- kernel/printk/printk.c | 10 ---------- kernel/printk/printk_safe.c | 18 +++++++++++++++--- 3 files changed, 15 insertions(+), 30 deletions(-) diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index 97cee4f482f4..d2456020120c 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 335b0fcb538e..6ec61ae0d122 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1677,7 +1677,6 @@ 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; @@ -1728,15 +1727,6 @@ 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 9e8ef6a2070c..cd5160112374 100644 --- a/kernel/printk/printk_safe.c +++ b/kernel/printk/printk_safe.c @@ -42,10 +42,13 @@ static int printk_safe_irq_ready; #define SAFE_LOG_BUF_LEN ((1 << CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT) - \ - sizeof(atomic_t) - sizeof(struct irq_work)) + sizeof(atomic_t) - \ + sizeof(atomic_t) - \ + sizeof(struct irq_work)) struct printk_safe_seq_buf { atomic_t len; /* length of written data */ + atomic_t message_lost; struct irq_work work; /* IRQ work that flushes the buffer */ unsigned char buffer[SAFE_LOG_BUF_LEN]; }; @@ -55,7 +58,6 @@ static DEFINE_PER_CPU(int, printk_context); #ifdef CONFIG_PRINTK_NMI static DEFINE_PER_CPU(struct printk_safe_seq_buf, nmi_print_seq); -atomic_t nmi_message_lost; #endif /* @@ -79,7 +81,7 @@ static int printk_safe_log_store(struct printk_safe_seq_buf *s, /* The trailing '\0' is not counted into len. */ if (len >= sizeof(s->buffer) - 1) { - atomic_inc(&nmi_message_lost); + atomic_inc(&s->message_lost); return 0; } @@ -168,6 +170,14 @@ static int printk_safe_flush_buffer(const char *start, size_t len) return len; } +static void report_message_lost(struct printk_safe_seq_buf *s) +{ + int lost = atomic_xchg(&s->message_lost, 0); + + if (lost) + printk_deferred("Lost %d message(s)!\n", lost); +} + /* * Flush data from the associated per-CPU buffer. The function * can be called either via IRQ work or independently. @@ -224,6 +234,8 @@ static void __printk_safe_flush(struct irq_work *work) if (atomic_cmpxchg(&s->len, len, 0) != len) goto more; + report_message_lost(s); + out: raw_spin_unlock_irqrestore(&read_lock, flags); } -- 2.11.0