Account lost messages in pritk-safe and printk-safe-nmi contexts and report those numbers during printk_safe_flush().
Signed-off-by: Sergey Senozhatsky <[email protected]> --- kernel/printk/internal.h | 17 ----------------- kernel/printk/printk.c | 10 ---------- kernel/printk/printk_safe.c | 45 +++++++++++++++++++++++++++++++++++++++++++-- 3 files changed, 43 insertions(+), 29 deletions(-) diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index 97cee4f..d245602 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -16,23 +16,6 @@ */ #include <linux/percpu.h> -#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 77446ba..6f7b217 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1776,7 +1776,6 @@ 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; @@ -1827,15 +1826,6 @@ 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 3ded9e1..0689b94 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_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, @@ -155,6 +156,36 @@ static int printk_safe_flush_buffer(const char *start, size_t len) return len; } +static void report_message_lost(atomic_t *num_lost, const char *context) +{ + int lost = atomic_xchg(num_lost, 0); + + if (lost) + printk_deferred("Lost %d message(s) from %s context!\n", + lost, + context); +} + +#ifdef CONFIG_PRINTK_NMI + +static void report_nmi_message_lost(void) +{ + report_message_lost(&nmi_message_lost, "NMI"); +} + +#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, "printk-safe"); +} + /* * Flush data from the associated per-CPU buffer. The function * can be called either via IRQ work or independently. @@ -211,6 +242,9 @@ static void __printk_safe_flush(struct irq_work *work) if (atomic_cmpxchg(&s->len, len, 0) != len) goto more; + report_nmi_message_lost(); + report_safe_message_lost(); + out: raw_spin_unlock_irqrestore(&read_lock, flags); } @@ -309,8 +343,15 @@ 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 == -ENOSPC) { + atomic_inc(&safe_message_lost); + add = 0; + } + + return add; } /* Can be preempted by NMI. */ -- 2.10.2
