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 <[email protected]> --- kernel/printk/internal.h | 17 ----------------- kernel/printk/printk.c | 10 ---------- kernel/printk/printk_safe.c | 38 ++++++++++++++++++++++++++++---------- 3 files changed, 28 insertions(+), 37 deletions(-) diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index c65e36509f3b..1db044f808b7 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 9cc9a97c2cc8..86f3f03faf6f 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1676,7 +1676,6 @@ 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; @@ -1727,15 +1726,6 @@ 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 054c9128ade0..04fff7074cce 100644 --- a/kernel/printk/printk_safe.c +++ b/kernel/printk/printk_safe.c @@ -40,13 +40,15 @@ * were handled or when IRQs are blocked. */ static int printk_safe_irq_ready; -atomic_t nmi_message_lost; #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]; }; @@ -58,6 +60,16 @@ static DEFINE_PER_CPU(int, printk_context); static DEFINE_PER_CPU(struct printk_safe_seq_buf, nmi_print_seq); #endif +/* Get flushed in a more safe context. */ +static void queue_flush_work(struct printk_safe_seq_buf *s) +{ + if (printk_safe_irq_ready) { + /* Make sure that IRQ work is really initialized. */ + smp_rmb(); + irq_work_queue(&s->work); + } +} + /* * Add a message to per-CPU context-dependent buffer. NMI and printk-safe * have dedicated buffers, because otherwise printk-safe preempted by @@ -79,7 +91,8 @@ 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); + queue_flush_work(s); return 0; } @@ -91,6 +104,8 @@ static int printk_safe_log_store(struct printk_safe_seq_buf *s, smp_rmb(); add = vscnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, args); + if (!add) + return 0; /* * Do it once again if the buffer has been flushed in the meantime. @@ -100,13 +115,7 @@ static int printk_safe_log_store(struct printk_safe_seq_buf *s, if (atomic_cmpxchg(&s->len, len, len + add) != len) goto again; - /* Get flushed in a more safe context. */ - if (add && printk_safe_irq_ready) { - /* Make sure that IRQ work is really initialized. */ - smp_rmb(); - irq_work_queue(&s->work); - } - + queue_flush_work(s); return add; } @@ -168,6 +177,14 @@ 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. @@ -225,6 +242,7 @@ static void __printk_safe_flush(struct irq_work *work) goto more; out: + report_message_lost(s); raw_spin_unlock_irqrestore(&read_lock, flags); } -- 2.11.0
