diff options
| -rw-r--r-- | kernel/printk.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/kernel/printk.c b/kernel/printk.c index 5092397fac2..a967605bc2e 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -514,6 +514,9 @@ asmlinkage int printk(const char *fmt, ...) return r; } +/* cpu currently holding logbuf_lock */ +static volatile unsigned int printk_cpu = UINT_MAX; + asmlinkage int vprintk(const char *fmt, va_list args) { unsigned long flags; @@ -522,11 +525,15 @@ asmlinkage int vprintk(const char *fmt, va_list args) static char printk_buf[1024]; static int log_level_unknown = 1; - if (unlikely(oops_in_progress)) + preempt_disable(); + if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id()) + /* If a crash is occurring during printk() on this CPU, + * make sure we can't deadlock */ zap_locks(); /* This stops the holder of console_sem just where we want him */ spin_lock_irqsave(&logbuf_lock, flags); + printk_cpu = smp_processor_id(); /* Emit the output into the temporary buffer */ printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args); @@ -595,6 +602,7 @@ asmlinkage int vprintk(const char *fmt, va_list args) * CPU until it is officially up. We shouldn't be calling into * random console drivers on a CPU which doesn't exist yet.. */ + printk_cpu = UINT_MAX; spin_unlock_irqrestore(&logbuf_lock, flags); goto out; } @@ -604,6 +612,7 @@ asmlinkage int vprintk(const char *fmt, va_list args) * We own the drivers. We can drop the spinlock and let * release_console_sem() print the text */ + printk_cpu = UINT_MAX; spin_unlock_irqrestore(&logbuf_lock, flags); console_may_schedule = 0; release_console_sem(); @@ -613,9 +622,11 @@ asmlinkage int vprintk(const char *fmt, va_list args) * allows the semaphore holder to proceed and to call the * console drivers with the output which we just produced. */ + printk_cpu = UINT_MAX; spin_unlock_irqrestore(&logbuf_lock, flags); } out: + preempt_enable(); return printed_len; } EXPORT_SYMBOL(printk); |