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Diffstat (limited to 'kernel/printk.c')
-rw-r--r--kernel/printk.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/kernel/printk.c b/kernel/printk.c
index 5092397fac29..a967605bc2e3 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -514,6 +514,9 @@ asmlinkage int printk(const char *fmt, ...)
514 return r; 514 return r;
515} 515}
516 516
517/* cpu currently holding logbuf_lock */
518static volatile unsigned int printk_cpu = UINT_MAX;
519
517asmlinkage int vprintk(const char *fmt, va_list args) 520asmlinkage int vprintk(const char *fmt, va_list args)
518{ 521{
519 unsigned long flags; 522 unsigned long flags;
@@ -522,11 +525,15 @@ asmlinkage int vprintk(const char *fmt, va_list args)
522 static char printk_buf[1024]; 525 static char printk_buf[1024];
523 static int log_level_unknown = 1; 526 static int log_level_unknown = 1;
524 527
525 if (unlikely(oops_in_progress)) 528 preempt_disable();
529 if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
530 /* If a crash is occurring during printk() on this CPU,
531 * make sure we can't deadlock */
526 zap_locks(); 532 zap_locks();
527 533
528 /* This stops the holder of console_sem just where we want him */ 534 /* This stops the holder of console_sem just where we want him */
529 spin_lock_irqsave(&logbuf_lock, flags); 535 spin_lock_irqsave(&logbuf_lock, flags);
536 printk_cpu = smp_processor_id();
530 537
531 /* Emit the output into the temporary buffer */ 538 /* Emit the output into the temporary buffer */
532 printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args); 539 printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
@@ -595,6 +602,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
595 * CPU until it is officially up. We shouldn't be calling into 602 * CPU until it is officially up. We shouldn't be calling into
596 * random console drivers on a CPU which doesn't exist yet.. 603 * random console drivers on a CPU which doesn't exist yet..
597 */ 604 */
605 printk_cpu = UINT_MAX;
598 spin_unlock_irqrestore(&logbuf_lock, flags); 606 spin_unlock_irqrestore(&logbuf_lock, flags);
599 goto out; 607 goto out;
600 } 608 }
@@ -604,6 +612,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
604 * We own the drivers. We can drop the spinlock and let 612 * We own the drivers. We can drop the spinlock and let
605 * release_console_sem() print the text 613 * release_console_sem() print the text
606 */ 614 */
615 printk_cpu = UINT_MAX;
607 spin_unlock_irqrestore(&logbuf_lock, flags); 616 spin_unlock_irqrestore(&logbuf_lock, flags);
608 console_may_schedule = 0; 617 console_may_schedule = 0;
609 release_console_sem(); 618 release_console_sem();
@@ -613,9 +622,11 @@ asmlinkage int vprintk(const char *fmt, va_list args)
613 * allows the semaphore holder to proceed and to call the 622 * allows the semaphore holder to proceed and to call the
614 * console drivers with the output which we just produced. 623 * console drivers with the output which we just produced.
615 */ 624 */
625 printk_cpu = UINT_MAX;
616 spin_unlock_irqrestore(&logbuf_lock, flags); 626 spin_unlock_irqrestore(&logbuf_lock, flags);
617 } 627 }
618out: 628out:
629 preempt_enable();
619 return printed_len; 630 return printed_len;
620} 631}
621EXPORT_SYMBOL(printk); 632EXPORT_SYMBOL(printk);