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, ...)
         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);