Merge branch 'upstream' of master.kernel.org:/pub/scm/linux/kernel/git/jgarzik/misc-2.6

[sfrench/cifs-2.6.git] / kernel / printk.c

diff --git a/kernel/printk.c b/kernel/printk.c
index 5092397fac29926bfab6da75fc273882b14e905d..a967605bc2e358cbcf95dd7fe60f7870fe9dd14b 100644 (file)
--- 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);