[PATCH] lockdep: do not recurse in printk
Ingo Molnar [Mon, 3 Jul 2006 07:24:58 +0000 (00:24 -0700)]
Make printk()-ing from within the lock validation code safer by using the
lockdep-recursion counter.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/printk.c

index 39ae24d..bdba5d8 100644 (file)
@@ -518,7 +518,9 @@ asmlinkage int vprintk(const char *fmt, va_list args)
                zap_locks();
 
        /* This stops the holder of console_sem just where we want him */
-       spin_lock_irqsave(&logbuf_lock, flags);
+       local_irq_save(flags);
+       lockdep_off();
+       spin_lock(&logbuf_lock);
        printk_cpu = smp_processor_id();
 
        /* Emit the output into the temporary buffer */
@@ -588,7 +590,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
                 */
                console_locked = 1;
                printk_cpu = UINT_MAX;
-               spin_unlock_irqrestore(&logbuf_lock, flags);
+               spin_unlock(&logbuf_lock);
 
                /*
                 * Console drivers may assume that per-cpu resources have
@@ -604,6 +606,8 @@ asmlinkage int vprintk(const char *fmt, va_list args)
                        console_locked = 0;
                        up(&console_sem);
                }
+               lockdep_on();
+               local_irq_restore(flags);
        } else {
                /*
                 * Someone else owns the drivers.  We drop the spinlock, which
@@ -611,7 +615,9 @@ asmlinkage int vprintk(const char *fmt, va_list args)
                 * console drivers with the output which we just produced.
                 */
                printk_cpu = UINT_MAX;
-               spin_unlock_irqrestore(&logbuf_lock, flags);
+               spin_unlock(&logbuf_lock);
+               lockdep_on();
+               local_irq_restore(flags);
        }
 
        preempt_enable();
@@ -809,8 +815,15 @@ void release_console_sem(void)
        console_may_schedule = 0;
        up(&console_sem);
        spin_unlock_irqrestore(&logbuf_lock, flags);
-       if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait))
-               wake_up_interruptible(&log_wait);
+       if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait)) {
+               /*
+                * If we printk from within the lock dependency code,
+                * from within the scheduler code, then do not lock
+                * up due to self-recursion:
+                */
+               if (!lockdep_internal())
+                       wake_up_interruptible(&log_wait);
+       }
 }
 EXPORT_SYMBOL(release_console_sem);