On Fri, 21 Jan 2011 09:10:06 +0100 Geert Uytterhoeven [off-list ref] wrote:

include/linux/mutex.h:

/*
 * NOTE: mutex_trylock() follows the spin_trylock() convention,
 *       not the down_trylock() convention!
 *
 * Returns 1 if the mutex has been acquired successfully, and 0 on contention.
 */
extern int mutex_trylock(struct mutex *lock);

So that's why the return value was inverted (when treating it as a boolean).
I can understand that.

However:

+/**
+ * console_trylock - try to lock the console system for exclusive use.
+ *
+ * Tried to acquire a lock which guarantees that the caller has
+ * exclusive access to the console system and the console_drivers list.
+ *
+ * returns -1 on success, and 0 on failure to acquire the lock.
+ */
+int console_trylock(void)

So this one returns -1 on success, not 1? Why?

Yup.  All callers just test for non-zero, so...

--- a/kernel/printk.c~change-acquire-release_console_sem-to-console_lock-unlock-fix-2
+++ a/kernel/printk.c

@@ -1058,7 +1058,7 @@ EXPORT_SYMBOL(console_lock);
  * Tried to acquire a lock which guarantees that the caller has
  * exclusive access to the console system and the console_drivers list.
  *
- * returns -1 on success, and 0 on failure to acquire the lock.
+ * returns 1 on success, and 0 on failure to acquire the lock.
  */
 int console_trylock(void)
 {

@@ -1070,7 +1070,7 @@ int console_trylock(void)
 	}
 	console_locked = 1;
 	console_may_schedule = 0;
-	return -1;
+	return 1;
 }
 EXPORT_SYMBOL(console_trylock);
 

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