-/* write_lock is less trivial. We optimistically grab the lock and check
- * if we surprised any readers. If so we release the lock and wait till
- * they're all gone before trying again
- *
- * Also note that we don't use the _irqsave / _irqrestore suffixes here.
- * If we're called with interrupts enabled and we've got readers (or other
- * writers) in interrupt handlers someone fucked up and we'd dead-lock
- * sooner or later anyway. prumpf */
+/* Note that we have to ensure interrupts are disabled in case we're
+ * interrupted by some other code that wants to grab the same read lock */
+static __inline__ int __raw_read_trylock(raw_rwlock_t *rw)
+{
+ unsigned long flags;
+ retry:
+ local_irq_save(flags);
+ if (__raw_spin_trylock(&rw->lock)) {
+ rw->counter++;
+ __raw_spin_unlock(&rw->lock);
+ local_irq_restore(flags);
+ return 1;
+ }
+
+ local_irq_restore(flags);
+ /* If write-locked, we fail to acquire the lock */
+ if (rw->counter < 0)
+ return 0;
+
+ /* Wait until we have a realistic chance at the lock */
+ while (__raw_spin_is_locked(&rw->lock) && rw->counter >= 0)
+ cpu_relax();