Merge branch 'linus' into x86/apic-cleanups

[cascardo/linux.git] / arch / tile / lib / spinlock_32.c

diff --git a/arch/tile/lib/spinlock_32.c b/arch/tile/lib/spinlock_32.c
index 485e24d..5cd1c40 100644 (file)
--- a/arch/tile/lib/spinlock_32.c
+++ b/arch/tile/lib/spinlock_32.c
@@ -167,23 +167,30 @@ void arch_write_lock_slow(arch_rwlock_t *rwlock, u32 val)
         * when we compare them.
         */
        u32 my_ticket_;
+       u32 iterations = 0;
 
-       /* Take out the next ticket; this will also stop would-be readers. */
-       if (val & 1)
-               val = get_rwlock(rwlock);
-       rwlock->lock = __insn_addb(val, 1 << WR_NEXT_SHIFT);
+       /*
+        * Wait until there are no readers, then bump up the next
+        * field and capture the ticket value.
+        */
+       for (;;) {
+               if (!(val & 1)) {
+                       if ((val >> RD_COUNT_SHIFT) == 0)
+                               break;
+                       rwlock->lock = val;
+               }
+               delay_backoff(iterations++);
+               val = __insn_tns((int *)&rwlock->lock);
+       }
 
-       /* Extract my ticket value from the original word. */
+       /* Take out the next ticket and extract my ticket value. */
+       rwlock->lock = __insn_addb(val, 1 << WR_NEXT_SHIFT);
        my_ticket_ = val >> WR_NEXT_SHIFT;
 
-       /*
-        * Wait until the "current" field matches our ticket, and
-        * there are no remaining readers.
-        */
+       /* Wait until the "current" field matches our ticket. */
        for (;;) {
                u32 curr_ = val >> WR_CURR_SHIFT;
-               u32 readers = val >> RD_COUNT_SHIFT;
-               u32 delta = ((my_ticket_ - curr_) & WR_MASK) + !!readers;
+               u32 delta = ((my_ticket_ - curr_) & WR_MASK);
                if (likely(delta == 0))
                        break;