Merge branch 'sh/urgent' into sh-latest

1 files changed, 18 insertions, 11 deletions

diff --git a/arch/tile/lib/spinlock_32.c b/arch/tile/lib/spinlock_32.c
index 485e24d62c6b..5cd1c4004eca 100644
--- 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;