Fix some bugs related to adaptive spinning:

In the lockmgr support:
- GIANT_RESTORE() is just called when the sleep finishes, so the current
  code can ends up into a giant unlock problem.  Fix it by appropriately
  call GIANT_RESTORE() when needed.  Note that this is not exactly ideal
  because for any interation of the adaptive spinning we drop and restore
  Giant, but the overhead should be not a factor.
- In the lock held in exclusive mode case, after the adaptive spinning is
  brought to completition, we should just retry to acquire the lock
  instead to fallthrough. Fix that.
- Fix a style nit

In the sx support:
- Call GIANT_SAVE() before than looping. This saves some overhead because
  in the current code GIANT_SAVE() is called several times.

Tested by:	Giovanni Trematerra <giovanni dot trematerra at gmail dot com>

1 files changed, 1 insertions, 1 deletions

diff --git a/sys/kern/kern_sx.c b/sys/kern/kern_sx.c
index 4a78444..c00b267 100644
--- a/sys/kern/kern_sx.c
+++ b/sys/kern/kern_sx.c
@@ -531,13 +531,13 @@ _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, const char *file,
 					continue;
 				}
 			} else if (SX_SHARERS(x) && spintries < asx_retries) {
+				GIANT_SAVE();
 				spintries++;
 				for (i = 0; i < asx_loops; i++) {
 					if (LOCK_LOG_TEST(&sx->lock_object, 0))
 						CTR4(KTR_LOCK,
 				    "%s: shared spinning on %p with %u and %u",
 						    __func__, sx, spintries, i);
-					GIANT_SAVE();
 					x = sx->sx_lock;
 					if ((x & SX_LOCK_SHARED) == 0 ||
 					    SX_SHARERS(x) == 0)