Author: mjg
Date: Fri Jul 13 22:40:14 2018
New Revision: 336267
URL: https://svnweb.freebsd.org/changeset/base/336267
Log:
lockmgr: tidy up slock/sunlock similar to other locks
Modified:
head/sys/kern/kern_lock.c
Modified: head/sys/kern/kern_lock.c
==============================================================================
--- head/sys/kern/kern_lock.c Fri Jul 13 21:30:18 2018 (r336266)
+++ head/sys/kern/kern_lock.c Fri Jul 13 22:40:14 2018 (r336267)
@@ -112,11 +112,21 @@ CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
} \
} while (0)
-#define LK_CAN_SHARE(x, flags)
\
- (((x) & LK_SHARE) && \
- (((x) & (LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) == 0 || \
- (curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) || \
- (curthread->td_pflags & TDP_DEADLKTREAT)))
+static bool __always_inline
+LK_CAN_SHARE(uintptr_t x, int flags, bool fp)
+{
+
+ if ((x & (LK_SHARE | LK_EXCLUSIVE_WAITERS | LK_EXCLUSIVE_SPINNERS)) ==
+ LK_SHARE)
+ return (true);
+ if (fp || (!(x & LK_SHARE)))
+ return (false);
+ if ((curthread->td_lk_slocks != 0 && !(flags & LK_NODDLKTREAT)) ||
+ (curthread->td_pflags & TDP_DEADLKTREAT))
+ return (true);
+ return (false);
+}
+
#define LK_TRYOP(x)
\
((x) & LK_NOWAIT)
@@ -169,7 +179,7 @@ struct lockmgr_wait {
};
static bool __always_inline lockmgr_slock_try(struct lock *lk, uintptr_t *xp,
- int flags);
+ int flags, bool fp);
static bool __always_inline lockmgr_sunlock_try(struct lock *lk, uintptr_t
*xp);
static void
@@ -498,7 +508,7 @@ lockdestroy(struct lock *lk)
}
static bool __always_inline
-lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags)
+lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int flags, bool fp)
{
/*
@@ -509,7 +519,7 @@ lockmgr_slock_try(struct lock *lk, uintptr_t *xp, int
* loop back and retry.
*/
*xp = lk->lk_lock;
- while (LK_CAN_SHARE(*xp, flags)) {
+ while (LK_CAN_SHARE(*xp, flags, fp)) {
if (atomic_fcmpset_acq_ptr(&lk->lk_lock, xp,
*xp + LK_ONE_SHARER)) {
return (true);
@@ -523,29 +533,12 @@ lockmgr_sunlock_try(struct lock *lk, uintptr_t *xp)
{
for (;;) {
- /*
- * If there is more than one shared lock held, just drop one
- * and return.
- */
- if (LK_SHARERS(*xp) > 1) {
+ if (LK_SHARERS(*xp) > 1 || !(*xp & LK_ALL_WAITERS)) {
if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp,
*xp - LK_ONE_SHARER))
return (true);
continue;
}
-
- /*
- * If there are not waiters on the exclusive queue, drop the
- * lock quickly.
- */
- if ((*xp & LK_ALL_WAITERS) == 0) {
- MPASS((*xp & ~LK_EXCLUSIVE_SPINNERS) ==
- LK_SHARERS_LOCK(1));
- if (atomic_fcmpset_rel_ptr(&lk->lk_lock, xp,
- LK_UNLOCKED))
- return (true);
- continue;
- }
break;
}
return (false);
@@ -574,7 +567,7 @@ lockmgr_slock_hard(struct lock *lk, u_int flags, struc
WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER,
file, line, flags & LK_INTERLOCK ? ilk : NULL);
for (;;) {
- if (lockmgr_slock_try(lk, &x, flags))
+ if (lockmgr_slock_try(lk, &x, flags, false))
break;
#ifdef HWPMC_HOOKS
PMC_SOFT_CALL( , , lock, failed);
@@ -617,7 +610,7 @@ retry_sleepq:
* if the lock can be acquired in shared mode, try
* again.
*/
- if (LK_CAN_SHARE(x, flags)) {
+ if (LK_CAN_SHARE(x, flags, false)) {
sleepq_release(&lk->lock_object);
continue;
}
@@ -932,7 +925,7 @@ lockmgr_lock_fast_path(struct lock *lk, u_int flags, s
file, line, flags & LK_INTERLOCK ? ilk : NULL);
if (__predict_false(lk->lock_object.lo_flags & LK_NOSHARE))
break;
- if (lockmgr_slock_try(lk, &x, flags)) {
+ if (lockmgr_slock_try(lk, &x, flags, true)) {
lockmgr_note_shared_acquire(lk, 0, 0,
file, line, flags);
locked = true;
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