diff options
| author | Attilio Rao <attilio@FreeBSD.org> | 2009-09-09 09:17:31 +0000 |
|---|---|---|
| committer | Attilio Rao <attilio@FreeBSD.org> | 2009-09-09 09:17:31 +0000 |
| commit | db0c92ce82f76f9aa389bc2b0e76deee6a5009ab (patch) | |
| tree | f53b14eeeece3012fa6fba1d77e35a78198d9b39 /sys/kern/kern_lock.c | |
| parent | 6a89c3ede1df004863468a09fc885baa80e82937 (diff) | |
Notes
Diffstat (limited to 'sys/kern/kern_lock.c')
| -rw-r--r-- | sys/kern/kern_lock.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/sys/kern/kern_lock.c b/sys/kern/kern_lock.c index 29ae4accfa71..e6f2f5362494 100644 --- a/sys/kern/kern_lock.c +++ b/sys/kern/kern_lock.c @@ -467,7 +467,10 @@ __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, /* * If the owner is running on another CPU, spin until * the owner stops running or the state of the lock - * changes. + * changes. We need a double-state handle here + * because for a failed acquisition the lock can be + * either held in exclusive mode or shared mode + * (for the writer starvation avoidance technique). */ if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) == 0 && LK_HOLDER(x) != LK_KERNPROC) { @@ -491,8 +494,10 @@ __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, while (LK_HOLDER(lk->lk_lock) == (uintptr_t)owner && TD_IS_RUNNING(owner)) cpu_spinwait(); + GIANT_RESTORE(); + continue; } else if (LK_CAN_ADAPT(lk, flags) && - (x & LK_SHARE) !=0 && LK_SHARERS(x) && + (x & LK_SHARE) != 0 && LK_SHARERS(x) && spintries < alk_retries) { if (flags & LK_INTERLOCK) { class->lc_unlock(ilk); @@ -511,6 +516,7 @@ __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, break; cpu_spinwait(); } + GIANT_RESTORE(); if (i != alk_loops) continue; } @@ -704,6 +710,8 @@ __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, while (LK_HOLDER(lk->lk_lock) == (uintptr_t)owner && TD_IS_RUNNING(owner)) cpu_spinwait(); + GIANT_RESTORE(); + continue; } else if (LK_CAN_ADAPT(lk, flags) && (x & LK_SHARE) != 0 && LK_SHARERS(x) && spintries < alk_retries) { @@ -727,6 +735,7 @@ __lockmgr_args(struct lock *lk, u_int flags, struct lock_object *ilk, break; cpu_spinwait(); } + GIANT_RESTORE(); if (i != alk_loops) continue; } |