d/freebsd-nq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

lockmgr: fix upgrade

Browse Source 
TRYUPGRADE requests kept failing when they should not have due to wrong
macro used to count readers.

Fixes:	f6b091fbbd77cbb0 ("lockmgr: rewrite upgrade to stop always dropping the lock")
Noted by:	asomers
Differential Revision:	https://reviews.freebsd.org/D27947
This commit is contained in:
Mateusz Guzik 2021-01-07 07:45:49 +01:00
parent f635cef2a4
commit 38baca17e0
1 changed files with 4 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
sys/kern/kern_lock.c
View File

@ -984,17 +984,19 @@ lockmgr_upgrade(struct lock *lk, u_int flags, struct lock_object *ilk,
op = flags & LK_TYPE_MASK;
v = lockmgr_read_value(lk);
for (;;) {
if (LK_SHARERS_LOCK(v) > 1) {
if (LK_SHARERS(v) > 1) {
if (op == LK_TRYUPGRADE) {
LOCK_LOG2(lk, "%s: %p failed the nowait upgrade",
__func__, lk);
error = EBUSY;
goto out;
}
if (lockmgr_sunlock_try(lk, &v)) {
if (atomic_fcmpset_rel_ptr(&lk->lk_lock, &v,
v - LK_ONE_SHARER)) {
lockmgr_note_shared_release(lk, file, line);
goto out_xlock;
}
continue;
}
MPASS((v & ~LK_ALL_WAITERS) == LK_SHARERS_LOCK(1));