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Handle PCATCH in blockcount_sleep() so it can be interrupted.

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blockcount_wait() still unconditionally waits for the count to reach
zero before returning.

Tested by:	pho (a larger patch)
Reviewed by:	kib
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D24513
This commit is contained in:
Mark Johnston 2020-04-21 17:13:06 +00:00
parent 8e3442b724
commit 304dcfb0d8
2 changed files with 22 additions and 13 deletions
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31
sys/kern/kern_synch.c
View File

@ -400,12 +400,12 @@ _blockcount_wakeup(blockcount_t *bc, u_int old)
}
/*
* Wait for a wakeup. This does not guarantee that the count is still zero on
* return and may be subject to transient wakeups. Callers wanting a precise
* answer should use blockcount_wait() with an interlock.
* Wait for a wakeup or a signal. This does not guarantee that the count is
* still zero on return. Callers wanting a precise answer should use
* blockcount_wait() with an interlock.
*
* Return 0 if there is no work to wait for, and 1 if we slept waiting for work
* to complete. In the latter case the counter value must be re-read.
* If there is no work to wait for, return 0. If the sleep was interrupted by a
* signal, return EINTR or ERESTART, and return EAGAIN otherwise.
*/
int
_blockcount_sleep(blockcount_t *bc, struct lock_object *lock, const char *wmesg,
@ -415,10 +415,15 @@ _blockcount_sleep(blockcount_t *bc, struct lock_object *lock, const char *wmesg,
uintptr_t lock_state;
u_int old;
int ret;
bool catch, drop;
KASSERT(lock != &Giant.lock_object,
("%s: cannot use Giant as the interlock", __func__));
catch = (prio & PCATCH) != 0;
drop = (prio & PDROP) != 0;
prio &= PRIMASK;
/*
* Synchronize with the fence in blockcount_release(). If we end up
* waiting, the sleepqueue lock acquisition will provide the required
@ -428,7 +433,7 @@ _blockcount_sleep(blockcount_t *bc, struct lock_object *lock, const char *wmesg,
* ourselves to sleep to avoid jumping ahead.
*/
if (atomic_load_acq_int(&bc->__count) == 0) {
if (lock != NULL && (prio & PDROP) != 0)
if (lock != NULL && drop)
LOCK_CLASS(lock)->lc_unlock(lock);
return (0);
}
@ -439,23 +444,27 @@ _blockcount_sleep(blockcount_t *bc, struct lock_object *lock, const char *wmesg,
if (lock != NULL)
lock_state = LOCK_CLASS(lock)->lc_unlock(lock);
old = blockcount_read(bc);
ret = 0;
do {
if (_BLOCKCOUNT_COUNT(old) == 0) {
sleepq_release(wchan);
ret = 0;
goto out;
}
if (_BLOCKCOUNT_WAITERS(old))
break;
} while (!atomic_fcmpset_int(&bc->__count, &old,
old | _BLOCKCOUNT_WAITERS_FLAG));
sleepq_add(wchan, NULL, wmesg, 0, 0);
sleepq_wait(wchan, prio);
ret = 1;
sleepq_add(wchan, NULL, wmesg, catch ? SLEEPQ_INTERRUPTIBLE : 0, 0);
if (catch)
ret = sleepq_wait_sig(wchan, prio);
else
sleepq_wait(wchan, prio);
if (ret == 0)
ret = EAGAIN;
out:
PICKUP_GIANT();
if (lock != NULL && (prio & PDROP) == 0)
if (lock != NULL && !drop)
LOCK_CLASS(lock)->lc_lock(lock, lock_state);
return (ret);

4
sys/sys/blockcount.h
View File

@ -80,9 +80,9 @@ static __inline void
_blockcount_wait(blockcount_t *bc, struct lock_object *lo, const char *wmesg,
int prio)
{
KASSERT((prio & PDROP) == 0, ("%s: invalid prio %x", __func__, prio));
KASSERT((prio & ~PRIMASK) == 0, ("%s: invalid prio %x", __func__, prio));
while (_blockcount_sleep(bc, lo, wmesg, prio) != 0)
while (_blockcount_sleep(bc, lo, wmesg, prio) == EAGAIN)
;
}