svn commit: r360163 - in head/sys: kern sys
Mark Johnston
markj at FreeBSD.org
Tue Apr 21 17:13:07 UTC 2020
Author: markj
Date: Tue Apr 21 17:13:06 2020
New Revision: 360163
URL: https://svnweb.freebsd.org/changeset/base/360163
Log:
Handle PCATCH in blockcount_sleep() so it can be interrupted.
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
Modified:
head/sys/kern/kern_synch.c
head/sys/sys/blockcount.h
Modified: head/sys/kern/kern_synch.c
==============================================================================
--- head/sys/kern/kern_synch.c Tue Apr 21 17:07:02 2020 (r360162)
+++ head/sys/kern/kern_synch.c Tue Apr 21 17:13:06 2020 (r360163)
@@ -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
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
* 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
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);
Modified: head/sys/sys/blockcount.h
==============================================================================
--- head/sys/sys/blockcount.h Tue Apr 21 17:07:02 2020 (r360162)
+++ head/sys/sys/blockcount.h Tue Apr 21 17:13:06 2020 (r360163)
@@ -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)
;
}
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