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Provide an API for interlocked refcount sleeps.

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Reviewed by:	kib, markj
Differential Revision:	https://reviews.freebsd.org/D22908
This commit is contained in:
Jeff Roberson 2020-01-19 18:18:17 +00:00
parent 28479aaae2
commit 811d05fcb7
2 changed files with 24 additions and 3 deletions
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10
sys/kern/kern_synch.c
View File

@ -381,15 +381,21 @@ refcount_release_last(volatile u_int *count, u_int n, u_int old)
* a precise answer should use refcount_wait().
*/
void
refcount_sleep(volatile u_int *count, const char *wmesg, int pri)
_refcount_sleep(volatile u_int *count, struct lock_object *lock,
const char *wmesg, int pri)
{
void *wchan;
u_int old;
if (REFCOUNT_COUNT(*count) == 0)
if (REFCOUNT_COUNT(*count) == 0) {
if (lock != NULL)
LOCK_CLASS(lock)->lc_unlock(lock);
return;
}
wchan = __DEVOLATILE(void *, count);
sleepq_lock(wchan);
if (lock != NULL)
LOCK_CLASS(lock)->lc_unlock(lock);
old = *count;
for (;;) {
if (REFCOUNT_COUNT(old) == 0) {

17
sys/sys/refcount.h
View File

@ -46,7 +46,6 @@
#define REFCOUNT_COUNT(x) ((x) & ~REFCOUNT_WAITER)
bool refcount_release_last(volatile u_int *count, u_int n, u_int old);
void refcount_sleep(volatile u_int *count, const char *wmesg, int prio);
/*
* Attempt to handle reference count overflow and underflow. Force the counter
@ -135,6 +134,21 @@ refcount_release(volatile u_int *count)
return (refcount_releasen(count, 1));
}
#ifdef _KERNEL
struct lock_object;
void _refcount_sleep(volatile u_int *count, struct lock_object *,
const char *wmesg, int prio);
static __inline void
refcount_sleep(volatile u_int *count, const char *wmesg, int prio)
{
_refcount_sleep(count, NULL, wmesg, prio);
}
#define refcount_sleep_interlock(count, lock, wmesg, prio) \
_refcount_sleep((count), (struct lock_object *)(lock), (wmesg), (prio))
static __inline void
refcount_wait(volatile u_int *count, const char *wmesg, int prio)
{
@ -142,6 +156,7 @@ refcount_wait(volatile u_int *count, const char *wmesg, int prio)
while (*count != 0)
refcount_sleep(count, wmesg, prio);
}
#endif
/*
* This functions returns non-zero if the refcount was