diff options
Diffstat (limited to 'freebsd/sys/kern/kern_synch.c')
| -rw-r--r-- | freebsd/sys/kern/kern_synch.c | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/freebsd/sys/kern/kern_synch.c b/freebsd/sys/kern/kern_synch.c index 2597f91d..7d24c248 100644 --- a/freebsd/sys/kern/kern_synch.c +++ b/freebsd/sys/kern/kern_synch.c @@ -54,6 +54,7 @@ __FBSDID("$FreeBSD$"); #include <sys/mutex.h> #include <sys/proc.h> #include <sys/resourcevar.h> +#include <sys/refcount.h> #include <sys/sched.h> #include <sys/sdt.h> #include <sys/signalvar.h> @@ -366,6 +367,75 @@ pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags) } /* + * Potentially release the last reference for refcount. Check for + * unlikely conditions and signal the caller as to whether it was + * the final ref. + */ +bool +refcount_release_last(volatile u_int *count, u_int n, u_int old) +{ + u_int waiter; + + waiter = old & REFCOUNT_WAITER; + old = REFCOUNT_COUNT(old); + if (__predict_false(n > old || REFCOUNT_SATURATED(old))) { + /* + * Avoid multiple destructor invocations if underflow occurred. + * This is not perfect since the memory backing the containing + * object may already have been reallocated. + */ + _refcount_update_saturated(count); + return (false); + } + + /* + * Attempt to atomically clear the waiter bit. Wakeup waiters + * if we are successful. + */ + if (waiter != 0 && atomic_cmpset_int(count, REFCOUNT_WAITER, 0)) + wakeup(__DEVOLATILE(u_int *, count)); + + /* + * Last reference. Signal the user to call the destructor. + * + * Ensure that the destructor sees all updates. The fence_rel + * at the start of refcount_releasen synchronizes with this fence. + */ + atomic_thread_fence_acq(); + return (true); +} + +/* + * Wait for a refcount wakeup. This does not guarantee that the ref is still + * zero on return and may be subject to transient wakeups. Callers wanting + * a precise answer should use refcount_wait(). + */ +void +refcount_sleep(volatile u_int *count, const char *wmesg, int pri) +{ + void *wchan; + u_int old; + + if (REFCOUNT_COUNT(*count) == 0) + return; + wchan = __DEVOLATILE(void *, count); + sleepq_lock(wchan); + old = *count; + for (;;) { + if (REFCOUNT_COUNT(old) == 0) { + sleepq_release(wchan); + return; + } + if (old & REFCOUNT_WAITER) + break; + if (atomic_fcmpset_int(count, &old, old | REFCOUNT_WAITER)) + break; + } + sleepq_add(wchan, NULL, wmesg, 0, 0); + sleepq_wait(wchan, pri); +} + +/* * Make all threads sleeping on the specified identifier runnable. */ void @@ -402,6 +472,19 @@ wakeup_one(void *ident) kick_proc0(); } +void +wakeup_any(void *ident) +{ + int wakeup_swapper; + + sleepq_lock(ident); + wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_UNFAIR, + 0, 0); + sleepq_release(ident); + if (wakeup_swapper) + kick_proc0(); +} + #ifndef __rtems__ static void kdb_switch(void) |