diff options
Diffstat (limited to 'usr/src/lib/varpd/svp/common/libvarpd_svp_timer.c')
| -rw-r--r-- | usr/src/lib/varpd/svp/common/libvarpd_svp_timer.c | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/usr/src/lib/varpd/svp/common/libvarpd_svp_timer.c b/usr/src/lib/varpd/svp/common/libvarpd_svp_timer.c new file mode 100644 index 0000000000..10b02748f3 --- /dev/null +++ b/usr/src/lib/varpd/svp/common/libvarpd_svp_timer.c @@ -0,0 +1,150 @@ +/* + * This file and its contents are supplied under the terms of the + * Common Development and Distribution License ("CDDL"), version 1.0. + * You may only use this file in accordance with the terms of version + * 1.0 of the CDDL. + * + * A full copy of the text of the CDDL should have accompanied this + * source. A copy of the CDDL is also available via the Internet at + * http://www.illumos.org/license/CDDL. + */ + +/* + * Copyright 2015, Joyent, Inc. + */ + +#include <stddef.h> +#include <libvarpd_svp.h> + +/* + * svp timer backend + * + * This implements all of the logic of maintaining a timer for the svp backend. + * We have a timer that fires at a one second tick. We maintain all of our + * events in avl tree, sorted by the tick that they need to be processed at. + * + * For more information, see the big theory statement in + * lib/varpd/svp/common/libvarpd_svp.c. + */ + +int svp_tickrate = 1; +static svp_event_t svp_timer_event; +static mutex_t svp_timer_lock = ERRORCHECKMUTEX; +static cond_t svp_timer_cv = DEFAULTCV; +static avl_tree_t svp_timer_tree; +static uint64_t svp_timer_nticks; + +static int +svp_timer_comparator(const void *l, const void *r) +{ + const svp_timer_t *lt, *rt; + + lt = l; + rt = r; + + if (lt->st_expire > rt->st_expire) + return (1); + else if (lt->st_expire < rt->st_expire) + return (-1); + + /* + * Multiple timers can have the same delivery time, so sort within that + * by the address of the timer itself. + */ + if ((uintptr_t)lt > (uintptr_t)rt) + return (1); + else if ((uintptr_t)lt < (uintptr_t)rt) + return (-1); + + return (0); +} + +/* ARGSUSED */ +static void +svp_timer_tick(port_event_t *pe, void *arg) +{ + mutex_enter(&svp_timer_lock); + svp_timer_nticks++; + + for (;;) { + svp_timer_t *t; + + t = avl_first(&svp_timer_tree); + if (t == NULL || t->st_expire > svp_timer_nticks) + break; + + avl_remove(&svp_timer_tree, t); + + /* + * We drop this while performing an operation so that way state + * can advance in the face of a long-running callback. + */ + t->st_delivering = B_TRUE; + mutex_exit(&svp_timer_lock); + t->st_func(t->st_arg); + mutex_enter(&svp_timer_lock); + t->st_delivering = B_FALSE; + (void) cond_broadcast(&svp_timer_cv); + if (t->st_oneshot == B_FALSE) { + t->st_expire += t->st_value; + avl_add(&svp_timer_tree, t); + } + } + mutex_exit(&svp_timer_lock); +} + +void +svp_timer_add(svp_timer_t *stp) +{ + if (stp->st_value == 0) + libvarpd_panic("tried to add svp timer with zero value"); + + mutex_enter(&svp_timer_lock); + stp->st_delivering = B_FALSE; + stp->st_expire = svp_timer_nticks + stp->st_value; + avl_add(&svp_timer_tree, stp); + mutex_exit(&svp_timer_lock); +} + +void +svp_timer_remove(svp_timer_t *stp) +{ + mutex_enter(&svp_timer_lock); + + /* + * If the event in question is not currently being delivered, then we + * can stop it before it next fires. If it is currently being delivered, + * we need to wait for that to finish. Because we hold the timer lock, + * we know that it cannot be rearmed. Therefore, we make sure the one + * shot is set to zero, and wait until it's no longer set to delivering. + */ + if (stp->st_delivering == B_FALSE) { + avl_remove(&svp_timer_tree, stp); + mutex_exit(&svp_timer_lock); + return; + } + + stp->st_oneshot = B_TRUE; + while (stp->st_delivering == B_TRUE) + (void) cond_wait(&svp_timer_cv, &svp_timer_lock); + + mutex_exit(&svp_timer_lock); +} + +int +svp_timer_init(void) +{ + int ret; + + svp_timer_event.se_func = svp_timer_tick; + svp_timer_event.se_arg = NULL; + + avl_create(&svp_timer_tree, svp_timer_comparator, sizeof (svp_timer_t), + offsetof(svp_timer_t, st_link)); + + if ((ret = svp_event_timer_init(&svp_timer_event)) != 0) { + avl_destroy(&svp_timer_tree); + } + + return (ret); +} |