/* SPDX-License-Identifier: GPL-2.0-only */ #include <timer.h> #define MAX_TIMER_QUEUE_ENTRIES 64 /* The timer queue is implemented using a min heap. Therefore the first * element is the one with smallest time to expiration. */ struct timer_queue { int num_entries; int max_entries; struct timeout_callback *queue[MAX_TIMER_QUEUE_ENTRIES]; }; static struct timer_queue global_timer_queue = { .num_entries = 0, .max_entries = MAX_TIMER_QUEUE_ENTRIES, .queue = { 0 }, }; static inline int timer_queue_empty(struct timer_queue *tq) { return tq->num_entries == 0; } static inline int timer_queue_full(struct timer_queue *tq) { return tq->num_entries == tq->max_entries; } static inline struct timeout_callback *timer_queue_head(struct timer_queue *tq) { if (timer_queue_empty(tq)) return NULL; return tq->queue[0]; } static int timer_queue_insert(struct timer_queue *tq, struct timeout_callback *tocb) { int index; /* No more slots. */ if (timer_queue_full(tq)) return -1; index = tq->num_entries; tq->num_entries++; tq->queue[index] = tocb; while (index != 0) { struct timeout_callback *parent; int parent_index; parent_index = (index - 1) / 2; parent = tq->queue[parent_index]; /* All other ancestors are less than or equal to the current. */ if (mono_time_cmp(&parent->expiration, &tocb->expiration) <= 0) break; /* The parent is greater than current. Swap them. */ tq->queue[parent_index] = tocb; tq->queue[index] = parent; index = parent_index; } return 0; } /* Get the index containing the entry with smallest value. */ static int timer_queue_min_child_index(struct timer_queue *tq, int index) { int left_child_index; int right_child_index; left_child_index = 2 * index + 1; if (left_child_index >= tq->num_entries) return -1; right_child_index = left_child_index + 1; if (right_child_index >= tq->num_entries) return left_child_index; if (mono_time_cmp(&tq->queue[left_child_index]->expiration, &tq->queue[right_child_index]->expiration) < 0) { return left_child_index; } return right_child_index; } static void timer_queue_remove_head(struct timer_queue *tq) { int index; struct timeout_callback *tocb; /* In order to remove the head the deepest child is replaced in the * head slot and bubbled down the tree. */ tq->num_entries--; tocb = tq->queue[tq->num_entries]; tq->queue[0] = tocb; index = 0; while (1) { int min_child_index; struct timeout_callback *child; min_child_index = timer_queue_min_child_index(tq, index); /* No more entries to compare against. */ if (min_child_index < 0) break; child = tq->queue[min_child_index]; /* Current index is the correct place since it is smaller or * equal to the smallest child. */ if (mono_time_cmp(&tocb->expiration, &child->expiration) <= 0) break; /* Need to swap with smallest child. */ tq->queue[min_child_index] = tocb; tq->queue[index] = child; index = min_child_index; } } static struct timeout_callback * timer_queue_expired(struct timer_queue *tq, struct mono_time *current_time) { struct timeout_callback *tocb; tocb = timer_queue_head(tq); if (tocb == NULL) return NULL; /* The timeout callback hasn't expired yet. */ if (mono_time_before(current_time, &tocb->expiration)) return NULL; timer_queue_remove_head(tq); return tocb; } int timer_sched_callback(struct timeout_callback *tocb, unsigned long us) { struct mono_time current_time; if ((long)us < 0) return -1; timer_monotonic_get(¤t_time); tocb->expiration = current_time; mono_time_add_usecs(&tocb->expiration, us); /* The expiration overflowed. */ if (us != 0 && !mono_time_before(¤t_time, &tocb->expiration)) return -1; return timer_queue_insert(&global_timer_queue, tocb); } int timers_run(void) { struct timeout_callback *tocb; struct mono_time current_time; timer_monotonic_get(¤t_time); tocb = timer_queue_expired(&global_timer_queue, ¤t_time); if (tocb != NULL) tocb->callback(tocb); return !timer_queue_empty(&global_timer_queue); }