projects / urcu.git / blame
| Commit | Line | Data |
|---|---|---|
| acdb82a2 MJ |
1 | // SPDX-FileCopyrightText: 2023 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 2 | // | |
| 3 | // SPDX-License-Identifier: LGPL-2.1-or-later | |
| 4 | ||
| 111bda8f | 5 | /* |
| 111bda8f | 6 | * Userspace RCU library - Grace period polling API |
| 111bda8f MD |
7 | */ |
| 8 | ||
| 9 | #include <pthread.h> | |
| 10 | #include <stdbool.h> | |
| 11 | ||
| 12 | #include <urcu/urcu-poll.h> | |
| 13 | #include <urcu/call-rcu.h> | |
| 14 | ||
| 15 | struct urcu_poll_worker_state { | |
| 16 | struct urcu_gp_poll_state current_state; | |
| 17 | struct urcu_gp_poll_state latest_target; /* Most recent snapshot taken */ | |
| 18 | struct rcu_head rcu_head; | |
| 19 | pthread_mutex_t lock; | |
| 20 | bool active; | |
| 21 | }; | |
| 22 | ||
| 23 | static struct urcu_poll_worker_state poll_worker_gp_state = { | |
| 24 | .lock = PTHREAD_MUTEX_INITIALIZER, | |
| 25 | }; | |
| 26 | ||
| 27 | static | |
| 28 | void urcu_poll_worker_cb(struct rcu_head *head __attribute__((unused))) | |
| 29 | { | |
| 30 | mutex_lock(&poll_worker_gp_state.lock); | |
| 31 | /* A new grace period has been reached. */ | |
| 32 | poll_worker_gp_state.current_state.grace_period_id++; | |
| 33 | if ((long)(poll_worker_gp_state.latest_target.grace_period_id - poll_worker_gp_state.current_state.grace_period_id) >= 0) { | |
| 34 | /* Need to re-queue. */ | |
| 35 | call_rcu(&poll_worker_gp_state.rcu_head, urcu_poll_worker_cb); | |
| 36 | } else { | |
| 37 | /* No user waiting for a target grace period. */ | |
| 38 | poll_worker_gp_state.active = false; | |
| 39 | } | |
| 40 | mutex_unlock(&poll_worker_gp_state.lock); | |
| 41 | } | |
| 42 | ||
| 43 | /* | |
| 44 | * Start polling on grace period. If no worker is currently active, | |
| 45 | * snapshot the current value and start a worker callback. If the worker | |
| 46 | * is currently active, snapshot the current value + 1, and set this | |
| 47 | * value as the latest snapshot, which will cause the worker to re-queue | |
| 48 | * itself with call_rcu to issue one more grace period. | |
| 49 | * | |
| 50 | * Because it uses call_rcu, it needs to be called from a registered RCU | |
| 51 | * thread. | |
| 52 | */ | |
| 53 | struct urcu_gp_poll_state start_poll_synchronize_rcu(void) | |
| 54 | { | |
| 55 | struct urcu_gp_poll_state new_target_gp_state; | |
| 56 | bool was_active = false; | |
| 57 | ||
| 58 | mutex_lock(&poll_worker_gp_state.lock); | |
| 59 | new_target_gp_state.grace_period_id = poll_worker_gp_state.current_state.grace_period_id; | |
| 60 | was_active = poll_worker_gp_state.active; | |
| 61 | if (!was_active) | |
| 62 | poll_worker_gp_state.active = true; | |
| 63 | else | |
| 64 | new_target_gp_state.grace_period_id++; | |
| 65 | poll_worker_gp_state.latest_target.grace_period_id = new_target_gp_state.grace_period_id; | |
| 66 | if (!was_active) | |
| 67 | call_rcu(&poll_worker_gp_state.rcu_head, urcu_poll_worker_cb); | |
| 68 | mutex_unlock(&poll_worker_gp_state.lock); | |
| 69 | return new_target_gp_state; | |
| 70 | } | |
| 71 | ||
| 72 | /* | |
| 73 | * Poll the grace period state. Return true if quiescence was reached | |
| 74 | * since the snapshot was taken, return false if quiescence was not | |
| 75 | * reached since snapshot. | |
| 76 | */ | |
| 77 | bool poll_state_synchronize_rcu(struct urcu_gp_poll_state target_gp_state) | |
| 78 | { | |
| 79 | bool target_gp_reached = false; | |
| 80 | ||
| 81 | mutex_lock(&poll_worker_gp_state.lock); | |
| 82 | if ((long)(target_gp_state.grace_period_id - poll_worker_gp_state.current_state.grace_period_id) < 0) | |
| 83 | target_gp_reached = true; | |
| 84 | mutex_unlock(&poll_worker_gp_state.lock); | |
| 85 | return target_gp_reached; | |
| 86 | } |