1 /*- 2 * Copyright (c) 2017 Hans Petter Selasky 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice unmodified, this list of conditions, and the following 10 * disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include <sys/cdefs.h> 28 __FBSDID("$FreeBSD$"); 29 30 #include <sys/types.h> 31 #include <sys/malloc.h> 32 #include <sys/gtaskqueue.h> 33 #include <sys/proc.h> 34 #include <sys/sched.h> 35 36 #include <linux/compiler.h> 37 #include <linux/interrupt.h> 38 #include <linux/compat.h> 39 40 #define TASKLET_ST_IDLE 0 41 #define TASKLET_ST_BUSY 1 42 #define TASKLET_ST_EXEC 2 43 #define TASKLET_ST_LOOP 3 44 45 #define TASKLET_ST_CMPSET(ts, old, new) \ 46 atomic_cmpset_int((volatile u_int *)&(ts)->tasklet_state, old, new) 47 48 #define TASKLET_ST_SET(ts, new) \ 49 WRITE_ONCE(*(volatile u_int *)&(ts)->tasklet_state, new) 50 51 #define TASKLET_ST_GET(ts) \ 52 READ_ONCE(*(volatile u_int *)&(ts)->tasklet_state) 53 54 struct tasklet_worker { 55 struct mtx mtx; 56 TAILQ_HEAD(tasklet_list, tasklet_struct) head; 57 struct grouptask gtask; 58 } __aligned(CACHE_LINE_SIZE); 59 60 #define TASKLET_WORKER_LOCK(tw) mtx_lock(&(tw)->mtx) 61 #define TASKLET_WORKER_UNLOCK(tw) mtx_unlock(&(tw)->mtx) 62 63 DPCPU_DEFINE_STATIC(struct tasklet_worker, tasklet_worker); 64 65 static void 66 tasklet_handler(void *arg) 67 { 68 struct tasklet_worker *tw = (struct tasklet_worker *)arg; 69 struct tasklet_struct *ts; 70 struct tasklet_struct *last; 71 72 linux_set_current(curthread); 73 74 TASKLET_WORKER_LOCK(tw); 75 last = TAILQ_LAST(&tw->head, tasklet_list); 76 while (1) { 77 ts = TAILQ_FIRST(&tw->head); 78 if (ts == NULL) 79 break; 80 TAILQ_REMOVE(&tw->head, ts, entry); 81 82 if (!atomic_read(&ts->count)) { 83 TASKLET_WORKER_UNLOCK(tw); 84 do { 85 /* reset executing state */ 86 TASKLET_ST_SET(ts, TASKLET_ST_EXEC); 87 88 ts->func(ts->data); 89 90 } while (TASKLET_ST_CMPSET(ts, TASKLET_ST_EXEC, 91 TASKLET_ST_IDLE) == 0); 92 TASKLET_WORKER_LOCK(tw); 93 } else { 94 TAILQ_INSERT_TAIL(&tw->head, ts, entry); 95 } 96 if (ts == last) 97 break; 98 } 99 TASKLET_WORKER_UNLOCK(tw); 100 } 101 102 static void 103 tasklet_subsystem_init(void *arg __unused) 104 { 105 struct tasklet_worker *tw; 106 char buf[32]; 107 int i; 108 109 CPU_FOREACH(i) { 110 if (CPU_ABSENT(i)) 111 continue; 112 113 tw = DPCPU_ID_PTR(i, tasklet_worker); 114 115 mtx_init(&tw->mtx, "linux_tasklet", NULL, MTX_DEF); 116 TAILQ_INIT(&tw->head); 117 GROUPTASK_INIT(&tw->gtask, 0, tasklet_handler, tw); 118 snprintf(buf, sizeof(buf), "softirq%d", i); 119 taskqgroup_attach_cpu(qgroup_softirq, &tw->gtask, 120 "tasklet", i, NULL, NULL, buf); 121 } 122 } 123 SYSINIT(linux_tasklet, SI_SUB_TASKQ, SI_ORDER_THIRD, tasklet_subsystem_init, NULL); 124 125 static void 126 tasklet_subsystem_uninit(void *arg __unused) 127 { 128 struct tasklet_worker *tw; 129 int i; 130 131 CPU_FOREACH(i) { 132 if (CPU_ABSENT(i)) 133 continue; 134 135 tw = DPCPU_ID_PTR(i, tasklet_worker); 136 137 taskqgroup_detach(qgroup_softirq, &tw->gtask); 138 mtx_destroy(&tw->mtx); 139 } 140 } 141 SYSUNINIT(linux_tasklet, SI_SUB_TASKQ, SI_ORDER_THIRD, tasklet_subsystem_uninit, NULL); 142 143 void 144 tasklet_init(struct tasklet_struct *ts, 145 tasklet_func_t *func, unsigned long data) 146 { 147 ts->entry.tqe_prev = NULL; 148 ts->entry.tqe_next = NULL; 149 ts->func = func; 150 ts->data = data; 151 atomic_set_int(&ts->tasklet_state, TASKLET_ST_IDLE); 152 atomic_set(&ts->count, 0); 153 } 154 155 void 156 local_bh_enable(void) 157 { 158 sched_unpin(); 159 } 160 161 void 162 local_bh_disable(void) 163 { 164 sched_pin(); 165 } 166 167 void 168 tasklet_schedule(struct tasklet_struct *ts) 169 { 170 171 /* tasklet is paused */ 172 if (atomic_read(&ts->count)) 173 return; 174 175 if (TASKLET_ST_CMPSET(ts, TASKLET_ST_EXEC, TASKLET_ST_LOOP)) { 176 /* tasklet_handler() will loop */ 177 } else if (TASKLET_ST_CMPSET(ts, TASKLET_ST_IDLE, TASKLET_ST_BUSY)) { 178 struct tasklet_worker *tw; 179 180 tw = &DPCPU_GET(tasklet_worker); 181 182 /* tasklet_handler() was not queued */ 183 TASKLET_WORKER_LOCK(tw); 184 /* enqueue tasklet */ 185 TAILQ_INSERT_TAIL(&tw->head, ts, entry); 186 /* schedule worker */ 187 GROUPTASK_ENQUEUE(&tw->gtask); 188 TASKLET_WORKER_UNLOCK(tw); 189 } else { 190 /* 191 * tasklet_handler() is already executing 192 * 193 * If the state is neither EXEC nor IDLE, it is either 194 * LOOP or BUSY. If the state changed between the two 195 * CMPSET's above the only possible transitions by 196 * elimination are LOOP->EXEC and BUSY->EXEC. If a 197 * EXEC->LOOP transition was missed that is not a 198 * problem because the callback function is then 199 * already about to be called again. 200 */ 201 } 202 } 203 204 void 205 tasklet_kill(struct tasklet_struct *ts) 206 { 207 208 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "tasklet_kill() can sleep"); 209 210 /* wait until tasklet is no longer busy */ 211 while (TASKLET_ST_GET(ts) != TASKLET_ST_IDLE) 212 pause("W", 1); 213 } 214 215 void 216 tasklet_enable(struct tasklet_struct *ts) 217 { 218 219 atomic_dec(&ts->count); 220 } 221 222 void 223 tasklet_disable(struct tasklet_struct *ts) 224 { 225 226 atomic_inc(&ts->count); 227 tasklet_unlock_wait(ts); 228 } 229 230 int 231 tasklet_trylock(struct tasklet_struct *ts) 232 { 233 234 return (TASKLET_ST_CMPSET(ts, TASKLET_ST_IDLE, TASKLET_ST_BUSY)); 235 } 236 237 void 238 tasklet_unlock(struct tasklet_struct *ts) 239 { 240 241 TASKLET_ST_SET(ts, TASKLET_ST_IDLE); 242 } 243 244 void 245 tasklet_unlock_wait(struct tasklet_struct *ts) 246 { 247 248 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "tasklet_kill() can sleep"); 249 250 /* wait until tasklet is no longer busy */ 251 while (TASKLET_ST_GET(ts) != TASKLET_ST_IDLE) 252 pause("W", 1); 253 } 254