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 taskqgroup_drain_all(qgroup_softirq); 132 133 CPU_FOREACH(i) { 134 if (CPU_ABSENT(i)) 135 continue; 136 137 tw = DPCPU_ID_PTR(i, tasklet_worker); 138 139 taskqgroup_detach(qgroup_softirq, &tw->gtask); 140 mtx_destroy(&tw->mtx); 141 } 142 } 143 SYSUNINIT(linux_tasklet, SI_SUB_TASKQ, SI_ORDER_THIRD, tasklet_subsystem_uninit, NULL); 144 145 void 146 tasklet_init(struct tasklet_struct *ts, 147 tasklet_func_t *func, unsigned long data) 148 { 149 ts->entry.tqe_prev = NULL; 150 ts->entry.tqe_next = NULL; 151 ts->func = func; 152 ts->data = data; 153 atomic_set_int(&ts->tasklet_state, TASKLET_ST_IDLE); 154 atomic_set(&ts->count, 0); 155 } 156 157 void 158 local_bh_enable(void) 159 { 160 sched_unpin(); 161 } 162 163 void 164 local_bh_disable(void) 165 { 166 sched_pin(); 167 } 168 169 void 170 tasklet_schedule(struct tasklet_struct *ts) 171 { 172 173 /* tasklet is paused */ 174 if (atomic_read(&ts->count)) 175 return; 176 177 if (TASKLET_ST_CMPSET(ts, TASKLET_ST_EXEC, TASKLET_ST_LOOP)) { 178 /* tasklet_handler() will loop */ 179 } else if (TASKLET_ST_CMPSET(ts, TASKLET_ST_IDLE, TASKLET_ST_BUSY)) { 180 struct tasklet_worker *tw; 181 182 tw = &DPCPU_GET(tasklet_worker); 183 184 /* tasklet_handler() was not queued */ 185 TASKLET_WORKER_LOCK(tw); 186 /* enqueue tasklet */ 187 TAILQ_INSERT_TAIL(&tw->head, ts, entry); 188 /* schedule worker */ 189 GROUPTASK_ENQUEUE(&tw->gtask); 190 TASKLET_WORKER_UNLOCK(tw); 191 } else { 192 /* 193 * tasklet_handler() is already executing 194 * 195 * If the state is neither EXEC nor IDLE, it is either 196 * LOOP or BUSY. If the state changed between the two 197 * CMPSET's above the only possible transitions by 198 * elimination are LOOP->EXEC and BUSY->EXEC. If a 199 * EXEC->LOOP transition was missed that is not a 200 * problem because the callback function is then 201 * already about to be called again. 202 */ 203 } 204 } 205 206 void 207 tasklet_kill(struct tasklet_struct *ts) 208 { 209 210 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "tasklet_kill() can sleep"); 211 212 /* wait until tasklet is no longer busy */ 213 while (TASKLET_ST_GET(ts) != TASKLET_ST_IDLE) 214 pause("W", 1); 215 } 216 217 void 218 tasklet_enable(struct tasklet_struct *ts) 219 { 220 221 atomic_dec(&ts->count); 222 } 223 224 void 225 tasklet_disable(struct tasklet_struct *ts) 226 { 227 228 atomic_inc(&ts->count); 229 tasklet_unlock_wait(ts); 230 } 231 232 void 233 tasklet_disable_nosync(struct tasklet_struct *ts) 234 { 235 atomic_inc(&ts->count); 236 barrier(); 237 } 238 239 int 240 tasklet_trylock(struct tasklet_struct *ts) 241 { 242 243 return (TASKLET_ST_CMPSET(ts, TASKLET_ST_IDLE, TASKLET_ST_BUSY)); 244 } 245 246 void 247 tasklet_unlock(struct tasklet_struct *ts) 248 { 249 250 TASKLET_ST_SET(ts, TASKLET_ST_IDLE); 251 } 252 253 void 254 tasklet_unlock_wait(struct tasklet_struct *ts) 255 { 256 257 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "tasklet_kill() can sleep"); 258 259 /* wait until tasklet is no longer busy */ 260 while (TASKLET_ST_GET(ts) != TASKLET_ST_IDLE) 261 pause("W", 1); 262 } 263