1 /* 2 * Copyright (c) 2001 Jake Burkholder <jake@FreeBSD.org> 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, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 * 26 * $FreeBSD$ 27 */ 28 29 #include <sys/param.h> 30 #include <sys/systm.h> 31 #include <sys/kernel.h> 32 #include <sys/ktr.h> 33 #include <sys/lock.h> 34 #include <sys/mutex.h> 35 #include <sys/proc.h> 36 #include <sys/queue.h> 37 38 /* 39 * Global run queue. 40 */ 41 static struct runq runq; 42 SYSINIT(runq, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, runq_init, &runq) 43 44 /* 45 * Wrappers which implement old interface; act on global run queue. 46 */ 47 48 struct thread * 49 choosethread(void) 50 { 51 return (runq_choose(&runq)->ke_thread); 52 } 53 54 int 55 procrunnable(void) 56 { 57 return runq_check(&runq); 58 } 59 60 void 61 remrunqueue(struct thread *td) 62 { 63 runq_remove(&runq, td->td_kse); 64 } 65 66 void 67 setrunqueue(struct thread *td) 68 { 69 runq_add(&runq, td->td_kse); 70 } 71 72 /* 73 * Clear the status bit of the queue corresponding to priority level pri, 74 * indicating that it is empty. 75 */ 76 static __inline void 77 runq_clrbit(struct runq *rq, int pri) 78 { 79 struct rqbits *rqb; 80 81 rqb = &rq->rq_status; 82 CTR4(KTR_RUNQ, "runq_clrbit: bits=%#x %#x bit=%#x word=%d", 83 rqb->rqb_bits[RQB_WORD(pri)], 84 rqb->rqb_bits[RQB_WORD(pri)] & ~RQB_BIT(pri), 85 RQB_BIT(pri), RQB_WORD(pri)); 86 rqb->rqb_bits[RQB_WORD(pri)] &= ~RQB_BIT(pri); 87 } 88 89 /* 90 * Find the index of the first non-empty run queue. This is done by 91 * scanning the status bits, a set bit indicates a non-empty queue. 92 */ 93 static __inline int 94 runq_findbit(struct runq *rq) 95 { 96 struct rqbits *rqb; 97 int pri; 98 int i; 99 100 rqb = &rq->rq_status; 101 for (i = 0; i < RQB_LEN; i++) 102 if (rqb->rqb_bits[i]) { 103 pri = (RQB_FFS(rqb->rqb_bits[i]) - 1) + 104 (i << RQB_L2BPW); 105 CTR3(KTR_RUNQ, "runq_findbit: bits=%#x i=%d pri=%d", 106 rqb->rqb_bits[i], i, pri); 107 return (pri); 108 } 109 110 return (-1); 111 } 112 113 /* 114 * Set the status bit of the queue corresponding to priority level pri, 115 * indicating that it is non-empty. 116 */ 117 static __inline void 118 runq_setbit(struct runq *rq, int pri) 119 { 120 struct rqbits *rqb; 121 122 rqb = &rq->rq_status; 123 CTR4(KTR_RUNQ, "runq_setbit: bits=%#x %#x bit=%#x word=%d", 124 rqb->rqb_bits[RQB_WORD(pri)], 125 rqb->rqb_bits[RQB_WORD(pri)] | RQB_BIT(pri), 126 RQB_BIT(pri), RQB_WORD(pri)); 127 rqb->rqb_bits[RQB_WORD(pri)] |= RQB_BIT(pri); 128 } 129 130 #ifdef INVARIANT_SUPPORT 131 /* 132 * Return true if the specified process is already in the run queue. 133 */ 134 static __inline int 135 runq_find(struct runq *rq, struct kse *ke) 136 { 137 struct kse *ke2; 138 int i; 139 140 mtx_assert(&sched_lock, MA_OWNED); 141 for (i = 0; i < RQB_LEN; i++) 142 TAILQ_FOREACH(ke2, &rq->rq_queues[i], ke_procq) 143 if (ke2 == ke) 144 return 1; 145 return 0; 146 } 147 #endif 148 149 /* 150 * Add the process to the queue specified by its priority, and set the 151 * corresponding status bit. 152 */ 153 void 154 runq_add(struct runq *rq, struct kse *ke) 155 { 156 struct rqhead *rqh; 157 int pri; 158 159 struct ksegrp *kg = ke->ke_ksegrp; 160 #ifdef INVARIANTS 161 struct proc *p = ke->ke_proc; 162 #endif 163 if (ke->ke_flags & KEF_ONRUNQ) 164 return; 165 mtx_assert(&sched_lock, MA_OWNED); 166 KASSERT(p->p_stat == SRUN, ("runq_add: proc %p (%s) not SRUN", 167 p, p->p_comm)); 168 KASSERT(runq_find(rq, ke) == 0, 169 ("runq_add: proc %p (%s) already in run queue", ke, p->p_comm)); 170 pri = kg->kg_pri.pri_level / RQ_PPQ; 171 ke->ke_rqindex = pri; 172 runq_setbit(rq, pri); 173 rqh = &rq->rq_queues[pri]; 174 CTR4(KTR_RUNQ, "runq_add: p=%p pri=%d %d rqh=%p", 175 ke->ke_proc, kg->kg_pri.pri_level, pri, rqh); 176 TAILQ_INSERT_TAIL(rqh, ke, ke_procq); 177 ke->ke_flags |= KEF_ONRUNQ; 178 } 179 180 /* 181 * Return true if there are runnable processes of any priority on the run 182 * queue, false otherwise. Has no side effects, does not modify the run 183 * queue structure. 184 */ 185 int 186 runq_check(struct runq *rq) 187 { 188 struct rqbits *rqb; 189 int i; 190 191 rqb = &rq->rq_status; 192 for (i = 0; i < RQB_LEN; i++) 193 if (rqb->rqb_bits[i]) { 194 CTR2(KTR_RUNQ, "runq_check: bits=%#x i=%d", 195 rqb->rqb_bits[i], i); 196 return (1); 197 } 198 CTR0(KTR_RUNQ, "runq_check: empty"); 199 200 return (0); 201 } 202 203 /* 204 * Find and remove the highest priority process from the run queue. 205 * If there are no runnable processes, the per-cpu idle process is 206 * returned. Will not return NULL under any circumstances. 207 */ 208 struct kse * 209 runq_choose(struct runq *rq) 210 { 211 struct rqhead *rqh; 212 struct kse *ke; 213 int pri; 214 215 mtx_assert(&sched_lock, MA_OWNED); 216 if ((pri = runq_findbit(rq)) != -1) { 217 rqh = &rq->rq_queues[pri]; 218 ke = TAILQ_FIRST(rqh); 219 KASSERT(ke != NULL, ("runq_choose: no proc on busy queue")); 220 KASSERT(ke->ke_proc->p_stat == SRUN, 221 ("runq_choose: process %d(%s) in state %d", ke->ke_proc->p_pid, 222 ke->ke_proc->p_comm, ke->ke_proc->p_stat)); 223 CTR3(KTR_RUNQ, "runq_choose: pri=%d kse=%p rqh=%p", pri, ke, rqh); 224 TAILQ_REMOVE(rqh, ke, ke_procq); 225 if (TAILQ_EMPTY(rqh)) { 226 CTR0(KTR_RUNQ, "runq_choose: empty"); 227 runq_clrbit(rq, pri); 228 } 229 ke->ke_flags &= ~KEF_ONRUNQ; 230 return (ke); 231 } 232 CTR1(KTR_RUNQ, "runq_choose: idleproc pri=%d", pri); 233 234 return (PCPU_GET(idlethread)->td_kse); 235 } 236 237 /* 238 * Initialize a run structure. 239 */ 240 void 241 runq_init(struct runq *rq) 242 { 243 int i; 244 245 bzero(rq, sizeof *rq); 246 for (i = 0; i < RQ_NQS; i++) 247 TAILQ_INIT(&rq->rq_queues[i]); 248 } 249 250 /* 251 * Remove the process from the queue specified by its priority, and clear the 252 * corresponding status bit if the queue becomes empty. 253 */ 254 void 255 runq_remove(struct runq *rq, struct kse *ke) 256 { 257 #ifdef KTR 258 struct ksegrp *kg = ke->ke_ksegrp; 259 #endif 260 struct rqhead *rqh; 261 int pri; 262 263 if (!(ke->ke_flags & KEF_ONRUNQ)) 264 return; 265 mtx_assert(&sched_lock, MA_OWNED); 266 pri = ke->ke_rqindex; 267 rqh = &rq->rq_queues[pri]; 268 CTR4(KTR_RUNQ, "runq_remove: p=%p pri=%d %d rqh=%p", 269 ke, kg->kg_pri.pri_level, pri, rqh); 270 KASSERT(ke != NULL, ("runq_remove: no proc on busy queue")); 271 TAILQ_REMOVE(rqh, ke, ke_procq); 272 if (TAILQ_EMPTY(rqh)) { 273 CTR0(KTR_RUNQ, "runq_remove: empty"); 274 runq_clrbit(rq, pri); 275 } 276 ke->ke_flags &= ~KEF_ONRUNQ; 277 } 278