kern_kthread.c revision 1.48
1/* $NetBSD: kern_kthread.c,v 1.48 2023/07/17 10:55:27 riastradh Exp $ */ 2 3/*- 4 * Copyright (c) 1998, 1999, 2007, 2009, 2019 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, 9 * NASA Ames Research Center, and by Andrew Doran. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 22 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 23 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 24 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 25 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 26 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 27 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 28 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 29 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 30 * POSSIBILITY OF SUCH DAMAGE. 31 */ 32 33#include <sys/cdefs.h> 34__KERNEL_RCSID(0, "$NetBSD: kern_kthread.c,v 1.48 2023/07/17 10:55:27 riastradh Exp $"); 35 36#include <sys/param.h> 37#include <sys/cpu.h> 38#include <sys/systm.h> 39#include <sys/kernel.h> 40#include <sys/kthread.h> 41#include <sys/mutex.h> 42#include <sys/sched.h> 43#include <sys/kmem.h> 44#include <sys/msan.h> 45 46#include <uvm/uvm_extern.h> 47 48static kmutex_t kthread_lock; 49static kcondvar_t kthread_cv; 50 51void 52kthread_sysinit(void) 53{ 54 55 mutex_init(&kthread_lock, MUTEX_DEFAULT, IPL_NONE); 56 cv_init(&kthread_cv, "kthrwait"); 57} 58 59/* 60 * kthread_create: create a kernel thread, that is, system-only LWP. 61 */ 62int 63kthread_create(pri_t pri, int flag, struct cpu_info *ci, 64 void (*func)(void *), void *arg, lwp_t **lp, const char *fmt, ...) 65{ 66 lwp_t *l; 67 vaddr_t uaddr; 68 int error, lc; 69 va_list ap; 70 71 KASSERT((flag & KTHREAD_INTR) == 0 || (flag & KTHREAD_MPSAFE) != 0); 72 73 uaddr = uvm_uarea_system_alloc( 74 (flag & (KTHREAD_INTR|KTHREAD_IDLE)) == KTHREAD_IDLE ? ci : NULL); 75 if (uaddr == 0) { 76 return ENOMEM; 77 } 78 kmsan_orig((void *)uaddr, USPACE, KMSAN_TYPE_POOL, __RET_ADDR); 79 if ((flag & KTHREAD_TS) != 0) { 80 lc = SCHED_OTHER; 81 } else { 82 lc = SCHED_RR; 83 } 84 85 error = lwp_create(&lwp0, &proc0, uaddr, LWP_DETACHED, NULL, 86 0, func, arg, &l, lc, &lwp0.l_sigmask, &lwp0.l_sigstk); 87 if (error) { 88 uvm_uarea_system_free(uaddr); 89 return error; 90 } 91 if (fmt != NULL) { 92 l->l_name = kmem_alloc(MAXCOMLEN, KM_SLEEP); 93 va_start(ap, fmt); 94 vsnprintf(l->l_name, MAXCOMLEN, fmt, ap); 95 va_end(ap); 96 } 97 98 /* 99 * Set parameters. 100 */ 101 if (pri == PRI_NONE) { 102 if ((flag & KTHREAD_TS) != 0) { 103 /* Maximum user priority level. */ 104 pri = MAXPRI_USER; 105 } else { 106 /* Minimum kernel priority level. */ 107 pri = PRI_KTHREAD; 108 } 109 } 110 mutex_enter(proc0.p_lock); 111 lwp_lock(l); 112 lwp_changepri(l, pri); 113 if (ci != NULL) { 114 if (ci != l->l_cpu) { 115 lwp_unlock_to(l, ci->ci_schedstate.spc_lwplock); 116 lwp_lock(l); 117 } 118 l->l_pflag |= LP_BOUND; 119 l->l_cpu = ci; 120 } 121 122 if ((flag & KTHREAD_MUSTJOIN) != 0) { 123 KASSERT(lp != NULL); 124 l->l_pflag |= LP_MUSTJOIN; 125 } 126 if ((flag & KTHREAD_INTR) != 0) { 127 l->l_pflag |= LP_INTR; 128 } 129 if ((flag & KTHREAD_MPSAFE) == 0) { 130 l->l_pflag &= ~LP_MPSAFE; 131 } 132 133 /* 134 * Set the new LWP running, unless the caller has requested 135 * otherwise. 136 */ 137 KASSERT(l->l_stat == LSIDL); 138 if ((flag & KTHREAD_IDLE) == 0) { 139 setrunnable(l); 140 /* LWP now unlocked */ 141 } else { 142 lwp_unlock(l); 143 } 144 mutex_exit(proc0.p_lock); 145 146 /* All done! */ 147 if (lp != NULL) { 148 *lp = l; 149 } 150 return 0; 151} 152 153/* 154 * Cause a kernel thread to exit. Assumes the exiting thread is the 155 * current context. 156 */ 157void 158kthread_exit(int ecode) 159{ 160 const char *name; 161 lwp_t *l = curlwp; 162 163 /* We can't do much with the exit code, so just report it. */ 164 if (ecode != 0) { 165 if ((name = l->l_name) == NULL) 166 name = "unnamed"; 167 printf("WARNING: kthread `%s' (%d) exits with status %d\n", 168 name, l->l_lid, ecode); 169 } 170 171 /* Barrier for joining. */ 172 if (l->l_pflag & LP_MUSTJOIN) { 173 bool *exitedp; 174 175 mutex_enter(&kthread_lock); 176 while ((exitedp = l->l_private) == NULL) { 177 cv_wait(&kthread_cv, &kthread_lock); 178 } 179 KASSERT(!*exitedp); 180 *exitedp = true; 181 cv_broadcast(&kthread_cv); 182 mutex_exit(&kthread_lock); 183 } 184 185 /* If the kernel lock is held, we need to drop it now. */ 186 if ((l->l_pflag & LP_MPSAFE) == 0) { 187 KERNEL_UNLOCK_LAST(l); 188 } 189 190 /* And exit.. */ 191 lwp_exit(l); 192 panic("kthread_exit"); 193} 194 195/* 196 * Wait for a kthread to exit, as pthread_join(). 197 */ 198int 199kthread_join(lwp_t *l) 200{ 201 bool exited = false; 202 203 KASSERT((l->l_flag & LW_SYSTEM) != 0); 204 KASSERT((l->l_pflag & LP_MUSTJOIN) != 0); 205 206 /* 207 * - Ask the kthread to write to `exited'. 208 * - After this, touching l is forbidden -- it may be freed. 209 * - Wait until the kthread has written to `exited'. 210 */ 211 mutex_enter(&kthread_lock); 212 KASSERT(l->l_private == NULL); 213 l->l_private = &exited; 214 cv_broadcast(&kthread_cv); 215 while (!exited) { 216 cv_wait(&kthread_cv, &kthread_lock); 217 } 218 mutex_exit(&kthread_lock); 219 220 return 0; 221} 222 223/* 224 * kthread_fpu_enter() 225 * 226 * Allow the current lwp, which must be a kthread, to use the FPU. 227 * Return a cookie that must be passed to kthread_fpu_exit when 228 * done. Must be used only in thread context. Recursive -- you 229 * can call kthread_fpu_enter several times in a row as long as 230 * you pass the cookies in reverse order to kthread_fpu_exit. 231 */ 232int 233kthread_fpu_enter(void) 234{ 235 struct lwp *l = curlwp; 236 int s; 237 238 KASSERTMSG(!cpu_intr_p(), 239 "%s is not allowed in interrupt context", __func__); 240 KASSERTMSG(!cpu_softintr_p(), 241 "%s is not allowed in interrupt context", __func__); 242 243 /* 244 * Remember whether this thread already had FPU access, and 245 * mark this thread as having FPU access. 246 */ 247 lwp_lock(l); 248 KASSERTMSG(l->l_flag & LW_SYSTEM, 249 "%s is allowed only in kthreads", __func__); 250 s = l->l_flag & LW_SYSTEM_FPU; 251 l->l_flag |= LW_SYSTEM_FPU; 252 lwp_unlock(l); 253 254 /* Take MD steps to enable the FPU if necessary. */ 255 if (s == 0) 256 kthread_fpu_enter_md(); 257 258 return s; 259} 260 261/* 262 * kthread_fpu_exit(s) 263 * 264 * Restore the current lwp's FPU access to what it was before the 265 * matching call to kthread_fpu_enter() that returned s. Must be 266 * used only in thread context. 267 */ 268void 269kthread_fpu_exit(int s) 270{ 271 struct lwp *l = curlwp; 272 273 KASSERT(s == (s & LW_SYSTEM_FPU)); 274 KASSERTMSG(!cpu_intr_p(), 275 "%s is not allowed in interrupt context", __func__); 276 KASSERTMSG(!cpu_softintr_p(), 277 "%s is not allowed in interrupt context", __func__); 278 279 lwp_lock(l); 280 KASSERTMSG(l->l_flag & LW_SYSTEM, 281 "%s is allowed only in kthreads", __func__); 282 KASSERT(l->l_flag & LW_SYSTEM_FPU); 283 l->l_flag ^= s ^ LW_SYSTEM_FPU; 284 lwp_unlock(l); 285 286 /* Take MD steps to zero and disable the FPU if necessary. */ 287 if (s == 0) 288 kthread_fpu_exit_md(); 289} 290