1 /* $NetBSD: kern_kthread.c,v 1.46 2020/08/01 02:04:55 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 1.46 2020/08/01 02:04:55 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 45 #include <uvm/uvm_extern.h> 46 47 static lwp_t * kthread_jtarget; 48 static kmutex_t kthread_lock; 49 static kcondvar_t kthread_cv; 50 51 void 52 kthread_sysinit(void) 53 { 54 55 mutex_init(&kthread_lock, MUTEX_DEFAULT, IPL_NONE); 56 cv_init(&kthread_cv, "kthrwait"); 57 kthread_jtarget = NULL; 58 } 59 60 /* 61 * kthread_create: create a kernel thread, that is, system-only LWP. 62 */ 63 int 64 kthread_create(pri_t pri, int flag, struct cpu_info *ci, 65 void (*func)(void *), void *arg, lwp_t **lp, const char *fmt, ...) 66 { 67 lwp_t *l; 68 vaddr_t uaddr; 69 int error, lc; 70 va_list ap; 71 72 KASSERT((flag & KTHREAD_INTR) == 0 || (flag & KTHREAD_MPSAFE) != 0); 73 74 uaddr = uvm_uarea_system_alloc( 75 (flag & (KTHREAD_INTR|KTHREAD_IDLE)) == KTHREAD_IDLE ? ci : NULL); 76 if (uaddr == 0) { 77 return ENOMEM; 78 } 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 */ 157 void 158 kthread_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 mutex_enter(&kthread_lock); 174 while (kthread_jtarget != l) { 175 cv_wait(&kthread_cv, &kthread_lock); 176 } 177 kthread_jtarget = NULL; 178 cv_broadcast(&kthread_cv); 179 mutex_exit(&kthread_lock); 180 } 181 182 /* If the kernel lock is held, we need to drop it now. */ 183 if ((l->l_pflag & LP_MPSAFE) == 0) { 184 KERNEL_UNLOCK_LAST(l); 185 } 186 187 /* And exit.. */ 188 lwp_exit(l); 189 panic("kthread_exit"); 190 } 191 192 /* 193 * Wait for a kthread to exit, as pthread_join(). 194 */ 195 int 196 kthread_join(lwp_t *l) 197 { 198 199 KASSERT((l->l_flag & LW_SYSTEM) != 0); 200 KASSERT((l->l_pflag & LP_MUSTJOIN) != 0); 201 202 /* 203 * - Wait if some other thread has occupied the target. 204 * - Specify our kthread as a target and notify it. 205 * - Wait for the target kthread to notify us. 206 */ 207 mutex_enter(&kthread_lock); 208 while (kthread_jtarget) { 209 cv_wait(&kthread_cv, &kthread_lock); 210 } 211 kthread_jtarget = l; 212 cv_broadcast(&kthread_cv); 213 while (kthread_jtarget == l) { 214 cv_wait(&kthread_cv, &kthread_lock); 215 } 216 mutex_exit(&kthread_lock); 217 218 return 0; 219 } 220 221 /* 222 * kthread_fpu_enter() 223 * 224 * Allow the current lwp, which must be a kthread, to use the FPU. 225 * Return a cookie that must be passed to kthread_fpu_exit when 226 * done. Must be used only in thread context. Recursive -- you 227 * can call kthread_fpu_enter several times in a row as long as 228 * you pass the cookies in reverse order to kthread_fpu_exit. 229 */ 230 int 231 kthread_fpu_enter(void) 232 { 233 struct lwp *l = curlwp; 234 int s; 235 236 KASSERTMSG(!cpu_intr_p(), 237 "%s is not allowed in interrupt context", __func__); 238 KASSERTMSG(!cpu_softintr_p(), 239 "%s is not allowed in interrupt context", __func__); 240 241 /* 242 * Remember whether this thread already had FPU access, and 243 * mark this thread as having FPU access. 244 */ 245 lwp_lock(l); 246 KASSERTMSG(l->l_flag & LW_SYSTEM, 247 "%s is allowed only in kthreads", __func__); 248 s = l->l_flag & LW_SYSTEM_FPU; 249 l->l_flag |= LW_SYSTEM_FPU; 250 lwp_unlock(l); 251 252 /* Take MD steps to enable the FPU if necessary. */ 253 if (s == 0) 254 kthread_fpu_enter_md(); 255 256 return s; 257 } 258 259 /* 260 * kthread_fpu_exit(s) 261 * 262 * Restore the current lwp's FPU access to what it was before the 263 * matching call to kthread_fpu_enter() that returned s. Must be 264 * used only in thread context. 265 */ 266 void 267 kthread_fpu_exit(int s) 268 { 269 struct lwp *l = curlwp; 270 271 KASSERT(s == (s & LW_SYSTEM_FPU)); 272 KASSERTMSG(!cpu_intr_p(), 273 "%s is not allowed in interrupt context", __func__); 274 KASSERTMSG(!cpu_softintr_p(), 275 "%s is not allowed in interrupt context", __func__); 276 277 lwp_lock(l); 278 KASSERTMSG(l->l_flag & LW_SYSTEM, 279 "%s is allowed only in kthreads", __func__); 280 KASSERT(l->l_flag & LW_SYSTEM_FPU); 281 l->l_flag ^= s ^ LW_SYSTEM_FPU; 282 lwp_unlock(l); 283 284 /* Take MD steps to zero and disable the FPU if necessary. */ 285 if (s == 0) 286 kthread_fpu_exit_md(); 287 } 288