1 /* 2 * Copyright (c) 2003,2004,2010,2017 The DragonFly Project. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Matthew Dillon <dillon@backplane.com> and David Xu <davidxu@freebsd.org> 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in 16 * the documentation and/or other materials provided with the 17 * distribution. 18 * 3. Neither the name of The DragonFly Project nor the names of its 19 * contributors may be used to endorse or promote products derived 20 * from this software without specific, prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 23 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 24 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 25 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 26 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 27 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 28 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 29 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 30 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 31 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 32 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 /* 37 * This module implements userland mutex helper functions. umtx_sleep() 38 * handling blocking and umtx_wakeup() handles wakeups. The sleep/wakeup 39 * functions operate on user addresses. 40 */ 41 42 #include <sys/param.h> 43 #include <sys/systm.h> 44 #include <sys/cdefs.h> 45 #include <sys/kernel.h> 46 #include <sys/sysproto.h> 47 #include <sys/sysunion.h> 48 #include <sys/sysent.h> 49 #include <sys/syscall.h> 50 #include <sys/sysctl.h> 51 #include <sys/module.h> 52 #include <sys/thread.h> 53 #include <sys/proc.h> 54 55 #include <cpu/lwbuf.h> 56 57 #include <vm/vm.h> 58 #include <vm/vm_param.h> 59 #include <sys/lock.h> 60 #include <vm/pmap.h> 61 #include <vm/vm_map.h> 62 #include <vm/vm_object.h> 63 #include <vm/vm_page.h> 64 #include <vm/vm_pager.h> 65 #include <vm/vm_pageout.h> 66 #include <vm/vm_extern.h> 67 #include <vm/vm_kern.h> 68 69 #include <vm/vm_page2.h> 70 71 #include <machine/vmm.h> 72 73 /* 74 * Improve umtx performance by polling for 4000nS before going to sleep. 75 * This can avoid many IPIs in typical pthreads mutex situations. 76 */ 77 #ifdef _RDTSC_SUPPORTED_ 78 static int umtx_delay = 4000; /* nS */ 79 SYSCTL_INT(_kern, OID_AUTO, umtx_delay, CTLFLAG_RW, 80 &umtx_delay, 0, ""); 81 #endif 82 static int umtx_timeout_max = 2000000; /* microseconds */ 83 SYSCTL_INT(_kern, OID_AUTO, umtx_timeout_max, CTLFLAG_RW, 84 &umtx_timeout_max, 0, ""); 85 86 /* 87 * If the contents of the userland-supplied pointer matches the specified 88 * value enter an interruptable sleep for up to <timeout> microseconds. 89 * If the contents does not match then return immediately. 90 * 91 * Returns 0 if we slept and were woken up, -1 and EWOULDBLOCK if we slept 92 * and timed out, and EBUSY if the contents of the pointer already does 93 * not match the specified value. A timeout of 0 indicates an unlimited sleep. 94 * EINTR is returned if the call was interrupted by a signal (even if 95 * the signal specifies that the system call should restart). 96 * 97 * This function interlocks against call to umtx_wakeup. It does NOT interlock 98 * against changes in *ptr. However, it does not have to. The standard use 99 * of *ptr is to differentiate between an uncontested and a contested mutex 100 * and call umtx_wakeup when releasing a contested mutex. Therefore we can 101 * safely race against changes in *ptr as long as we are properly interlocked 102 * against the umtx_wakeup() call. 103 * 104 * For performance reasons, we do not try to track the underlying page for 105 * mapping changes. Instead, the timeout is capped at kern.umtx_timeout_max 106 * (default 1 second) and the caller is expected to retry. The kernel 107 * will wake all umtx_sleep()s if the process fork()s, but not if it vfork()s. 108 * Other mapping changes must be caught by the timeout. 109 * 110 * umtx_sleep { const int *ptr, int value, int timeout } 111 */ 112 int 113 sys_umtx_sleep(struct umtx_sleep_args *uap) 114 { 115 void *waddr; 116 void *uptr; 117 int offset; 118 int timeout; 119 int error; 120 int value; 121 int fail_counter; 122 123 if (uap->timeout < 0) 124 return (EINVAL); 125 126 if (curthread->td_vmm) { 127 register_t gpa; 128 vmm_vm_get_gpa(curproc, &gpa, (register_t)uap->ptr); 129 uap->ptr = (const int *)gpa; 130 } 131 132 uptr = __DEQUALIFY(void *, uap->ptr); 133 if ((vm_offset_t)uptr & (sizeof(int) - 1)) 134 return EFAULT; 135 136 offset = (vm_offset_t)uptr & PAGE_MASK; 137 138 /* 139 * Resolve the physical address. We allow the case where there are 140 * sometimes discontinuities (causing a 2 second retry timeout). 141 */ 142 retry_on_discontinuity: 143 fail_counter = 10000; 144 do { 145 if (--fail_counter == 0) { 146 kprintf("umtx_sleep() (X): ERROR Discontinuity %p (%s %d/%d)\n", 147 uptr, curthread->td_comm, 148 (int)curthread->td_proc->p_pid, 149 (int)curthread->td_lwp->lwp_tid); 150 return EINVAL; 151 } 152 value = fuword32(uptr); 153 waddr = (void *)(intptr_t)uservtophys((intptr_t)uptr); 154 } while (waddr == (void *)(intptr_t)-1 && value != -1); 155 156 if (value == -1 && waddr == (void *)(intptr_t)-1) { 157 kprintf("umtx_sleep() (A): WARNING can't translate %p (%s %d/%d)\n", 158 uptr, curthread->td_comm, 159 (int)curthread->td_proc->p_pid, 160 (int)curthread->td_lwp->lwp_tid); 161 return EINVAL; 162 } 163 164 error = EBUSY; 165 if (value == uap->value) { 166 #ifdef _RDTSC_SUPPORTED_ 167 /* 168 * Poll a little while before sleeping, most mutexes are 169 * short-lived. 170 */ 171 if (umtx_delay) { 172 int64_t tsc_target; 173 int good = 0; 174 175 tsc_target = tsc_get_target(umtx_delay); 176 while (tsc_test_target(tsc_target) == 0) { 177 cpu_lfence(); 178 if (fuword32(uptr) != uap->value) { 179 good = 1; 180 break; 181 } 182 cpu_pause(); 183 } 184 if (good) { 185 error = EBUSY; 186 goto done; 187 } 188 } 189 #endif 190 /* 191 * Calculate the timeout. This will be acccurate to within ~2 ticks. 192 * uap->timeout is in microseconds. 193 */ 194 timeout = umtx_timeout_max; 195 if (uap->timeout && uap->timeout < timeout) 196 timeout = uap->timeout; 197 timeout = (timeout / 1000000) * hz + 198 ((timeout % 1000000) * hz + 999999) / 1000000; 199 200 /* 201 * Wake us up if the memory location COWs while we are sleeping. 202 * Use a critical section to tighten up the interlock. Also, 203 * tsleep_remove() requires the caller be in a critical section. 204 */ 205 crit_enter(); 206 207 /* 208 * We must interlock just before sleeping. If we interlock before 209 * registration the lock operations done by the registration can 210 * interfere with it. 211 * 212 * We cannot leave our interlock hanging on return because this 213 * will interfere with umtx_wakeup() calls with limited wakeup 214 * counts. 215 */ 216 tsleep_interlock(waddr, PCATCH | PDOMAIN_UMTX); 217 cpu_lfence(); 218 if ((void *)(intptr_t)uservtophys((intptr_t)uptr) != waddr) { 219 crit_exit(); 220 goto retry_on_discontinuity; 221 } 222 value = fuword32(uptr); 223 if (value == uap->value) { 224 error = tsleep(waddr, PCATCH | PINTERLOCKED | PDOMAIN_UMTX, 225 "umtxsl", timeout); 226 } else { 227 error = EBUSY; 228 } 229 crit_exit(); 230 /* Always break out in case of signal, even if restartable */ 231 if (error == ERESTART) 232 error = EINTR; 233 } else { 234 error = EBUSY; 235 } 236 done: 237 return(error); 238 } 239 240 /* 241 * umtx_wakeup { const int *ptr, int count } 242 * 243 * Wakeup the specified number of processes held in umtx_sleep() on the 244 * specified user address. A count of 0 wakes up all waiting processes. 245 */ 246 int 247 sys_umtx_wakeup(struct umtx_wakeup_args *uap) 248 { 249 int offset; 250 int error; 251 int fail_counter; 252 int32_t value; 253 void *waddr; 254 void *uptr; 255 256 if (curthread->td_vmm) { 257 register_t gpa; 258 vmm_vm_get_gpa(curproc, &gpa, (register_t)uap->ptr); 259 uap->ptr = (const int *)gpa; 260 } 261 262 /* 263 * WARNING! We can only use vm_fault_page*() for reading data. We 264 * cannot use it for writing data because there is no pmap 265 * interlock to protect against flushes/pageouts. 266 */ 267 cpu_mfence(); 268 if ((vm_offset_t)uap->ptr & (sizeof(int) - 1)) 269 return EFAULT; 270 271 offset = (vm_offset_t)uap->ptr & PAGE_MASK; 272 uptr = __DEQUALIFY(void *, uap->ptr); 273 274 fail_counter = 10000; 275 do { 276 if (--fail_counter == 0) { 277 kprintf("umtx_wakeup() (X): ERROR Discontinuity " 278 "%p (%s %d/%d)\n", 279 uptr, curthread->td_comm, 280 (int)curthread->td_proc->p_pid, 281 (int)curthread->td_lwp->lwp_tid); 282 return EINVAL; 283 } 284 value = fuword32(uptr); 285 waddr = (void *)(intptr_t)uservtophys((intptr_t)uptr); 286 } while (waddr == (void *)(intptr_t)-1 && value != -1); 287 288 if (value == -1 && waddr == (void *)(intptr_t)-1) { 289 kprintf("umtx_wakeup() (A): WARNING can't translate %p (%s %d/%d)\n", 290 uptr, curthread->td_comm, 291 (int)curthread->td_proc->p_pid, 292 (int)curthread->td_lwp->lwp_tid); 293 return EINVAL; 294 } 295 296 if (uap->count == 1) { 297 wakeup_domain_one(waddr, PDOMAIN_UMTX); 298 } else { 299 /* XXX wakes them all up for now */ 300 wakeup_domain(waddr, PDOMAIN_UMTX); 301 } 302 error = 0; 303 304 return(error); 305 } 306