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 thread_t td; 123 124 if (uap->timeout < 0) 125 return (EINVAL); 126 td = curthread; 127 128 if (td->td_vmm) { 129 register_t gpa; 130 vmm_vm_get_gpa(td->td_proc, &gpa, (register_t)uap->ptr); 131 uap->ptr = (const int *)gpa; 132 } 133 134 uptr = __DEQUALIFY(void *, uap->ptr); 135 if ((vm_offset_t)uptr & (sizeof(int) - 1)) 136 return EFAULT; 137 138 offset = (vm_offset_t)uptr & PAGE_MASK; 139 140 /* 141 * Resolve the physical address. We allow the case where there are 142 * sometimes discontinuities (causing a 2 second retry timeout). 143 */ 144 retry_on_discontinuity: 145 fail_counter = 10000; 146 do { 147 if (--fail_counter == 0) { 148 kprintf("umtx_sleep() (X): ERROR Discontinuity %p (%s %d/%d)\n", 149 uptr, td->td_comm, 150 (int)td->td_proc->p_pid, 151 (int)td->td_lwp->lwp_tid); 152 return EINVAL; 153 } 154 value = fuwordadd32(uptr, 0); 155 waddr = (void *)(intptr_t)uservtophys((intptr_t)uptr); 156 } while (waddr == (void *)(intptr_t)-1 && value != -1); 157 158 if (value == -1 && waddr == (void *)(intptr_t)-1) { 159 kprintf("umtx_sleep() (A): WARNING can't translate %p (%s %d/%d)\n", 160 uptr, td->td_comm, 161 (int)td->td_proc->p_pid, 162 (int)td->td_lwp->lwp_tid); 163 return EINVAL; 164 } 165 166 error = EBUSY; 167 if (value == uap->value) { 168 #ifdef _RDTSC_SUPPORTED_ 169 /* 170 * Poll a little while before sleeping, most mutexes are 171 * short-lived. 172 */ 173 if (umtx_delay) { 174 int64_t tsc_target; 175 int good = 0; 176 177 tsc_target = tsc_get_target(umtx_delay); 178 while (tsc_test_target(tsc_target) == 0) { 179 cpu_lfence(); 180 if (fuwordadd32(uptr, 0) != uap->value) { 181 good = 1; 182 break; 183 } 184 cpu_pause(); 185 } 186 if (good) { 187 error = EBUSY; 188 goto done; 189 } 190 } 191 #endif 192 /* 193 * Calculate the timeout. This will be acccurate to within ~2 ticks. 194 * uap->timeout is in microseconds. 195 */ 196 timeout = umtx_timeout_max; 197 if (uap->timeout && uap->timeout < timeout) 198 timeout = uap->timeout; 199 timeout = (timeout / 1000000) * hz + 200 ((timeout % 1000000) * hz + 999999) / 1000000; 201 202 /* 203 * Wake us up if the memory location COWs while we are sleeping. 204 * Use a critical section to tighten up the interlock. Also, 205 * tsleep_remove() requires the caller be in a critical section. 206 */ 207 crit_enter(); 208 209 /* 210 * We must interlock just before sleeping. If we interlock before 211 * registration the lock operations done by the registration can 212 * interfere with it. 213 * 214 * We cannot leave our interlock hanging on return because this 215 * will interfere with umtx_wakeup() calls with limited wakeup 216 * counts. 217 */ 218 tsleep_interlock(waddr, PCATCH | PDOMAIN_UMTX); 219 220 /* 221 * Check physical address changed 222 */ 223 cpu_lfence(); 224 if ((void *)(intptr_t)uservtophys((intptr_t)uptr) != waddr) { 225 crit_exit(); 226 goto retry_on_discontinuity; 227 } 228 229 /* 230 * Re-read value 231 */ 232 value = fuwordadd32(uptr, 0); 233 234 if (value == uap->value) { 235 error = tsleep(waddr, PCATCH | PINTERLOCKED | PDOMAIN_UMTX, 236 "umtxsl", timeout); 237 } else { 238 error = EBUSY; 239 } 240 crit_exit(); 241 /* Always break out in case of signal, even if restartable */ 242 if (error == ERESTART) 243 error = EINTR; 244 } else { 245 error = EBUSY; 246 } 247 done: 248 return(error); 249 } 250 251 /* 252 * umtx_wakeup { const int *ptr, int count } 253 * 254 * Wakeup the specified number of processes held in umtx_sleep() on the 255 * specified user address. A count of 0 wakes up all waiting processes. 256 */ 257 int 258 sys_umtx_wakeup(struct umtx_wakeup_args *uap) 259 { 260 int offset; 261 int error; 262 int fail_counter; 263 int32_t value; 264 void *waddr; 265 void *uptr; 266 thread_t td; 267 268 td = curthread; 269 270 if (td->td_vmm) { 271 register_t gpa; 272 vmm_vm_get_gpa(td->td_proc, &gpa, (register_t)uap->ptr); 273 uap->ptr = (const int *)gpa; 274 } 275 276 /* 277 * WARNING! We can only use vm_fault_page*() for reading data. We 278 * cannot use it for writing data because there is no pmap 279 * interlock to protect against flushes/pageouts. 280 */ 281 cpu_mfence(); 282 if ((vm_offset_t)uap->ptr & (sizeof(int) - 1)) 283 return EFAULT; 284 285 offset = (vm_offset_t)uap->ptr & PAGE_MASK; 286 uptr = __DEQUALIFY(void *, uap->ptr); 287 288 fail_counter = 10000; 289 do { 290 if (--fail_counter == 0) { 291 kprintf("umtx_wakeup() (X): ERROR Discontinuity " 292 "%p (%s %d/%d)\n", 293 uptr, td->td_comm, 294 (int)td->td_proc->p_pid, 295 (int)td->td_lwp->lwp_tid); 296 return EINVAL; 297 } 298 value = fuwordadd32(uptr, 0); 299 waddr = (void *)(intptr_t)uservtophys((intptr_t)uptr); 300 } while (waddr == (void *)(intptr_t)-1 && value != -1); 301 302 if (value == -1 && waddr == (void *)(intptr_t)-1) { 303 kprintf("umtx_wakeup() (A): WARNING can't translate %p (%s %d/%d)\n", 304 uptr, td->td_comm, 305 (int)td->td_proc->p_pid, 306 (int)td->td_lwp->lwp_tid); 307 return EINVAL; 308 } 309 310 if (uap->count == 1) { 311 wakeup_domain_one(waddr, PDOMAIN_UMTX); 312 } else { 313 /* XXX wakes them all up for now */ 314 wakeup_domain(waddr, PDOMAIN_UMTX); 315 } 316 error = 0; 317 318 return(error); 319 } 320