1 /* 2 * (MPSAFE) 3 * 4 * Copyright (c) 2003,2004,2010 The DragonFly Project. All rights reserved. 5 * 6 * This code is derived from software contributed to The DragonFly Project 7 * by Matthew Dillon <dillon@backplane.com> and David Xu <davidxu@freebsd.org> 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in 17 * the documentation and/or other materials provided with the 18 * distribution. 19 * 3. Neither the name of The DragonFly Project nor the names of its 20 * contributors may be used to endorse or promote products derived 21 * from this software without specific, prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 24 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 25 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 26 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 27 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 28 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 29 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 30 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 31 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 32 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 33 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 /* 38 * This module implements userland mutex helper functions. umtx_sleep() 39 * handling blocking and umtx_wakeup() handles wakeups. The sleep/wakeup 40 * functions operate on user addresses. 41 */ 42 43 #include <sys/param.h> 44 #include <sys/systm.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/module.h> 51 52 #include <cpu/lwbuf.h> 53 54 #include <vm/vm.h> 55 #include <vm/vm_param.h> 56 #include <sys/lock.h> 57 #include <vm/pmap.h> 58 #include <vm/vm_map.h> 59 #include <vm/vm_object.h> 60 #include <vm/vm_page.h> 61 #include <vm/vm_pager.h> 62 #include <vm/vm_pageout.h> 63 #include <vm/vm_extern.h> 64 #include <vm/vm_kern.h> 65 66 #include <vm/vm_page2.h> 67 68 #include <machine/vmm.h> 69 70 static void umtx_sleep_page_action_cow(vm_page_t m, vm_page_action_t action); 71 72 /* 73 * If the contents of the userland-supplied pointer matches the specified 74 * value enter an interruptable sleep for up to <timeout> microseconds. 75 * If the contents does not match then return immediately. 76 * 77 * Returns 0 if we slept and were woken up, -1 and EWOULDBLOCK if we slept 78 * and timed out, and EBUSY if the contents of the pointer already does 79 * not match the specified value. A timeout of 0 indicates an unlimited sleep. 80 * EINTR is returned if the call was interrupted by a signal (even if 81 * the signal specifies that the system call should restart). 82 * 83 * This function interlocks against call to umtx_wakeup. It does NOT interlock 84 * against changes in *ptr. However, it does not have to. The standard use 85 * of *ptr is to differentiate between an uncontested and a contested mutex 86 * and call umtx_wakeup when releasing a contested mutex. Therefore we can 87 * safely race against changes in *ptr as long as we are properly interlocked 88 * against the umtx_wakeup() call. 89 * 90 * The VM page associated with the mutex is held in an attempt to keep 91 * the mutex's physical address consistent, allowing umtx_sleep() and 92 * umtx_wakeup() to use the physical address as their rendezvous. BUT 93 * situations can arise where the physical address may change, particularly 94 * if a threaded program fork()'s and the mutex's memory becomes 95 * copy-on-write. We register an event on the VM page to catch COWs. 96 * 97 * umtx_sleep { const int *ptr, int value, int timeout } 98 */ 99 int 100 sys_umtx_sleep(struct umtx_sleep_args *uap) 101 { 102 struct lwbuf lwb_cache; 103 struct lwbuf *lwb; 104 struct vm_page_action action; 105 vm_page_t m; 106 void *waddr; 107 int offset; 108 int timeout; 109 int error = EBUSY; 110 111 if (uap->timeout < 0) 112 return (EINVAL); 113 114 if (curthread->td_vmm) { 115 register_t gpa; 116 vmm_vm_get_gpa(curproc, &gpa, (register_t) uap->ptr); 117 uap->ptr = (const int *)gpa; 118 } 119 120 if ((vm_offset_t)uap->ptr & (sizeof(int) - 1)) 121 return (EFAULT); 122 123 /* 124 * When faulting in the page, force any COW pages to be resolved. 125 * Otherwise the physical page we sleep on my not match the page 126 * being woken up. 127 */ 128 m = vm_fault_page_quick((vm_offset_t)uap->ptr, 129 VM_PROT_READ|VM_PROT_WRITE, &error); 130 if (m == NULL) { 131 error = EFAULT; 132 goto done; 133 } 134 lwb = lwbuf_alloc(m, &lwb_cache); 135 offset = (vm_offset_t)uap->ptr & PAGE_MASK; 136 137 /* 138 * The critical section is required to interlock the tsleep against 139 * a wakeup from another cpu. The lfence forces synchronization. 140 */ 141 if (*(int *)(lwbuf_kva(lwb) + offset) == uap->value) { 142 if ((timeout = uap->timeout) != 0) { 143 timeout = (timeout / 1000000) * hz + 144 ((timeout % 1000000) * hz + 999999) / 1000000; 145 } 146 waddr = (void *)((intptr_t)VM_PAGE_TO_PHYS(m) + offset); 147 148 /* 149 * Wake us up if the memory location COWs while we are sleeping. 150 */ 151 crit_enter(); 152 vm_page_init_action(m, &action, umtx_sleep_page_action_cow, waddr); 153 vm_page_register_action(&action, VMEVENT_COW); 154 155 /* 156 * We must interlock just before sleeping. If we interlock before 157 * registration the lock operations done by the registration can 158 * interfere with it. 159 */ 160 tsleep_interlock(waddr, PCATCH | PDOMAIN_UMTX); 161 if (*(int *)(lwbuf_kva(lwb) + offset) == uap->value && 162 action.event == VMEVENT_COW) { 163 error = tsleep(waddr, PCATCH | PINTERLOCKED | PDOMAIN_UMTX, 164 "umtxsl", timeout); 165 } else { 166 error = EBUSY; 167 } 168 vm_page_unregister_action(&action); 169 crit_exit(); 170 /* Always break out in case of signal, even if restartable */ 171 if (error == ERESTART) 172 error = EINTR; 173 } else { 174 error = EBUSY; 175 } 176 177 lwbuf_free(lwb); 178 /*vm_page_dirty(m); we don't actually dirty the page */ 179 vm_page_unhold(m); 180 done: 181 return(error); 182 } 183 184 /* 185 * If this page is being copied it may no longer represent the page 186 * underlying our virtual address. Wake up any umtx_sleep()'s 187 * that were waiting on its physical address to force them to retry. 188 */ 189 static void 190 umtx_sleep_page_action_cow(vm_page_t m, vm_page_action_t action) 191 { 192 wakeup_domain(action->data, PDOMAIN_UMTX); 193 } 194 195 /* 196 * umtx_wakeup { const int *ptr, int count } 197 * 198 * Wakeup the specified number of processes held in umtx_sleep() on the 199 * specified user address. A count of 0 wakes up all waiting processes. 200 * 201 * XXX assumes that the physical address space does not exceed the virtual 202 * address space. 203 */ 204 int 205 sys_umtx_wakeup(struct umtx_wakeup_args *uap) 206 { 207 vm_page_t m; 208 int offset; 209 int error; 210 void *waddr; 211 212 if (curthread->td_vmm) { 213 register_t gpa; 214 vmm_vm_get_gpa(curproc, &gpa, (register_t) uap->ptr); 215 uap->ptr = (const int *)gpa; 216 } 217 218 cpu_mfence(); 219 if ((vm_offset_t)uap->ptr & (sizeof(int) - 1)) 220 return (EFAULT); 221 m = vm_fault_page_quick((vm_offset_t)uap->ptr, VM_PROT_READ, &error); 222 if (m == NULL) { 223 error = EFAULT; 224 goto done; 225 } 226 offset = (vm_offset_t)uap->ptr & PAGE_MASK; 227 waddr = (void *)((intptr_t)VM_PAGE_TO_PHYS(m) + offset); 228 229 if (uap->count == 1) { 230 wakeup_domain_one(waddr, PDOMAIN_UMTX); 231 } else { 232 /* XXX wakes them all up for now */ 233 wakeup_domain(waddr, PDOMAIN_UMTX); 234 } 235 vm_page_unhold(m); 236 error = 0; 237 done: 238 return(error); 239 } 240 241