| 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 | * $DragonFly: src/sys/kern/kern_umtx.c,v 1.9 2008/05/09 07:24:45 dillon Exp $ |
| 37 | */ |
| 38 | |
| 39 | /* |
| 40 | * This module implements userland mutex helper functions. umtx_sleep() |
| 41 | * handling blocking and umtx_wakeup() handles wakeups. The sleep/wakeup |
| 42 | * functions operate on user addresses. |
| 43 | */ |
| 44 | |
| 45 | #include <sys/param.h> |
| 46 | #include <sys/systm.h> |
| 47 | #include <sys/kernel.h> |
| 48 | #include <sys/sysproto.h> |
| 49 | #include <sys/sysunion.h> |
| 50 | #include <sys/sysent.h> |
| 51 | #include <sys/syscall.h> |
| 52 | #include <sys/module.h> |
| 53 | |
| 54 | #include <cpu/lwbuf.h> |
| 55 | |
| 56 | #include <vm/vm.h> |
| 57 | #include <vm/vm_param.h> |
| 58 | #include <sys/lock.h> |
| 59 | #include <vm/pmap.h> |
| 60 | #include <vm/vm_map.h> |
| 61 | #include <vm/vm_object.h> |
| 62 | #include <vm/vm_page.h> |
| 63 | #include <vm/vm_pager.h> |
| 64 | #include <vm/vm_pageout.h> |
| 65 | #include <vm/vm_extern.h> |
| 66 | #include <vm/vm_page.h> |
| 67 | #include <vm/vm_kern.h> |
| 68 | |
| 69 | #include <vm/vm_page2.h> |
| 70 | |
| 71 | static void umtx_sleep_page_action_cow(vm_page_t m, vm_page_action_t action); |
| 72 | |
| 73 | /* |
| 74 | * If the contents of the userland-supplied pointer matches the specified |
| 75 | * value enter an interruptable sleep for up to <timeout> microseconds. |
| 76 | * If the contents does not match then return immediately. |
| 77 | * |
| 78 | * Returns 0 if we slept and were woken up, -1 and EWOULDBLOCK if we slept |
| 79 | * and timed out, and EBUSY if the contents of the pointer already does |
| 80 | * not match the specified value. A timeout of 0 indicates an unlimited sleep. |
| 81 | * EINTR is returned if the call was interrupted by a signal (even if |
| 82 | * the signal specifies that the system call should restart). |
| 83 | * |
| 84 | * This function interlocks against call to umtx_wakeup. It does NOT interlock |
| 85 | * against changes in *ptr. However, it does not have to. The standard use |
| 86 | * of *ptr is to differentiate between an uncontested and a contested mutex |
| 87 | * and call umtx_wakeup when releasing a contested mutex. Therefore we can |
| 88 | * safely race against changes in *ptr as long as we are properly interlocked |
| 89 | * against the umtx_wakeup() call. |
| 90 | * |
| 91 | * The VM page associated with the mutex is held in an attempt to keep |
| 92 | * the mutex's physical address consistent, allowing umtx_sleep() and |
| 93 | * umtx_wakeup() to use the physical address as their rendezvous. BUT |
| 94 | * situations can arise where the physical address may change, particularly |
| 95 | * if a threaded program fork()'s and the mutex's memory becomes |
| 96 | * copy-on-write. We register an event on the VM page to catch COWs. |
| 97 | * |
| 98 | * umtx_sleep { const int *ptr, int value, int timeout } |
| 99 | */ |
| 100 | int |
| 101 | sys_umtx_sleep(struct umtx_sleep_args *uap) |
| 102 | { |
| 103 | struct lwbuf lwb_cache; |
| 104 | struct lwbuf *lwb; |
| 105 | struct vm_page_action action; |
| 106 | vm_page_t m; |
| 107 | void *waddr; |
| 108 | int offset; |
| 109 | int timeout; |
| 110 | int error = EBUSY; |
| 111 | |
| 112 | if (uap->timeout < 0) |
| 113 | return (EINVAL); |
| 114 | if ((vm_offset_t)uap->ptr & (sizeof(int) - 1)) |
| 115 | return (EFAULT); |
| 116 | |
| 117 | /* |
| 118 | * When faulting in the page, force any COW pages to be resolved. |
| 119 | * Otherwise the physical page we sleep on my not match the page |
| 120 | * being woken up. |
| 121 | */ |
| 122 | lwkt_gettoken(&vm_token); |
| 123 | m = vm_fault_page_quick((vm_offset_t)uap->ptr, VM_PROT_READ|VM_PROT_WRITE, &error); |
| 124 | if (m == NULL) { |
| 125 | error = EFAULT; |
| 126 | goto done; |
| 127 | } |
| 128 | lwb = lwbuf_alloc(m, &lwb_cache); |
| 129 | offset = (vm_offset_t)uap->ptr & PAGE_MASK; |
| 130 | |
| 131 | /* |
| 132 | * The critical section is required to interlock the tsleep against |
| 133 | * a wakeup from another cpu. The lfence forces synchronization. |
| 134 | */ |
| 135 | if (*(int *)(lwbuf_kva(lwb) + offset) == uap->value) { |
| 136 | if ((timeout = uap->timeout) != 0) { |
| 137 | timeout = (timeout / 1000000) * hz + |
| 138 | ((timeout % 1000000) * hz + 999999) / 1000000; |
| 139 | } |
| 140 | waddr = (void *)((intptr_t)VM_PAGE_TO_PHYS(m) + offset); |
| 141 | crit_enter(); |
| 142 | tsleep_interlock(waddr, PCATCH | PDOMAIN_UMTX); |
| 143 | if (*(int *)(lwbuf_kva(lwb) + offset) == uap->value) { |
| 144 | vm_page_init_action(m, &action, umtx_sleep_page_action_cow, waddr); |
| 145 | vm_page_register_action(&action, VMEVENT_COW); |
| 146 | error = tsleep(waddr, PCATCH | PINTERLOCKED | PDOMAIN_UMTX, |
| 147 | "umtxsl", timeout); |
| 148 | vm_page_unregister_action(&action); |
| 149 | } else { |
| 150 | error = EBUSY; |
| 151 | } |
| 152 | crit_exit(); |
| 153 | /* Always break out in case of signal, even if restartable */ |
| 154 | if (error == ERESTART) |
| 155 | error = EINTR; |
| 156 | } else { |
| 157 | error = EBUSY; |
| 158 | } |
| 159 | |
| 160 | lwbuf_free(lwb); |
| 161 | /*vm_page_dirty(m); we don't actually dirty the page */ |
| 162 | vm_page_unhold(m); |
| 163 | done: |
| 164 | lwkt_reltoken(&vm_token); |
| 165 | return(error); |
| 166 | } |
| 167 | |
| 168 | /* |
| 169 | * If this page is being copied it may no longer represent the page |
| 170 | * underlying our virtual address. Wake up any umtx_sleep()'s |
| 171 | * that were waiting on its physical address to force them to retry. |
| 172 | */ |
| 173 | static void |
| 174 | umtx_sleep_page_action_cow(vm_page_t m, vm_page_action_t action) |
| 175 | { |
| 176 | lwkt_gettoken(&vm_token); |
| 177 | wakeup_domain(action->data, PDOMAIN_UMTX); |
| 178 | lwkt_reltoken(&vm_token); |
| 179 | } |
| 180 | |
| 181 | /* |
| 182 | * umtx_wakeup { const int *ptr, int count } |
| 183 | * |
| 184 | * Wakeup the specified number of processes held in umtx_sleep() on the |
| 185 | * specified user address. A count of 0 wakes up all waiting processes. |
| 186 | * |
| 187 | * XXX assumes that the physical address space does not exceed the virtual |
| 188 | * address space. |
| 189 | */ |
| 190 | int |
| 191 | sys_umtx_wakeup(struct umtx_wakeup_args *uap) |
| 192 | { |
| 193 | vm_page_t m; |
| 194 | int offset; |
| 195 | int error; |
| 196 | void *waddr; |
| 197 | |
| 198 | cpu_mfence(); |
| 199 | if ((vm_offset_t)uap->ptr & (sizeof(int) - 1)) |
| 200 | return (EFAULT); |
| 201 | lwkt_gettoken(&vm_token); |
| 202 | m = vm_fault_page_quick((vm_offset_t)uap->ptr, VM_PROT_READ, &error); |
| 203 | if (m == NULL) { |
| 204 | error = EFAULT; |
| 205 | goto done; |
| 206 | } |
| 207 | offset = (vm_offset_t)uap->ptr & PAGE_MASK; |
| 208 | waddr = (void *)((intptr_t)VM_PAGE_TO_PHYS(m) + offset); |
| 209 | |
| 210 | if (uap->count == 1) { |
| 211 | wakeup_domain_one(waddr, PDOMAIN_UMTX); |
| 212 | } else { |
| 213 | /* XXX wakes them all up for now */ |
| 214 | wakeup_domain(waddr, PDOMAIN_UMTX); |
| 215 | } |
| 216 | vm_page_unhold(m); |
| 217 | error = 0; |
| 218 | done: |
| 219 | lwkt_reltoken(&vm_token); |
| 220 | return(error); |
| 221 | } |
| 222 | |