1 /* 2 * Copyright (c) 2003,2004 The DragonFly Project. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Matthew Dillon <dillon@backplane.com> and David Xu <davidxu@freebsd.org> 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 3. Neither the name of The DragonFly Project nor the names of its 18 * contributors may be used to endorse or promote products derived 19 * from this software without specific, prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * $DragonFly: src/sys/kern/kern_umtx.c,v 1.7 2007/07/02 01:30:07 dillon Exp $ 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/sfbuf.h> 51 #include <sys/module.h> 52 53 #include <vm/vm.h> 54 #include <vm/vm_param.h> 55 #include <sys/lock.h> 56 #include <vm/pmap.h> 57 #include <vm/vm_map.h> 58 #include <vm/vm_object.h> 59 #include <vm/vm_page.h> 60 #include <vm/vm_pager.h> 61 #include <vm/vm_pageout.h> 62 #include <vm/vm_extern.h> 63 #include <vm/vm_page.h> 64 #include <vm/vm_kern.h> 65 66 /* 67 * If the contents of the userland-supplied pointer matches the specified 68 * value enter an interruptable sleep for up to <timeout> microseconds. 69 * If the contents does not match then return immediately. 70 * 71 * The specified timeout may not exceed 1 second. 72 * 73 * Returns 0 if we slept and were woken up, -1 and ETIMEDOUT if we slept 74 * and timed out, and EBUSY if the contents of the pointer did not match 75 * the specified value. A timeout of 0 indicates an unlimited sleep. 76 * EINTR is returned if the call was interrupted by a signal (even if 77 * the signal specifies that the system call should restart). 78 * 79 * This function interlocks against call to umtx_wakeup. It does NOT interlock 80 * against changes in *ptr. However, it does not have to. The standard use 81 * of *ptr is to differentiate between an uncontested and a contested mutex 82 * and call umtx_wakeup when releasing a contested mutex. Therefore we can 83 * safely race against changes in *ptr as long as we are properly interlocked 84 * against the umtx_wakeup() call. 85 * 86 * The VM page associated with the mutex is held to prevent reuse in order 87 * to guarentee that the physical address remains consistent. 88 * 89 * umtx_sleep { const int *ptr, int value, int timeout } 90 */ 91 int 92 sys_umtx_sleep(struct umtx_sleep_args *uap) 93 { 94 int error = EBUSY; 95 struct sf_buf *sf; 96 vm_page_t m; 97 void *waddr; 98 int offset; 99 int timeout; 100 101 if ((unsigned int)uap->timeout > 1000000) 102 return (EINVAL); 103 if ((vm_offset_t)uap->ptr & (sizeof(int) - 1)) 104 return (EFAULT); 105 m = vm_fault_page_quick((vm_offset_t)uap->ptr, VM_PROT_READ, &error); 106 if (m == NULL) 107 return (EFAULT); 108 sf = sf_buf_alloc(m, SFB_CPUPRIVATE); 109 offset = (vm_offset_t)uap->ptr & PAGE_MASK; 110 111 if (*(int *)(sf_buf_kva(sf) + offset) == uap->value) { 112 if ((timeout = uap->timeout) != 0) 113 timeout = (timeout * hz + 999999) / 1000000; 114 waddr = (void *)((intptr_t)VM_PAGE_TO_PHYS(m) + offset); 115 error = tsleep(waddr, PCATCH|PDOMAIN_UMTX, "umtxsl", timeout); 116 /* Always break out in case of signal, even if restartable */ 117 if (error == ERESTART) 118 error = EINTR; 119 } else { 120 error = EBUSY; 121 } 122 123 sf_buf_free(sf); 124 vm_page_unhold(m); 125 return(error); 126 } 127 128 /* 129 * umtx_wakeup { const int *ptr, int count } 130 * 131 * Wakeup the specified number of processes held in umtx_sleep() on the 132 * specified user address. A count of 0 wakes up all waiting processes. 133 * 134 * XXX assumes that the physical address space does not exceed the virtual 135 * address space. 136 */ 137 int 138 sys_umtx_wakeup(struct umtx_wakeup_args *uap) 139 { 140 vm_page_t m; 141 int offset; 142 int error; 143 void *waddr; 144 145 cpu_mfence(); 146 if ((vm_offset_t)uap->ptr & (sizeof(int) - 1)) 147 return (EFAULT); 148 m = vm_fault_page_quick((vm_offset_t)uap->ptr, VM_PROT_READ, &error); 149 if (m == NULL) 150 return (EFAULT); 151 offset = (vm_offset_t)uap->ptr & PAGE_MASK; 152 waddr = (void *)((intptr_t)VM_PAGE_TO_PHYS(m) + offset); 153 154 if (uap->count == 1) { 155 wakeup_domain_one(waddr, PDOMAIN_UMTX); 156 } else { 157 /* XXX wakes them all up for now */ 158 wakeup_domain(waddr, PDOMAIN_UMTX); 159 } 160 vm_page_unhold(m); 161 return(0); 162 } 163 164