sys/kern/kern_umtx.c

   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