4 * Copyright (c) 2003,2004,2010 The DragonFly Project. All rights reserved.
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>
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
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
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.
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,
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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
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.
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>
52 #include <cpu/lwbuf.h>
55 #include <vm/vm_param.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>
66 #include <vm/vm_page2.h>
68 #include <machine/vmm.h>
70 static void umtx_sleep_page_action_cow(vm_page_t m
, vm_page_action_t action
);
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.
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).
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.
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.
97 * umtx_sleep { const int *ptr, int value, int timeout }
100 sys_umtx_sleep(struct umtx_sleep_args
*uap
)
102 struct lwbuf lwb_cache
;
104 struct vm_page_action action
;
111 if (uap
->timeout
< 0)
114 if (curthread
->td_vmm
) {
116 vmm_vm_get_gpa(curproc
, &gpa
, (register_t
) uap
->ptr
);
117 uap
->ptr
= (const int *)gpa
;
120 if ((vm_offset_t
)uap
->ptr
& (sizeof(int) - 1))
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
128 m
= vm_fault_page_quick((vm_offset_t
)uap
->ptr
,
129 VM_PROT_READ
|VM_PROT_WRITE
, &error
);
134 lwb
= lwbuf_alloc(m
, &lwb_cache
);
135 offset
= (vm_offset_t
)uap
->ptr
& PAGE_MASK
;
138 * The critical section is required to interlock the tsleep against
139 * a wakeup from another cpu. The lfence forces synchronization.
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;
146 waddr
= (void *)((intptr_t)VM_PAGE_TO_PHYS(m
) + offset
);
148 tsleep_interlock(waddr
, PCATCH
| PDOMAIN_UMTX
);
149 if (*(int *)(lwbuf_kva(lwb
) + offset
) == uap
->value
) {
150 vm_page_init_action(m
, &action
, umtx_sleep_page_action_cow
, waddr
);
151 vm_page_register_action(&action
, VMEVENT_COW
);
152 if (*(int *)(lwbuf_kva(lwb
) + offset
) == uap
->value
) {
153 error
= tsleep(waddr
, PCATCH
| PINTERLOCKED
| PDOMAIN_UMTX
,
158 vm_page_unregister_action(&action
);
163 /* Always break out in case of signal, even if restartable */
164 if (error
== ERESTART
)
171 /*vm_page_dirty(m); we don't actually dirty the page */
178 * If this page is being copied it may no longer represent the page
179 * underlying our virtual address. Wake up any umtx_sleep()'s
180 * that were waiting on its physical address to force them to retry.
183 umtx_sleep_page_action_cow(vm_page_t m
, vm_page_action_t action
)
185 wakeup_domain(action
->data
, PDOMAIN_UMTX
);
189 * umtx_wakeup { const int *ptr, int count }
191 * Wakeup the specified number of processes held in umtx_sleep() on the
192 * specified user address. A count of 0 wakes up all waiting processes.
194 * XXX assumes that the physical address space does not exceed the virtual
198 sys_umtx_wakeup(struct umtx_wakeup_args
*uap
)
205 if (curthread
->td_vmm
) {
207 vmm_vm_get_gpa(curproc
, &gpa
, (register_t
) uap
->ptr
);
208 uap
->ptr
= (const int *)gpa
;
212 if ((vm_offset_t
)uap
->ptr
& (sizeof(int) - 1))
214 m
= vm_fault_page_quick((vm_offset_t
)uap
->ptr
, VM_PROT_READ
, &error
);
219 offset
= (vm_offset_t
)uap
->ptr
& PAGE_MASK
;
220 waddr
= (void *)((intptr_t)VM_PAGE_TO_PHYS(m
) + offset
);
222 if (uap
->count
== 1) {
223 wakeup_domain_one(waddr
, PDOMAIN_UMTX
);
225 /* XXX wakes them all up for now */
226 wakeup_domain(waddr
, PDOMAIN_UMTX
);