1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
|
/* Hurd helpers for lowlevellocks.
Copyright (C) 1999-2019 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include "hurdlock.h"
#include <hurd.h>
#include <hurd/hurd.h>
#include <time.h>
#include <errno.h>
#include <unistd.h>
/* Convert an absolute timeout in nanoseconds to a relative
timeout in milliseconds. */
static inline int __attribute__ ((gnu_inline))
compute_reltime (const struct timespec *abstime, clockid_t clk)
{
struct timespec ts;
__clock_gettime (clk, &ts);
ts.tv_sec = abstime->tv_sec - ts.tv_sec;
ts.tv_nsec = abstime->tv_nsec - ts.tv_nsec;
if (ts.tv_nsec < 0)
{
--ts.tv_sec;
ts.tv_nsec += 1000000000;
}
return ts.tv_sec < 0 ? -1 : (int)(ts.tv_sec * 1000 + ts.tv_nsec / 1000000);
}
int
__lll_abstimed_wait (void *ptr, int val,
const struct timespec *tsp, int flags, int clk)
{
int mlsec = compute_reltime (tsp, clk);
return mlsec < 0 ? KERN_TIMEDOUT : lll_timed_wait (ptr, val, mlsec, flags);
}
int
__lll_abstimed_xwait (void *ptr, int lo, int hi,
const struct timespec *tsp, int flags, int clk)
{
int mlsec = compute_reltime (tsp, clk);
return mlsec < 0 ? KERN_TIMEDOUT : lll_timed_xwait (ptr, lo, hi, mlsec,
flags);
}
int
__lll_abstimed_lock (void *ptr,
const struct timespec *tsp, int flags, int clk)
{
if (lll_trylock (ptr) == 0)
return 0;
while (1)
{
if (atomic_exchange_acq ((int *)ptr, 2) == 0)
return 0;
else if (tsp->tv_nsec < 0 || tsp->tv_nsec >= 1000000000)
return EINVAL;
int mlsec = compute_reltime (tsp, clk);
if (mlsec < 0 || lll_timed_wait (ptr, 2, mlsec, flags) == KERN_TIMEDOUT)
return ETIMEDOUT;
}
}
/* Robust locks. */
/* Test if a given process id is still valid. */
static inline int
valid_pid (int pid)
{
task_t task = __pid2task (pid);
if (task == MACH_PORT_NULL)
return 0;
__mach_port_deallocate (__mach_task_self (), task);
return 1;
}
/* Robust locks have currently no support from the kernel; they
are simply implemented with periodic polling. When sleeping, the
maximum blocking time is determined by this constant. */
#define MAX_WAIT_TIME 1500
int
__lll_robust_lock (void *ptr, int flags)
{
int *iptr = (int *)ptr;
int id = __getpid ();
int wait_time = 25;
unsigned int val;
/* Try to set the lock word to our PID if it's clear. Otherwise,
mark it as having waiters. */
while (1)
{
val = *iptr;
if (!val && atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0)
return 0;
else if (atomic_compare_and_exchange_bool_acq (iptr,
val | LLL_WAITERS, val) == 0)
break;
}
for (id |= LLL_WAITERS ; ; )
{
val = *iptr;
if (!val && atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0)
return 0;
else if (val && !valid_pid (val & LLL_OWNER_MASK))
{
if (atomic_compare_and_exchange_bool_acq (iptr, id, val) == 0)
return EOWNERDEAD;
}
else
{
lll_timed_wait (iptr, val, wait_time, flags);
if (wait_time < MAX_WAIT_TIME)
wait_time <<= 1;
}
}
}
int
__lll_robust_abstimed_lock (void *ptr,
const struct timespec *tsp, int flags, int clk)
{
int *iptr = (int *)ptr;
int id = __getpid ();
int wait_time = 25;
unsigned int val;
while (1)
{
val = *iptr;
if (!val && atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0)
return 0;
else if (atomic_compare_and_exchange_bool_acq (iptr,
val | LLL_WAITERS, val) == 0)
break;
}
for (id |= LLL_WAITERS ; ; )
{
val = *iptr;
if (!val && atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0)
return 0;
else if (val && !valid_pid (val & LLL_OWNER_MASK))
{
if (atomic_compare_and_exchange_bool_acq (iptr, id, val) == 0)
return EOWNERDEAD;
}
else
{
int mlsec = compute_reltime (tsp, clk);
if (mlsec < 0)
return ETIMEDOUT;
else if (mlsec > wait_time)
mlsec = wait_time;
int res = lll_timed_wait (iptr, val, mlsec, flags);
if (res == KERN_TIMEDOUT)
return ETIMEDOUT;
else if (wait_time < MAX_WAIT_TIME)
wait_time <<= 1;
}
}
}
int
__lll_robust_trylock (void *ptr)
{
int *iptr = (int *)ptr;
int id = __getpid ();
unsigned int val = *iptr;
if (!val)
{
if (atomic_compare_and_exchange_bool_acq (iptr, id, 0) == 0)
return 0;
}
else if (!valid_pid (val & LLL_OWNER_MASK)
&& atomic_compare_and_exchange_bool_acq (iptr, id, val) == 0)
return EOWNERDEAD;
return EBUSY;
}
void
__lll_robust_unlock (void *ptr, int flags)
{
unsigned int val = atomic_load_relaxed ((unsigned int *)ptr);
while (1)
{
if (val & LLL_WAITERS)
{
lll_set_wake (ptr, 0, flags);
break;
}
else if (atomic_compare_exchange_weak_release ((unsigned int *)ptr, &val, 0))
break;
}
}
|
