1 /* Hurd helpers for lowlevellocks.
2 Copyright (C) 1999-2020 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
21 #include <hurd/hurd.h>
26 /* Convert an absolute timeout in nanoseconds to a relative
27 timeout in milliseconds. */
28 static inline int __attribute__ ((gnu_inline
))
29 compute_reltime (const struct timespec
*abstime
, clockid_t clk
)
32 __clock_gettime (clk
, &ts
);
34 ts
.tv_sec
= abstime
->tv_sec
- ts
.tv_sec
;
35 ts
.tv_nsec
= abstime
->tv_nsec
- ts
.tv_nsec
;
40 ts
.tv_nsec
+= 1000000000;
43 return ts
.tv_sec
< 0 ? -1 : (int)(ts
.tv_sec
* 1000 + ts
.tv_nsec
/ 1000000);
47 __lll_abstimed_wait (void *ptr
, int val
,
48 const struct timespec
*tsp
, int flags
, int clk
)
50 if (clk
!= CLOCK_REALTIME
)
53 int mlsec
= compute_reltime (tsp
, clk
);
54 return mlsec
< 0 ? KERN_TIMEDOUT
: lll_timed_wait (ptr
, val
, mlsec
, flags
);
58 __lll_abstimed_xwait (void *ptr
, int lo
, int hi
,
59 const struct timespec
*tsp
, int flags
, int clk
)
61 if (clk
!= CLOCK_REALTIME
)
64 int mlsec
= compute_reltime (tsp
, clk
);
65 return mlsec
< 0 ? KERN_TIMEDOUT
: lll_timed_xwait (ptr
, lo
, hi
, mlsec
,
70 __lll_abstimed_lock (void *ptr
,
71 const struct timespec
*tsp
, int flags
, int clk
)
73 if (clk
!= CLOCK_REALTIME
)
76 if (lll_trylock (ptr
) == 0)
81 if (atomic_exchange_acq ((int *)ptr
, 2) == 0)
83 else if (! valid_nanoseconds (tsp
->tv_nsec
))
86 int mlsec
= compute_reltime (tsp
, clk
);
87 if (mlsec
< 0 || lll_timed_wait (ptr
, 2, mlsec
, flags
) == KERN_TIMEDOUT
)
94 /* Test if a given process id is still valid. */
98 task_t task
= __pid2task (pid
);
99 if (task
== MACH_PORT_NULL
)
102 __mach_port_deallocate (__mach_task_self (), task
);
106 /* Robust locks have currently no support from the kernel; they
107 are simply implemented with periodic polling. When sleeping, the
108 maximum blocking time is determined by this constant. */
109 #define MAX_WAIT_TIME 1500
112 __lll_robust_lock (void *ptr
, int flags
)
114 int *iptr
= (int *)ptr
;
115 int id
= __getpid ();
119 /* Try to set the lock word to our PID if it's clear. Otherwise,
120 mark it as having waiters. */
124 if (!val
&& atomic_compare_and_exchange_bool_acq (iptr
, id
, 0) == 0)
126 else if (atomic_compare_and_exchange_bool_acq (iptr
,
127 val
| LLL_WAITERS
, val
) == 0)
131 for (id
|= LLL_WAITERS
; ; )
134 if (!val
&& atomic_compare_and_exchange_bool_acq (iptr
, id
, 0) == 0)
136 else if (val
&& !valid_pid (val
& LLL_OWNER_MASK
))
138 if (atomic_compare_and_exchange_bool_acq (iptr
, id
, val
) == 0)
143 lll_timed_wait (iptr
, val
, wait_time
, flags
);
144 if (wait_time
< MAX_WAIT_TIME
)
151 __lll_robust_abstimed_lock (void *ptr
,
152 const struct timespec
*tsp
, int flags
, int clk
)
154 int *iptr
= (int *)ptr
;
155 int id
= __getpid ();
159 if (clk
!= CLOCK_REALTIME
)
165 if (!val
&& atomic_compare_and_exchange_bool_acq (iptr
, id
, 0) == 0)
167 else if (atomic_compare_and_exchange_bool_acq (iptr
,
168 val
| LLL_WAITERS
, val
) == 0)
172 for (id
|= LLL_WAITERS
; ; )
175 if (!val
&& atomic_compare_and_exchange_bool_acq (iptr
, id
, 0) == 0)
177 else if (val
&& !valid_pid (val
& LLL_OWNER_MASK
))
179 if (atomic_compare_and_exchange_bool_acq (iptr
, id
, val
) == 0)
184 int mlsec
= compute_reltime (tsp
, clk
);
187 else if (mlsec
> wait_time
)
190 int res
= lll_timed_wait (iptr
, val
, mlsec
, flags
);
191 if (res
== KERN_TIMEDOUT
)
193 else if (wait_time
< MAX_WAIT_TIME
)
200 __lll_robust_trylock (void *ptr
)
202 int *iptr
= (int *)ptr
;
203 int id
= __getpid ();
204 unsigned int val
= *iptr
;
208 if (atomic_compare_and_exchange_bool_acq (iptr
, id
, 0) == 0)
211 else if (!valid_pid (val
& LLL_OWNER_MASK
)
212 && atomic_compare_and_exchange_bool_acq (iptr
, id
, val
) == 0)
219 __lll_robust_unlock (void *ptr
, int flags
)
221 unsigned int val
= atomic_load_relaxed ((unsigned int *)ptr
);
224 if (val
& LLL_WAITERS
)
226 lll_set_wake (ptr
, 0, flags
);
229 else if (atomic_compare_exchange_weak_release ((unsigned int *)ptr
, &val
, 0))