mirror of
http://git.haproxy.org/git/haproxy.git/
synced 2024-12-27 23:22:09 +00:00
7c69c9b51f
When EBO was brought to pl_take_w() by plock commit 60d750d ("plock: use
EBO when waiting for readers to leave in take_w() and stow()"), a mistake
was made: the mask against which the current value of the lock is tested
excludes the first reader like in stow(), but it must not because it was
just obtained via an ldadd() which means that it doesn't count itself.
The problem this causes is that if there is exactly one reader when a
writer grabs the lock, the writer will not wait for it to leave before
starting its operations.
The solution consists in checking for any reader in the IF. However the
mask passed to pl_wait_unlock_*() must still exclude the lowest bit as
it's verified after a subsequent load.
Kudos to Remi Tricot-Le Breton for reporting and bisecting this issue
with a reproducer.
No backport is needed since this was brought in 2.9-dev3 with commit
8178a5211 ("MAJOR: threads/plock: update the embedded library again").
The code is now on par with plock commit ada70fe.
1423 lines
87 KiB
C
1423 lines
87 KiB
C
/* plock - progressive locks
|
|
*
|
|
* Copyright (C) 2012-2017 Willy Tarreau <w@1wt.eu>
|
|
*
|
|
* Permission is hereby granted, free of charge, to any person obtaining
|
|
* a copy of this software and associated documentation files (the
|
|
* "Software"), to deal in the Software without restriction, including
|
|
* without limitation the rights to use, copy, modify, merge, publish,
|
|
* distribute, sublicense, and/or sell copies of the Software, and to
|
|
* permit persons to whom the Software is furnished to do so, subject to
|
|
* the following conditions:
|
|
*
|
|
* The above copyright notice and this permission notice shall be
|
|
* included in all copies or substantial portions of the Software.
|
|
*
|
|
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
|
|
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
|
|
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
|
|
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
|
|
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
|
|
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
|
|
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
|
|
* OTHER DEALINGS IN THE SOFTWARE.
|
|
*/
|
|
|
|
#ifndef PL_PLOCK_H
|
|
#define PL_PLOCK_H
|
|
|
|
#include "atomic-ops.h"
|
|
#ifdef _POSIX_PRIORITY_SCHEDULING
|
|
#include <sched.h>
|
|
#endif
|
|
|
|
/* 64 bit */
|
|
#define PLOCK64_RL_1 0x0000000000000004ULL
|
|
#define PLOCK64_RL_2PL 0x00000000FFFFFFF8ULL
|
|
#define PLOCK64_RL_ANY 0x00000000FFFFFFFCULL
|
|
#define PLOCK64_SL_1 0x0000000100000000ULL
|
|
#define PLOCK64_SL_ANY 0x0000000300000000ULL
|
|
#define PLOCK64_WL_1 0x0000000400000000ULL
|
|
#define PLOCK64_WL_2PL 0xFFFFFFF800000000ULL
|
|
#define PLOCK64_WL_ANY 0xFFFFFFFC00000000ULL
|
|
|
|
/* 32 bit */
|
|
#define PLOCK32_RL_1 0x00000004
|
|
#define PLOCK32_RL_2PL 0x0000FFF8
|
|
#define PLOCK32_RL_ANY 0x0000FFFC
|
|
#define PLOCK32_SL_1 0x00010000
|
|
#define PLOCK32_SL_ANY 0x00030000
|
|
#define PLOCK32_WL_1 0x00040000
|
|
#define PLOCK32_WL_2PL 0xFFF80000
|
|
#define PLOCK32_WL_ANY 0xFFFC0000
|
|
|
|
/* dereferences <*p> as unsigned long without causing aliasing issues */
|
|
#define pl_deref_long(p) ({ volatile unsigned long *__pl_l = (unsigned long *)(p); *__pl_l; })
|
|
|
|
/* dereferences <*p> as unsigned int without causing aliasing issues */
|
|
#define pl_deref_int(p) ({ volatile unsigned int *__pl_i = (unsigned int *)(p); *__pl_i; })
|
|
|
|
/* This function waits for <lock> to release all bits covered by <mask>, and
|
|
* enforces an exponential backoff using CPU pauses to limit the pollution to
|
|
* the other threads' caches. The progression follows (1.5^N)-1, limited to
|
|
* 16384 iterations, which is way sufficient even for very large numbers of
|
|
* threads. It's possible to disable exponential backoff (EBO) for debugging
|
|
* purposes by setting PLOCK_DISABLE_EBO, in which case the function will be
|
|
* replaced with a simpler macro. This may for example be useful to more
|
|
* easily track callers' CPU usage. The macro was not designed to be used
|
|
* outside of the functions defined here.
|
|
*/
|
|
#if defined(PLOCK_DISABLE_EBO)
|
|
#define pl_wait_unlock_long(lock, mask) \
|
|
({ \
|
|
unsigned long _r; \
|
|
do { \
|
|
pl_cpu_relax(); \
|
|
_r = pl_deref_long(lock); \
|
|
} while (_r & mask); \
|
|
_r; /* return value */ \
|
|
})
|
|
#else /* not PLOCK_DISABLE_EBO */
|
|
__attribute__((unused,always_inline,no_instrument_function)) inline
|
|
static unsigned long __pl_wait_unlock_long(const unsigned long *lock, const unsigned long mask)
|
|
{
|
|
unsigned long ret;
|
|
unsigned int m = 0;
|
|
|
|
do {
|
|
unsigned int loops = m;
|
|
|
|
#ifdef _POSIX_PRIORITY_SCHEDULING
|
|
if (loops >= 65536) {
|
|
sched_yield();
|
|
loops -= 32768;
|
|
}
|
|
#endif
|
|
for (; loops >= 60; loops --)
|
|
pl_cpu_relax();
|
|
|
|
for (; loops >= 1; loops--)
|
|
pl_barrier();
|
|
|
|
ret = pl_load(lock);
|
|
if (__builtin_expect(ret & mask, 0) == 0)
|
|
break;
|
|
|
|
/* the below produces an exponential growth with loops to lower
|
|
* values and still growing. This allows competing threads to
|
|
* wait different times once the threshold is reached.
|
|
*/
|
|
m = ((m + (m >> 1)) + 2) & 0x3ffff;
|
|
} while (1);
|
|
|
|
return ret;
|
|
}
|
|
|
|
# if defined(PLOCK_INLINE_EBO)
|
|
__attribute__((unused,always_inline,no_instrument_function)) inline
|
|
# else
|
|
__attribute__((unused,noinline,no_instrument_function))
|
|
# endif
|
|
static unsigned long pl_wait_unlock_long(const unsigned long *lock, const unsigned long mask)
|
|
{
|
|
return __pl_wait_unlock_long(lock, mask);
|
|
}
|
|
#endif /* PLOCK_DISABLE_EBO */
|
|
|
|
/* This function waits for <lock> to release all bits covered by <mask>, and
|
|
* enforces an exponential backoff using CPU pauses to limit the pollution to
|
|
* the other threads' caches. The progression follows (2^N)-1, limited to 255
|
|
* iterations, which is way sufficient even for very large numbers of threads.
|
|
* The function slightly benefits from size optimization under gcc, but Clang
|
|
* cannot do it, so it's not done here, as it doesn't make a big difference.
|
|
* It is possible to disable exponential backoff (EBO) for debugging purposes
|
|
* by setting PLOCK_DISABLE_EBO, in which case the function will be replaced
|
|
* with a simpler macro. This may for example be useful to more easily track
|
|
* callers' CPU usage. The macro was not designed to be used outside of the
|
|
* functions defined here.
|
|
*/
|
|
#if defined(PLOCK_DISABLE_EBO)
|
|
#define pl_wait_unlock_int(lock, mask) \
|
|
({ \
|
|
unsigned int _r; \
|
|
do { \
|
|
pl_cpu_relax(); \
|
|
_r = pl_deref_int(lock); \
|
|
} while (_r & mask); \
|
|
_r; /* return value */ \
|
|
})
|
|
#else
|
|
__attribute__((unused,always_inline,no_instrument_function)) inline
|
|
static unsigned int __pl_wait_unlock_int(const unsigned int *lock, const unsigned int mask)
|
|
{
|
|
unsigned int ret;
|
|
unsigned int m = 0;
|
|
|
|
do {
|
|
unsigned int loops = m;
|
|
|
|
#ifdef _POSIX_PRIORITY_SCHEDULING
|
|
if (loops >= 65536) {
|
|
sched_yield();
|
|
loops -= 32768;
|
|
}
|
|
#endif
|
|
for (; loops >= 200; loops -= 10)
|
|
pl_cpu_relax();
|
|
|
|
for (; loops >= 1; loops--)
|
|
pl_barrier();
|
|
|
|
ret = pl_deref_int(lock);
|
|
if (__builtin_expect(ret & mask, 0) == 0)
|
|
break;
|
|
|
|
/* the below produces an exponential growth with loops to lower
|
|
* values and still growing. This allows competing threads to
|
|
* wait different times once the threshold is reached.
|
|
*/
|
|
m = ((m + (m >> 1)) + 2) & 0x3ffff;
|
|
} while (1);
|
|
|
|
return ret;
|
|
}
|
|
|
|
# if defined(PLOCK_INLINE_EBO)
|
|
__attribute__((unused,always_inline,no_instrument_function)) inline
|
|
# else
|
|
__attribute__((unused,noinline,no_instrument_function))
|
|
# endif
|
|
static unsigned int pl_wait_unlock_int(const unsigned int *lock, const unsigned int mask)
|
|
{
|
|
return __pl_wait_unlock_int(lock, mask);
|
|
}
|
|
#endif /* PLOCK_DISABLE_EBO */
|
|
|
|
/* This function waits for <lock> to change from value <prev> and returns the
|
|
* new value. It enforces an exponential backoff using CPU pauses to limit the
|
|
* pollution to the other threads' caches. The progression follows (2^N)-1,
|
|
* limited to 255 iterations, which is way sufficient even for very large
|
|
* numbers of threads. It is designed to be called after a first test which
|
|
* retrieves the previous value, so it starts by waiting. The function slightly
|
|
* benefits from size optimization under gcc, but Clang cannot do it, so it's
|
|
* not done here, as it doesn't make a big difference.
|
|
*/
|
|
__attribute__((unused,noinline,no_instrument_function))
|
|
static unsigned long pl_wait_new_long(const unsigned long *lock, const unsigned long prev)
|
|
{
|
|
unsigned char m = 0;
|
|
unsigned long curr;
|
|
|
|
do {
|
|
unsigned char loops = m + 1;
|
|
m = (m << 1) + 1;
|
|
do {
|
|
pl_cpu_relax();
|
|
} while (__builtin_expect(--loops, 0));
|
|
curr = pl_deref_long(lock);
|
|
} while (__builtin_expect(curr == prev, 0));
|
|
return curr;
|
|
}
|
|
|
|
/* This function waits for <lock> to change from value <prev> and returns the
|
|
* new value. It enforces an exponential backoff using CPU pauses to limit the
|
|
* pollution to the other threads' caches. The progression follows (2^N)-1,
|
|
* limited to 255 iterations, which is way sufficient even for very large
|
|
* numbers of threads. It is designed to be called after a first test which
|
|
* retrieves the previous value, so it starts by waiting. The function slightly
|
|
* benefits from size optimization under gcc, but Clang cannot do it, so it's
|
|
* not done here, as it doesn't make a big difference.
|
|
*/
|
|
__attribute__((unused,noinline,no_instrument_function))
|
|
static unsigned int pl_wait_new_int(const unsigned int *lock, const unsigned int prev)
|
|
{
|
|
unsigned char m = 0;
|
|
unsigned int curr;
|
|
|
|
do {
|
|
unsigned char loops = m + 1;
|
|
m = (m << 1) + 1;
|
|
do {
|
|
pl_cpu_relax();
|
|
} while (__builtin_expect(--loops, 0));
|
|
curr = pl_deref_int(lock);
|
|
} while (__builtin_expect(curr == prev, 0));
|
|
return curr;
|
|
}
|
|
|
|
/* request shared read access (R), return non-zero on success, otherwise 0 */
|
|
#define pl_try_r(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long __pl_r = pl_deref_long(lock) & PLOCK64_WL_ANY; \
|
|
pl_barrier(); \
|
|
if (!__builtin_expect(__pl_r, 0)) { \
|
|
__pl_r = pl_ldadd_acq((lock), PLOCK64_RL_1) & PLOCK64_WL_ANY; \
|
|
if (__builtin_expect(__pl_r, 0)) \
|
|
pl_sub_noret((lock), PLOCK64_RL_1); \
|
|
} \
|
|
!__pl_r; /* return value */ \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int __pl_r = pl_deref_int(lock) & PLOCK32_WL_ANY; \
|
|
pl_barrier(); \
|
|
if (!__builtin_expect(__pl_r, 0)) { \
|
|
__pl_r = pl_ldadd_acq((lock), PLOCK32_RL_1) & PLOCK32_WL_ANY; \
|
|
if (__builtin_expect(__pl_r, 0)) \
|
|
pl_sub_noret((lock), PLOCK32_RL_1); \
|
|
} \
|
|
!__pl_r; /* return value */ \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_try_r__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_try_r__(__FILE__,__LINE__); \
|
|
0; \
|
|
}) \
|
|
)
|
|
|
|
/* request shared read access (R) and wait for it. In order not to disturb a W
|
|
* lock waiting for all readers to leave, we first check if a W lock is held
|
|
* before trying to claim the R lock.
|
|
*/
|
|
#define pl_take_r(lock) \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long *__lk_r = (unsigned long *)(lock); \
|
|
register unsigned long __set_r = PLOCK64_RL_1; \
|
|
register unsigned long __msk_r = PLOCK64_WL_ANY; \
|
|
register unsigned long __old_r = pl_cmpxchg(__lk_r, 0, __set_r); \
|
|
if (__old_r) { \
|
|
while (1) { \
|
|
if (__old_r & __msk_r) \
|
|
pl_wait_unlock_long(__lk_r, __msk_r); \
|
|
if (!(pl_ldadd_acq(__lk_r, __set_r) & __msk_r)) \
|
|
break; \
|
|
__old_r = pl_sub_lax(__lk_r, __set_r); \
|
|
} \
|
|
} \
|
|
pl_barrier(); \
|
|
0; \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int *__lk_r = (unsigned int *)(lock); \
|
|
register unsigned int __set_r = PLOCK32_RL_1; \
|
|
register unsigned int __msk_r = PLOCK32_WL_ANY; \
|
|
register unsigned int __old_r = pl_cmpxchg(__lk_r, 0, __set_r); \
|
|
if (__old_r) { \
|
|
while (1) { \
|
|
if (__old_r & __msk_r) \
|
|
pl_wait_unlock_int(__lk_r, __msk_r); \
|
|
if (!(pl_ldadd_acq(__lk_r, __set_r) & __msk_r)) \
|
|
break; \
|
|
__old_r = pl_sub_lax(__lk_r, __set_r); \
|
|
} \
|
|
} \
|
|
pl_barrier(); \
|
|
0; \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_take_r__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_take_r__(__FILE__,__LINE__); \
|
|
0; \
|
|
})
|
|
|
|
/* release the read access (R) lock */
|
|
#define pl_drop_r(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret_rel(lock, PLOCK64_RL_1); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret_rel(lock, PLOCK32_RL_1); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_drop_r__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_drop_r__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* request a seek access (S), return non-zero on success, otherwise 0 */
|
|
#define pl_try_s(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long __pl_r = pl_deref_long(lock); \
|
|
pl_barrier(); \
|
|
if (!__builtin_expect(__pl_r & (PLOCK64_WL_ANY | PLOCK64_SL_ANY), 0)) { \
|
|
__pl_r = pl_ldadd_acq((lock), PLOCK64_SL_1 | PLOCK64_RL_1) & \
|
|
(PLOCK64_WL_ANY | PLOCK64_SL_ANY); \
|
|
if (__builtin_expect(__pl_r, 0)) \
|
|
pl_sub_noret_lax((lock), PLOCK64_SL_1 | PLOCK64_RL_1); \
|
|
} \
|
|
!__pl_r; /* return value */ \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int __pl_r = pl_deref_int(lock); \
|
|
pl_barrier(); \
|
|
if (!__builtin_expect(__pl_r & (PLOCK32_WL_ANY | PLOCK32_SL_ANY), 0)) { \
|
|
__pl_r = pl_ldadd_acq((lock), PLOCK32_SL_1 | PLOCK32_RL_1) & \
|
|
(PLOCK32_WL_ANY | PLOCK32_SL_ANY); \
|
|
if (__builtin_expect(__pl_r, 0)) \
|
|
pl_sub_noret_lax((lock), PLOCK32_SL_1 | PLOCK32_RL_1); \
|
|
} \
|
|
!__pl_r; /* return value */ \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_try_s__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_try_s__(__FILE__,__LINE__); \
|
|
0; \
|
|
}) \
|
|
)
|
|
|
|
/* request a seek access (S) and wait for it. The lock is immediately claimed,
|
|
* and only upon failure an exponential backoff is used. S locks rarely compete
|
|
* with W locks so S will generally not disturb W. As the S lock may be used as
|
|
* a spinlock, it's important to grab it as fast as possible.
|
|
*/
|
|
#define pl_take_s(lock) \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long *__lk_r = (unsigned long *)(lock); \
|
|
register unsigned long __set_r = PLOCK64_SL_1 | PLOCK64_RL_1; \
|
|
register unsigned long __msk_r = PLOCK64_WL_ANY | PLOCK64_SL_ANY; \
|
|
while (1) { \
|
|
if (!__builtin_expect(pl_ldadd_acq(__lk_r, __set_r) & __msk_r, 0)) \
|
|
break; \
|
|
pl_sub_noret_lax(__lk_r, __set_r); \
|
|
pl_wait_unlock_long(__lk_r, __msk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
0; \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int *__lk_r = (unsigned int *)(lock); \
|
|
register unsigned int __set_r = PLOCK32_SL_1 | PLOCK32_RL_1; \
|
|
register unsigned int __msk_r = PLOCK32_WL_ANY | PLOCK32_SL_ANY; \
|
|
while (1) { \
|
|
if (!__builtin_expect(pl_ldadd_acq(__lk_r, __set_r) & __msk_r, 0)) \
|
|
break; \
|
|
pl_sub_noret_lax(__lk_r, __set_r); \
|
|
pl_wait_unlock_int(__lk_r, __msk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
0; \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_take_s__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_take_s__(__FILE__,__LINE__); \
|
|
0; \
|
|
})
|
|
|
|
/* release the seek access (S) lock */
|
|
#define pl_drop_s(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret_rel(lock, PLOCK64_SL_1 + PLOCK64_RL_1); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret_rel(lock, PLOCK32_SL_1 + PLOCK32_RL_1); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_drop_s__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_drop_s__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* drop the S lock and go back to the R lock */
|
|
#define pl_stor(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret(lock, PLOCK64_SL_1); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret(lock, PLOCK32_SL_1); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_stor__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_stor__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* take the W lock under the S lock */
|
|
#define pl_stow(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long __pl_r = pl_ldadd((lock), PLOCK64_WL_1); \
|
|
if (__pl_r & (PLOCK64_RL_ANY & ~PLOCK64_RL_1)) \
|
|
__pl_r = pl_wait_unlock_long((const unsigned long*)lock, (PLOCK64_RL_ANY & ~PLOCK64_RL_1)); \
|
|
pl_barrier(); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int __pl_r = pl_ldadd((lock), PLOCK32_WL_1); \
|
|
if (__pl_r & (PLOCK32_RL_ANY & ~PLOCK32_RL_1)) \
|
|
__pl_r = pl_wait_unlock_int((const unsigned int*)lock, (PLOCK32_RL_ANY & ~PLOCK32_RL_1)); \
|
|
pl_barrier(); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_stow__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_stow__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* drop the W lock and go back to the S lock */
|
|
#define pl_wtos(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret(lock, PLOCK64_WL_1); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret(lock, PLOCK32_WL_1); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_wtos__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_wtos__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* drop the W lock and go back to the R lock */
|
|
#define pl_wtor(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret(lock, PLOCK64_WL_1 | PLOCK64_SL_1); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret(lock, PLOCK32_WL_1 | PLOCK32_SL_1); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_wtor__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_wtor__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* request a write access (W), return non-zero on success, otherwise 0.
|
|
*
|
|
* Below there is something important : by taking both W and S, we will cause
|
|
* an overflow of W at 4/5 of the maximum value that can be stored into W due
|
|
* to the fact that S is 2 bits, so we're effectively adding 5 to the word
|
|
* composed by W:S. But for all words multiple of 4 bits, the maximum value is
|
|
* multiple of 15 thus of 5. So the largest value we can store with all bits
|
|
* set to one will be met by adding 5, and then adding 5 again will place value
|
|
* 1 in W and value 0 in S, so we never leave W with 0. Also, even upon such an
|
|
* overflow, there's no risk to confuse it with an atomic lock because R is not
|
|
* null since it will not have overflown. For 32-bit locks, this situation
|
|
* happens when exactly 13108 threads try to grab the lock at once, W=1, S=0
|
|
* and R=13108. For 64-bit locks, it happens at 858993460 concurrent writers
|
|
* where W=1, S=0 and R=858993460.
|
|
*/
|
|
#define pl_try_w(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long __pl_r = pl_deref_long(lock); \
|
|
pl_barrier(); \
|
|
if (!__builtin_expect(__pl_r & (PLOCK64_WL_ANY | PLOCK64_SL_ANY), 0)) { \
|
|
__pl_r = pl_ldadd_acq((lock), PLOCK64_WL_1 | PLOCK64_SL_1 | PLOCK64_RL_1);\
|
|
if (__builtin_expect(__pl_r & (PLOCK64_WL_ANY | PLOCK64_SL_ANY), 0)) { \
|
|
/* a writer, seeker or atomic is present, let's leave */ \
|
|
pl_sub_noret_lax((lock), PLOCK64_WL_1 | PLOCK64_SL_1 | PLOCK64_RL_1);\
|
|
__pl_r &= (PLOCK64_WL_ANY | PLOCK64_SL_ANY); /* return value */\
|
|
} else { \
|
|
/* wait for all other readers to leave */ \
|
|
while (__pl_r) \
|
|
__pl_r = pl_deref_long(lock) - \
|
|
(PLOCK64_WL_1 | PLOCK64_SL_1 | PLOCK64_RL_1); \
|
|
} \
|
|
} \
|
|
!__pl_r; /* return value */ \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int __pl_r = pl_deref_int(lock); \
|
|
pl_barrier(); \
|
|
if (!__builtin_expect(__pl_r & (PLOCK32_WL_ANY | PLOCK32_SL_ANY), 0)) { \
|
|
__pl_r = pl_ldadd_acq((lock), PLOCK32_WL_1 | PLOCK32_SL_1 | PLOCK32_RL_1);\
|
|
if (__builtin_expect(__pl_r & (PLOCK32_WL_ANY | PLOCK32_SL_ANY), 0)) { \
|
|
/* a writer, seeker or atomic is present, let's leave */ \
|
|
pl_sub_noret_lax((lock), PLOCK32_WL_1 | PLOCK32_SL_1 | PLOCK32_RL_1);\
|
|
__pl_r &= (PLOCK32_WL_ANY | PLOCK32_SL_ANY); /* return value */\
|
|
} else { \
|
|
/* wait for all other readers to leave */ \
|
|
while (__pl_r) \
|
|
__pl_r = pl_deref_int(lock) - \
|
|
(PLOCK32_WL_1 | PLOCK32_SL_1 | PLOCK32_RL_1); \
|
|
} \
|
|
} \
|
|
!__pl_r; /* return value */ \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_try_w__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_try_w__(__FILE__,__LINE__); \
|
|
0; \
|
|
}) \
|
|
)
|
|
|
|
/* request a write access (W) and wait for it. The lock is immediately claimed,
|
|
* and only upon failure an exponential backoff is used.
|
|
*/
|
|
#define pl_take_w(lock) \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long *__lk_r = (unsigned long *)(lock); \
|
|
register unsigned long __set_r = PLOCK64_WL_1 | PLOCK64_SL_1 | PLOCK64_RL_1; \
|
|
register unsigned long __msk_r = PLOCK64_WL_ANY | PLOCK64_SL_ANY; \
|
|
register unsigned long __pl_r; \
|
|
while (1) { \
|
|
__pl_r = pl_ldadd_acq(__lk_r, __set_r); \
|
|
if (!__builtin_expect(__pl_r & __msk_r, 0)) \
|
|
break; \
|
|
pl_sub_noret_lax(__lk_r, __set_r); \
|
|
__pl_r = pl_wait_unlock_long(__lk_r, __msk_r); \
|
|
} \
|
|
/* wait for all other readers to leave */ \
|
|
if (__builtin_expect(__pl_r & PLOCK64_RL_ANY, 0)) \
|
|
__pl_r = pl_wait_unlock_long(__lk_r, (PLOCK64_RL_ANY & ~PLOCK64_RL_1)) - __set_r; \
|
|
pl_barrier(); \
|
|
0; \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int *__lk_r = (unsigned int *)(lock); \
|
|
register unsigned int __set_r = PLOCK32_WL_1 | PLOCK32_SL_1 | PLOCK32_RL_1; \
|
|
register unsigned int __msk_r = PLOCK32_WL_ANY | PLOCK32_SL_ANY; \
|
|
register unsigned int __pl_r; \
|
|
while (1) { \
|
|
__pl_r = pl_ldadd_acq(__lk_r, __set_r); \
|
|
if (!__builtin_expect(__pl_r & __msk_r, 0)) \
|
|
break; \
|
|
pl_sub_noret_lax(__lk_r, __set_r); \
|
|
__pl_r = pl_wait_unlock_int(__lk_r, __msk_r); \
|
|
} \
|
|
/* wait for all other readers to leave */ \
|
|
if (__builtin_expect(__pl_r & PLOCK32_RL_ANY, 0)) \
|
|
__pl_r = pl_wait_unlock_int(__lk_r, (PLOCK32_RL_ANY & ~PLOCK32_RL_1)) - __set_r; \
|
|
pl_barrier(); \
|
|
0; \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_take_w__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_take_w__(__FILE__,__LINE__); \
|
|
0; \
|
|
})
|
|
|
|
/* drop the write (W) lock entirely */
|
|
#define pl_drop_w(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret_rel(lock, PLOCK64_WL_1 | PLOCK64_SL_1 | PLOCK64_RL_1); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret_rel(lock, PLOCK32_WL_1 | PLOCK32_SL_1 | PLOCK32_RL_1); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_drop_w__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_drop_w__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* Try to upgrade from R to S, return non-zero on success, otherwise 0.
|
|
* This lock will fail if S or W are already held. In case of failure to grab
|
|
* the lock, it MUST NOT be retried without first dropping R, or it may never
|
|
* complete due to S waiting for R to leave before upgrading to W.
|
|
*/
|
|
#define pl_try_rtos(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long __pl_r; \
|
|
__pl_r = pl_ldadd_acq((lock), PLOCK64_SL_1) & (PLOCK64_WL_ANY | PLOCK64_SL_ANY);\
|
|
if (__builtin_expect(__pl_r, 0)) \
|
|
pl_sub_noret_lax((lock), PLOCK64_SL_1); \
|
|
!__pl_r; /* return value */ \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int __pl_r; \
|
|
__pl_r = pl_ldadd_acq((lock), PLOCK32_SL_1) & (PLOCK32_WL_ANY | PLOCK32_SL_ANY);\
|
|
if (__builtin_expect(__pl_r, 0)) \
|
|
pl_sub_noret_lax((lock), PLOCK32_SL_1); \
|
|
!__pl_r; /* return value */ \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_try_rtos__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_try_rtos__(__FILE__,__LINE__); \
|
|
0; \
|
|
}) \
|
|
)
|
|
|
|
|
|
/* Try to upgrade from R to W, return non-zero on success, otherwise 0.
|
|
* This lock will fail if S or W are already held. In case of failure to grab
|
|
* the lock, it MUST NOT be retried without first dropping R, or it may never
|
|
* complete due to S waiting for R to leave before upgrading to W. It waits for
|
|
* the last readers to leave.
|
|
*/
|
|
#define pl_try_rtow(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long *__lk_r = (unsigned long *)(lock); \
|
|
register unsigned long __set_r = PLOCK64_WL_1 | PLOCK64_SL_1; \
|
|
register unsigned long __msk_r = PLOCK64_WL_ANY | PLOCK64_SL_ANY; \
|
|
register unsigned long __pl_r; \
|
|
pl_barrier(); \
|
|
while (1) { \
|
|
__pl_r = pl_ldadd_acq(__lk_r, __set_r); \
|
|
if (__builtin_expect(__pl_r & __msk_r, 0)) { \
|
|
if (pl_ldadd_lax(__lk_r, - __set_r)) \
|
|
break; /* the caller needs to drop the lock now */ \
|
|
continue; /* lock was released, try again */ \
|
|
} \
|
|
/* ok we're the only writer, wait for readers to leave */ \
|
|
while (__builtin_expect(__pl_r, 0)) \
|
|
__pl_r = pl_deref_long(__lk_r) - (PLOCK64_WL_1|PLOCK64_SL_1|PLOCK64_RL_1); \
|
|
/* now return with __pl_r = 0 */ \
|
|
break; \
|
|
} \
|
|
!__pl_r; /* return value */ \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int *__lk_r = (unsigned int *)(lock); \
|
|
register unsigned int __set_r = PLOCK32_WL_1 | PLOCK32_SL_1; \
|
|
register unsigned int __msk_r = PLOCK32_WL_ANY | PLOCK32_SL_ANY; \
|
|
register unsigned int __pl_r; \
|
|
pl_barrier(); \
|
|
while (1) { \
|
|
__pl_r = pl_ldadd_acq(__lk_r, __set_r); \
|
|
if (__builtin_expect(__pl_r & __msk_r, 0)) { \
|
|
if (pl_ldadd_lax(__lk_r, - __set_r)) \
|
|
break; /* the caller needs to drop the lock now */ \
|
|
continue; /* lock was released, try again */ \
|
|
} \
|
|
/* ok we're the only writer, wait for readers to leave */ \
|
|
while (__builtin_expect(__pl_r, 0)) \
|
|
__pl_r = pl_deref_int(__lk_r) - (PLOCK32_WL_1|PLOCK32_SL_1|PLOCK32_RL_1); \
|
|
/* now return with __pl_r = 0 */ \
|
|
break; \
|
|
} \
|
|
!__pl_r; /* return value */ \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_try_rtow__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_try_rtow__(__FILE__,__LINE__); \
|
|
0; \
|
|
}) \
|
|
)
|
|
|
|
|
|
/* request atomic write access (A), return non-zero on success, otherwise 0.
|
|
* It's a bit tricky as we only use the W bits for this and want to distinguish
|
|
* between other atomic users and regular lock users. We have to give up if an
|
|
* S lock appears. It's possible that such a lock stays hidden in the W bits
|
|
* after an overflow, but in this case R is still held, ensuring we stay in the
|
|
* loop until we discover the conflict. The lock only return successfully if all
|
|
* readers are gone (or converted to A).
|
|
*/
|
|
#define pl_try_a(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long __pl_r = pl_deref_long(lock) & PLOCK64_SL_ANY; \
|
|
pl_barrier(); \
|
|
if (!__builtin_expect(__pl_r, 0)) { \
|
|
__pl_r = pl_ldadd_acq((lock), PLOCK64_WL_1); \
|
|
while (1) { \
|
|
if (__builtin_expect(__pl_r & PLOCK64_SL_ANY, 0)) { \
|
|
pl_sub_noret_lax((lock), PLOCK64_WL_1); \
|
|
break; /* return !__pl_r */ \
|
|
} \
|
|
__pl_r &= PLOCK64_RL_ANY; \
|
|
if (!__builtin_expect(__pl_r, 0)) \
|
|
break; /* return !__pl_r */ \
|
|
__pl_r = pl_deref_long(lock); \
|
|
} \
|
|
} \
|
|
!__pl_r; /* return value */ \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int __pl_r = pl_deref_int(lock) & PLOCK32_SL_ANY; \
|
|
pl_barrier(); \
|
|
if (!__builtin_expect(__pl_r, 0)) { \
|
|
__pl_r = pl_ldadd_acq((lock), PLOCK32_WL_1); \
|
|
while (1) { \
|
|
if (__builtin_expect(__pl_r & PLOCK32_SL_ANY, 0)) { \
|
|
pl_sub_noret_lax((lock), PLOCK32_WL_1); \
|
|
break; /* return !__pl_r */ \
|
|
} \
|
|
__pl_r &= PLOCK32_RL_ANY; \
|
|
if (!__builtin_expect(__pl_r, 0)) \
|
|
break; /* return !__pl_r */ \
|
|
__pl_r = pl_deref_int(lock); \
|
|
} \
|
|
} \
|
|
!__pl_r; /* return value */ \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_try_a__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_try_a__(__FILE__,__LINE__); \
|
|
0; \
|
|
}) \
|
|
)
|
|
|
|
/* request atomic write access (A) and wait for it. See comments in pl_try_a() for
|
|
* explanations.
|
|
*/
|
|
#define pl_take_a(lock) \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long *__lk_r = (unsigned long *)(lock); \
|
|
register unsigned long __set_r = PLOCK64_WL_1; \
|
|
register unsigned long __msk_r = PLOCK64_SL_ANY; \
|
|
register unsigned long __pl_r; \
|
|
__pl_r = pl_ldadd_acq(__lk_r, __set_r); \
|
|
while (__builtin_expect(__pl_r & PLOCK64_RL_ANY, 0)) { \
|
|
if (__builtin_expect(__pl_r & __msk_r, 0)) { \
|
|
pl_sub_noret_lax(__lk_r, __set_r); \
|
|
pl_wait_unlock_long(__lk_r, __msk_r); \
|
|
__pl_r = pl_ldadd_acq(__lk_r, __set_r); \
|
|
continue; \
|
|
} \
|
|
/* wait for all readers to leave or upgrade */ \
|
|
pl_cpu_relax(); pl_cpu_relax(); pl_cpu_relax(); \
|
|
__pl_r = pl_deref_long(lock); \
|
|
} \
|
|
pl_barrier(); \
|
|
0; \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int *__lk_r = (unsigned int *)(lock); \
|
|
register unsigned int __set_r = PLOCK32_WL_1; \
|
|
register unsigned int __msk_r = PLOCK32_SL_ANY; \
|
|
register unsigned int __pl_r; \
|
|
__pl_r = pl_ldadd_acq(__lk_r, __set_r); \
|
|
while (__builtin_expect(__pl_r & PLOCK32_RL_ANY, 0)) { \
|
|
if (__builtin_expect(__pl_r & __msk_r, 0)) { \
|
|
pl_sub_noret_lax(__lk_r, __set_r); \
|
|
pl_wait_unlock_int(__lk_r, __msk_r); \
|
|
__pl_r = pl_ldadd_acq(__lk_r, __set_r); \
|
|
continue; \
|
|
} \
|
|
/* wait for all readers to leave or upgrade */ \
|
|
pl_cpu_relax(); pl_cpu_relax(); pl_cpu_relax(); \
|
|
__pl_r = pl_deref_int(lock); \
|
|
} \
|
|
pl_barrier(); \
|
|
0; \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_take_a__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_take_a__(__FILE__,__LINE__); \
|
|
0; \
|
|
})
|
|
|
|
/* release atomic write access (A) lock */
|
|
#define pl_drop_a(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret_rel(lock, PLOCK64_WL_1); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret_rel(lock, PLOCK32_WL_1); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_drop_a__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_drop_a__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* Downgrade A to R. Inc(R), dec(W) then wait for W==0 */
|
|
#define pl_ator(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long *__lk_r = (unsigned long *)(lock); \
|
|
register unsigned long __set_r = PLOCK64_RL_1 - PLOCK64_WL_1; \
|
|
register unsigned long __msk_r = PLOCK64_WL_ANY; \
|
|
register unsigned long __pl_r = pl_ldadd(__lk_r, __set_r) + __set_r; \
|
|
while (__builtin_expect(__pl_r & __msk_r, 0)) { \
|
|
__pl_r = pl_wait_unlock_long(__lk_r, __msk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int *__lk_r = (unsigned int *)(lock); \
|
|
register unsigned int __set_r = PLOCK32_RL_1 - PLOCK32_WL_1; \
|
|
register unsigned int __msk_r = PLOCK32_WL_ANY; \
|
|
register unsigned int __pl_r = pl_ldadd(__lk_r, __set_r) + __set_r; \
|
|
while (__builtin_expect(__pl_r & __msk_r, 0)) { \
|
|
__pl_r = pl_wait_unlock_int(__lk_r, __msk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_ator__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_ator__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* Try to upgrade from R to A, return non-zero on success, otherwise 0.
|
|
* This lock will fail if S is held or appears while waiting (typically due to
|
|
* a previous grab that was disguised as a W due to an overflow). In case of
|
|
* failure to grab the lock, it MUST NOT be retried without first dropping R,
|
|
* or it may never complete due to S waiting for R to leave before upgrading
|
|
* to W. The lock succeeds once there's no more R (ie all of them have either
|
|
* completed or were turned to A).
|
|
*/
|
|
#define pl_try_rtoa(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long __pl_r = pl_deref_long(lock) & PLOCK64_SL_ANY; \
|
|
pl_barrier(); \
|
|
if (!__builtin_expect(__pl_r, 0)) { \
|
|
__pl_r = pl_ldadd_acq((lock), PLOCK64_WL_1 - PLOCK64_RL_1); \
|
|
while (1) { \
|
|
if (__builtin_expect(__pl_r & PLOCK64_SL_ANY, 0)) { \
|
|
pl_sub_noret_lax((lock), PLOCK64_WL_1 - PLOCK64_RL_1); \
|
|
break; /* return !__pl_r */ \
|
|
} \
|
|
__pl_r &= PLOCK64_RL_ANY; \
|
|
if (!__builtin_expect(__pl_r, 0)) \
|
|
break; /* return !__pl_r */ \
|
|
__pl_r = pl_deref_long(lock); \
|
|
} \
|
|
} \
|
|
!__pl_r; /* return value */ \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int __pl_r = pl_deref_int(lock) & PLOCK32_SL_ANY; \
|
|
pl_barrier(); \
|
|
if (!__builtin_expect(__pl_r, 0)) { \
|
|
__pl_r = pl_ldadd_acq((lock), PLOCK32_WL_1 - PLOCK32_RL_1); \
|
|
while (1) { \
|
|
if (__builtin_expect(__pl_r & PLOCK32_SL_ANY, 0)) { \
|
|
pl_sub_noret_lax((lock), PLOCK32_WL_1 - PLOCK32_RL_1); \
|
|
break; /* return !__pl_r */ \
|
|
} \
|
|
__pl_r &= PLOCK32_RL_ANY; \
|
|
if (!__builtin_expect(__pl_r, 0)) \
|
|
break; /* return !__pl_r */ \
|
|
__pl_r = pl_deref_int(lock); \
|
|
} \
|
|
} \
|
|
!__pl_r; /* return value */ \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_try_rtoa__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_try_rtoa__(__FILE__,__LINE__); \
|
|
0; \
|
|
}) \
|
|
)
|
|
|
|
|
|
/*
|
|
* The following operations cover the multiple writers model : U->R->J->C->A
|
|
*/
|
|
|
|
|
|
/* Upgrade R to J. Inc(W) then wait for R==W or S != 0 */
|
|
#define pl_rtoj(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long *__lk_r = (unsigned long *)(lock); \
|
|
register unsigned long __pl_r = pl_ldadd_acq(__lk_r, PLOCK64_WL_1) + PLOCK64_WL_1;\
|
|
register unsigned char __m = 0; \
|
|
while (!(__pl_r & PLOCK64_SL_ANY) && \
|
|
(__pl_r / PLOCK64_WL_1 != (__pl_r & PLOCK64_RL_ANY) / PLOCK64_RL_1)) { \
|
|
unsigned char __loops = __m + 1; \
|
|
__m = (__m << 1) + 1; \
|
|
do { \
|
|
pl_cpu_relax(); \
|
|
pl_cpu_relax(); \
|
|
} while (--__loops); \
|
|
__pl_r = pl_deref_long(__lk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int *__lk_r = (unsigned int *)(lock); \
|
|
register unsigned int __pl_r = pl_ldadd_acq(__lk_r, PLOCK32_WL_1) + PLOCK32_WL_1;\
|
|
register unsigned char __m = 0; \
|
|
while (!(__pl_r & PLOCK32_SL_ANY) && \
|
|
(__pl_r / PLOCK32_WL_1 != (__pl_r & PLOCK32_RL_ANY) / PLOCK32_RL_1)) { \
|
|
unsigned char __loops = __m + 1; \
|
|
__m = (__m << 1) + 1; \
|
|
do { \
|
|
pl_cpu_relax(); \
|
|
pl_cpu_relax(); \
|
|
} while (--__loops); \
|
|
__pl_r = pl_deref_int(__lk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_rtoj__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_rtoj__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* Upgrade J to C. Set S. Only one thread needs to do it though it's idempotent */
|
|
#define pl_jtoc(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long *__lk_r = (unsigned long *)(lock); \
|
|
register unsigned long __pl_r = pl_deref_long(__lk_r); \
|
|
if (!(__pl_r & PLOCK64_SL_ANY)) \
|
|
pl_or_noret(__lk_r, PLOCK64_SL_1); \
|
|
pl_barrier(); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int *__lk_r = (unsigned int *)(lock); \
|
|
register unsigned int __pl_r = pl_deref_int(__lk_r); \
|
|
if (!(__pl_r & PLOCK32_SL_ANY)) \
|
|
pl_or_noret(__lk_r, PLOCK32_SL_1); \
|
|
pl_barrier(); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_jtoc__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_jtoc__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* Upgrade R to C. Inc(W) then wait for R==W or S != 0 */
|
|
#define pl_rtoc(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long *__lk_r = (unsigned long *)(lock); \
|
|
register unsigned long __pl_r = pl_ldadd_acq(__lk_r, PLOCK64_WL_1) + PLOCK64_WL_1;\
|
|
register unsigned char __m = 0; \
|
|
while (__builtin_expect(!(__pl_r & PLOCK64_SL_ANY), 0)) { \
|
|
unsigned char __loops; \
|
|
if (__pl_r / PLOCK64_WL_1 == (__pl_r & PLOCK64_RL_ANY) / PLOCK64_RL_1) { \
|
|
pl_or_noret(__lk_r, PLOCK64_SL_1); \
|
|
break; \
|
|
} \
|
|
__loops = __m + 1; \
|
|
__m = (__m << 1) + 1; \
|
|
do { \
|
|
pl_cpu_relax(); \
|
|
pl_cpu_relax(); \
|
|
} while (--__loops); \
|
|
__pl_r = pl_deref_long(__lk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int *__lk_r = (unsigned int *)(lock); \
|
|
register unsigned int __pl_r = pl_ldadd_acq(__lk_r, PLOCK32_WL_1) + PLOCK32_WL_1;\
|
|
register unsigned char __m = 0; \
|
|
while (__builtin_expect(!(__pl_r & PLOCK32_SL_ANY), 0)) { \
|
|
unsigned char __loops; \
|
|
if (__pl_r / PLOCK32_WL_1 == (__pl_r & PLOCK32_RL_ANY) / PLOCK32_RL_1) { \
|
|
pl_or_noret(__lk_r, PLOCK32_SL_1); \
|
|
break; \
|
|
} \
|
|
__loops = __m + 1; \
|
|
__m = (__m << 1) + 1; \
|
|
do { \
|
|
pl_cpu_relax(); \
|
|
pl_cpu_relax(); \
|
|
} while (--__loops); \
|
|
__pl_r = pl_deref_int(__lk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_rtoj__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_rtoj__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* Drop the claim (C) lock : R--,W-- then clear S if !R */
|
|
#define pl_drop_c(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long *__lk_r = (unsigned long *)(lock); \
|
|
register unsigned long __set_r = - PLOCK64_RL_1 - PLOCK64_WL_1; \
|
|
register unsigned long __pl_r = pl_ldadd(__lk_r, __set_r) + __set_r; \
|
|
if (!(__pl_r & PLOCK64_RL_ANY)) \
|
|
pl_and_noret(__lk_r, ~PLOCK64_SL_1); \
|
|
pl_barrier(); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int *__lk_r = (unsigned int *)(lock); \
|
|
register unsigned int __set_r = - PLOCK32_RL_1 - PLOCK32_WL_1; \
|
|
register unsigned int __pl_r = pl_ldadd(__lk_r, __set_r) + __set_r; \
|
|
if (!(__pl_r & PLOCK32_RL_ANY)) \
|
|
pl_and_noret(__lk_r, ~PLOCK32_SL_1); \
|
|
pl_barrier(); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_drop_c__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_drop_c__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* Upgrade C to A. R-- then wait for !S or clear S if !R */
|
|
#define pl_ctoa(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long *__lk_r = (unsigned long *)(lock); \
|
|
register unsigned long __pl_r = pl_ldadd(__lk_r, -PLOCK64_RL_1) - PLOCK64_RL_1;\
|
|
while (__pl_r & PLOCK64_SL_ANY) { \
|
|
if (!(__pl_r & PLOCK64_RL_ANY)) { \
|
|
pl_and_noret(__lk_r, ~PLOCK64_SL_1); \
|
|
break; \
|
|
} \
|
|
pl_cpu_relax(); \
|
|
pl_cpu_relax(); \
|
|
__pl_r = pl_deref_long(__lk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int *__lk_r = (unsigned int *)(lock); \
|
|
register unsigned int __pl_r = pl_ldadd(__lk_r, -PLOCK32_RL_1) - PLOCK32_RL_1; \
|
|
while (__pl_r & PLOCK32_SL_ANY) { \
|
|
if (!(__pl_r & PLOCK32_RL_ANY)) { \
|
|
pl_and_noret(__lk_r, ~PLOCK32_SL_1); \
|
|
break; \
|
|
} \
|
|
pl_cpu_relax(); \
|
|
pl_cpu_relax(); \
|
|
__pl_r = pl_deref_int(__lk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_ctoa__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_ctoa__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* downgrade the atomic write access lock (A) to join (J) */
|
|
#define pl_atoj(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
pl_barrier(); \
|
|
pl_add_noret(lock, PLOCK64_RL_1); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
pl_barrier(); \
|
|
pl_add_noret(lock, PLOCK32_RL_1); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_atoj__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_atoj__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/* Returns non-zero if the thread calling it is the last writer, otherwise zero. It is
|
|
* designed to be called before pl_drop_j(), pl_drop_c() or pl_drop_a() for operations
|
|
* which need to be called only once.
|
|
*/
|
|
#define pl_last_writer(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
!(pl_deref_long(lock) & PLOCK64_WL_2PL); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
!(pl_deref_int(lock) & PLOCK32_WL_2PL); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_last_j__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_last_j__(__FILE__,__LINE__); \
|
|
0; \
|
|
}) \
|
|
)
|
|
|
|
/* attempt to get an exclusive write access via the J lock and wait for it.
|
|
* Only one thread may succeed in this operation. It will not conflict with
|
|
* other users and will first wait for all writers to leave, then for all
|
|
* readers to leave before starting. This offers a solution to obtain an
|
|
* exclusive access to a shared resource in the R/J/C/A model. A concurrent
|
|
* take_a() will wait for this one to finish first. Using a CAS instead of XADD
|
|
* should make the operation converge slightly faster. Returns non-zero on
|
|
* success otherwise 0.
|
|
*/
|
|
#define pl_try_j(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
register unsigned long *__lk_r = (unsigned long *)(lock); \
|
|
register unsigned long __set_r = PLOCK64_WL_1 | PLOCK64_RL_1; \
|
|
register unsigned long __msk_r = PLOCK64_WL_ANY; \
|
|
register unsigned long __pl_r; \
|
|
register unsigned char __m; \
|
|
pl_wait_unlock_long(__lk_r, __msk_r); \
|
|
__pl_r = pl_ldadd_acq(__lk_r, __set_r) + __set_r; \
|
|
/* wait for all other readers to leave */ \
|
|
__m = 0; \
|
|
while (__builtin_expect(__pl_r & PLOCK64_RL_2PL, 0)) { \
|
|
unsigned char __loops; \
|
|
/* give up on other writers */ \
|
|
if (__builtin_expect(__pl_r & PLOCK64_WL_2PL, 0)) { \
|
|
pl_sub_noret_lax(__lk_r, __set_r); \
|
|
__pl_r = 0; /* failed to get the lock */ \
|
|
break; \
|
|
} \
|
|
__loops = __m + 1; \
|
|
__m = (__m << 1) + 1; \
|
|
do { \
|
|
pl_cpu_relax(); \
|
|
pl_cpu_relax(); \
|
|
} while (--__loops); \
|
|
__pl_r = pl_deref_long(__lk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
__pl_r; /* return value, cannot be null on success */ \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
register unsigned int *__lk_r = (unsigned int *)(lock); \
|
|
register unsigned int __set_r = PLOCK32_WL_1 | PLOCK32_RL_1; \
|
|
register unsigned int __msk_r = PLOCK32_WL_ANY; \
|
|
register unsigned int __pl_r; \
|
|
register unsigned char __m; \
|
|
pl_wait_unlock_int(__lk_r, __msk_r); \
|
|
__pl_r = pl_ldadd_acq(__lk_r, __set_r) + __set_r; \
|
|
/* wait for all other readers to leave */ \
|
|
__m = 0; \
|
|
while (__builtin_expect(__pl_r & PLOCK32_RL_2PL, 0)) { \
|
|
unsigned char __loops; \
|
|
/* but rollback on other writers */ \
|
|
if (__builtin_expect(__pl_r & PLOCK32_WL_2PL, 0)) { \
|
|
pl_sub_noret_lax(__lk_r, __set_r); \
|
|
__pl_r = 0; /* failed to get the lock */ \
|
|
break; \
|
|
} \
|
|
__loops = __m + 1; \
|
|
__m = (__m << 1) + 1; \
|
|
do { \
|
|
pl_cpu_relax(); \
|
|
pl_cpu_relax(); \
|
|
} while (--__loops); \
|
|
__pl_r = pl_deref_int(__lk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
__pl_r; /* return value, cannot be null on success */ \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_try_j__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_try_j__(__FILE__,__LINE__); \
|
|
0; \
|
|
}) \
|
|
)
|
|
|
|
/* request an exclusive write access via the J lock and wait for it. Only one
|
|
* thread may succeed in this operation. It will not conflict with other users
|
|
* and will first wait for all writers to leave, then for all readers to leave
|
|
* before starting. This offers a solution to obtain an exclusive access to a
|
|
* shared resource in the R/J/C/A model. A concurrent take_a() will wait for
|
|
* this one to finish first. Using a CAS instead of XADD should make the
|
|
* operation converge slightly faster.
|
|
*/
|
|
#define pl_take_j(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
__label__ __retry; \
|
|
register unsigned long *__lk_r = (unsigned long *)(lock); \
|
|
register unsigned long __set_r = PLOCK64_WL_1 | PLOCK64_RL_1; \
|
|
register unsigned long __msk_r = PLOCK64_WL_ANY; \
|
|
register unsigned long __pl_r; \
|
|
register unsigned char __m; \
|
|
__retry: \
|
|
pl_wait_unlock_long(__lk_r, __msk_r); \
|
|
__pl_r = pl_ldadd_acq(__lk_r, __set_r) + __set_r; \
|
|
/* wait for all other readers to leave */ \
|
|
__m = 0; \
|
|
while (__builtin_expect(__pl_r & PLOCK64_RL_2PL, 0)) { \
|
|
unsigned char __loops; \
|
|
/* but rollback on other writers */ \
|
|
if (__builtin_expect(__pl_r & PLOCK64_WL_2PL, 0)) { \
|
|
pl_sub_noret_lax(__lk_r, __set_r); \
|
|
goto __retry; \
|
|
} \
|
|
__loops = __m + 1; \
|
|
__m = (__m << 1) + 1; \
|
|
do { \
|
|
pl_cpu_relax(); \
|
|
pl_cpu_relax(); \
|
|
} while (--__loops); \
|
|
__pl_r = pl_deref_long(__lk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
0; \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
__label__ __retry; \
|
|
register unsigned int *__lk_r = (unsigned int *)(lock); \
|
|
register unsigned int __set_r = PLOCK32_WL_1 | PLOCK32_RL_1; \
|
|
register unsigned int __msk_r = PLOCK32_WL_ANY; \
|
|
register unsigned int __pl_r; \
|
|
register unsigned char __m; \
|
|
__retry: \
|
|
pl_wait_unlock_int(__lk_r, __msk_r); \
|
|
__pl_r = pl_ldadd_acq(__lk_r, __set_r) + __set_r; \
|
|
/* wait for all other readers to leave */ \
|
|
__m = 0; \
|
|
while (__builtin_expect(__pl_r & PLOCK32_RL_2PL, 0)) { \
|
|
unsigned char __loops; \
|
|
/* but rollback on other writers */ \
|
|
if (__builtin_expect(__pl_r & PLOCK32_WL_2PL, 0)) { \
|
|
pl_sub_noret_lax(__lk_r, __set_r); \
|
|
goto __retry; \
|
|
} \
|
|
__loops = __m + 1; \
|
|
__m = (__m << 1) + 1; \
|
|
do { \
|
|
pl_cpu_relax(); \
|
|
pl_cpu_relax(); \
|
|
} while (--__loops); \
|
|
__pl_r = pl_deref_int(__lk_r); \
|
|
} \
|
|
pl_barrier(); \
|
|
0; \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_take_j__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_take_j__(__FILE__,__LINE__); \
|
|
0; \
|
|
}) \
|
|
)
|
|
|
|
/* drop the join (J) lock entirely */
|
|
#define pl_drop_j(lock) ( \
|
|
(sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret_rel(lock, PLOCK64_WL_1 | PLOCK64_RL_1); \
|
|
}) : (sizeof(*(lock)) == 4) ? ({ \
|
|
pl_barrier(); \
|
|
pl_sub_noret_rel(lock, PLOCK32_WL_1 | PLOCK32_RL_1); \
|
|
}) : ({ \
|
|
void __unsupported_argument_size_for_pl_drop_j__(char *,int); \
|
|
if (sizeof(*(lock)) != 4 && (sizeof(long) != 8 || sizeof(*(lock)) != 8)) \
|
|
__unsupported_argument_size_for_pl_drop_j__(__FILE__,__LINE__); \
|
|
}) \
|
|
)
|
|
|
|
/*
|
|
* The part below is for Low Overhead R/W locks (LORW). These ones are not
|
|
* upgradable and not necessarily fair but they try to be fast when uncontended
|
|
* and to limit the cost and perturbation during contention. Writers always
|
|
* have precedence over readers to preserve latency as much as possible.
|
|
*
|
|
* The principle is to offer a fast no-contention path and a limited total
|
|
* number of writes for the contended path. Since R/W locks are expected to be
|
|
* used in situations where there is a benefit in separating reads from writes,
|
|
* it is expected that reads are common (typ >= 50%) and that there is often at
|
|
* least one reader (otherwise a spinlock wouldn't be a problem). As such, a
|
|
* reader will try to pass instantly, detect contention and immediately retract
|
|
* and wait in the queue in case there is contention. A writer will first also
|
|
* try to pass instantly, and if it fails due to pending readers, it will mark
|
|
* that it's waiting so that readers stop entering. This will leave the writer
|
|
* waiting as close as possible to the point of being granted access. New
|
|
* writers will also notice this previous contention and will wait outside.
|
|
* This means that a successful access for a reader or a writer requires a
|
|
* single CAS, and a contended attempt will require one failed CAS and one
|
|
* successful XADD for a reader, or an optional OR and a N+1 CAS for the
|
|
* writer.
|
|
*
|
|
* A counter of shared users indicates the number of active readers, while a
|
|
* (single-bit) counter of exclusive writers indicates whether the lock is
|
|
* currently held for writes. This distinction also permits to use a single
|
|
* function to release the lock if desired, since the exclusive bit indicates
|
|
* the state of the caller of unlock(). The WRQ bit is cleared during the
|
|
* unlock.
|
|
*
|
|
* Layout: (32/64 bit):
|
|
* 31 2 1 0
|
|
* +-----------+--------------+-----+-----+
|
|
* | | SHR | WRQ | EXC |
|
|
* +-----------+--------------+-----+-----+
|
|
*
|
|
* In order to minimize operations, the WRQ bit is held during EXC so that the
|
|
* write waiter that had to fight for EXC doesn't have to release WRQ during
|
|
* its operations, and will just drop it along with EXC upon unlock.
|
|
*
|
|
* This means the following costs:
|
|
* reader:
|
|
* success: 1 CAS
|
|
* failure: 1 CAS + 1 XADD
|
|
* unlock: 1 SUB
|
|
* writer:
|
|
* success: 1 RD + 1 CAS
|
|
* failure: 1 RD + 1 CAS + 0/1 OR + N CAS
|
|
* unlock: 1 AND
|
|
*/
|
|
|
|
#define PLOCK_LORW_EXC_BIT ((sizeof(long) == 8) ? 0 : 0)
|
|
#define PLOCK_LORW_EXC_SIZE ((sizeof(long) == 8) ? 1 : 1)
|
|
#define PLOCK_LORW_EXC_BASE (1UL << PLOCK_LORW_EXC_BIT)
|
|
#define PLOCK_LORW_EXC_MASK (((1UL << PLOCK_LORW_EXC_SIZE) - 1UL) << PLOCK_LORW_EXC_BIT)
|
|
|
|
#define PLOCK_LORW_WRQ_BIT ((sizeof(long) == 8) ? 1 : 1)
|
|
#define PLOCK_LORW_WRQ_SIZE ((sizeof(long) == 8) ? 1 : 1)
|
|
#define PLOCK_LORW_WRQ_BASE (1UL << PLOCK_LORW_WRQ_BIT)
|
|
#define PLOCK_LORW_WRQ_MASK (((1UL << PLOCK_LORW_WRQ_SIZE) - 1UL) << PLOCK_LORW_WRQ_BIT)
|
|
|
|
#define PLOCK_LORW_SHR_BIT ((sizeof(long) == 8) ? 2 : 2)
|
|
#define PLOCK_LORW_SHR_SIZE ((sizeof(long) == 8) ? 30 : 30)
|
|
#define PLOCK_LORW_SHR_BASE (1UL << PLOCK_LORW_SHR_BIT)
|
|
#define PLOCK_LORW_SHR_MASK (((1UL << PLOCK_LORW_SHR_SIZE) - 1UL) << PLOCK_LORW_SHR_BIT)
|
|
|
|
__attribute__((unused,always_inline,no_instrument_function))
|
|
static inline void pl_lorw_rdlock(unsigned long *lock)
|
|
{
|
|
unsigned long lk = 0;
|
|
|
|
/* First, assume we're alone and try to get the read lock (fast path).
|
|
* It often works because read locks are often used on low-contention
|
|
* structs.
|
|
*/
|
|
lk = pl_cmpxchg(lock, 0, PLOCK_LORW_SHR_BASE);
|
|
if (!lk)
|
|
return;
|
|
|
|
/* so we were not alone, make sure there's no writer waiting for the
|
|
* lock to be empty of visitors.
|
|
*/
|
|
if (lk & PLOCK_LORW_WRQ_MASK)
|
|
#if defined(PLOCK_LORW_INLINE_WAIT) && !defined(PLOCK_DISABLE_EBO)
|
|
lk = __pl_wait_unlock_long(lock, PLOCK_LORW_WRQ_MASK);
|
|
#else
|
|
lk = pl_wait_unlock_long(lock, PLOCK_LORW_WRQ_MASK);
|
|
#endif
|
|
|
|
/* count us as visitor among others */
|
|
lk = pl_ldadd_acq(lock, PLOCK_LORW_SHR_BASE);
|
|
|
|
/* wait for end of exclusive access if any */
|
|
if (lk & PLOCK_LORW_EXC_MASK)
|
|
#if defined(PLOCK_LORW_INLINE_WAIT) && !defined(PLOCK_DISABLE_EBO)
|
|
lk = __pl_wait_unlock_long(lock, PLOCK_LORW_EXC_MASK);
|
|
#else
|
|
lk = pl_wait_unlock_long(lock, PLOCK_LORW_EXC_MASK);
|
|
#endif
|
|
}
|
|
|
|
|
|
__attribute__((unused,always_inline,no_instrument_function))
|
|
static inline void pl_lorw_wrlock(unsigned long *lock)
|
|
{
|
|
unsigned long lk = 0;
|
|
unsigned long old = 0;
|
|
|
|
/* first, make sure another writer is not already blocked waiting for
|
|
* readers to leave. Note that tests have shown that it can be even
|
|
* faster to avoid the first check and to unconditionally wait.
|
|
*/
|
|
lk = pl_deref_long(lock);
|
|
if (__builtin_expect(lk & PLOCK_LORW_WRQ_MASK, 1))
|
|
#if defined(PLOCK_LORW_INLINE_WAIT) && !defined(PLOCK_DISABLE_EBO)
|
|
lk = __pl_wait_unlock_long(lock, PLOCK_LORW_WRQ_MASK);
|
|
#else
|
|
lk = pl_wait_unlock_long(lock, PLOCK_LORW_WRQ_MASK);
|
|
#endif
|
|
|
|
do {
|
|
/* let's check for the two sources of contention at once */
|
|
|
|
if (__builtin_expect(lk & (PLOCK_LORW_SHR_MASK | PLOCK_LORW_EXC_MASK), 1)) {
|
|
/* check if there are still readers coming. If so, close the door and
|
|
* wait for them to leave.
|
|
*/
|
|
if (lk & PLOCK_LORW_SHR_MASK) {
|
|
/* note below, an OR is significantly cheaper than BTS or XADD */
|
|
if (!(lk & PLOCK_LORW_WRQ_MASK))
|
|
pl_or_noret(lock, PLOCK_LORW_WRQ_BASE);
|
|
#if defined(PLOCK_LORW_INLINE_WAIT) && !defined(PLOCK_DISABLE_EBO)
|
|
lk = __pl_wait_unlock_long(lock, PLOCK_LORW_SHR_MASK);
|
|
#else
|
|
lk = pl_wait_unlock_long(lock, PLOCK_LORW_SHR_MASK);
|
|
#endif
|
|
}
|
|
|
|
/* And also wait for a previous writer to finish. */
|
|
if (lk & PLOCK_LORW_EXC_MASK)
|
|
#if defined(PLOCK_LORW_INLINE_WAIT) && !defined(PLOCK_DISABLE_EBO)
|
|
lk = __pl_wait_unlock_long(lock, PLOCK_LORW_EXC_MASK);
|
|
#else
|
|
lk = pl_wait_unlock_long(lock, PLOCK_LORW_EXC_MASK);
|
|
#endif
|
|
}
|
|
|
|
/* A fresh new reader may appear right now if there were none
|
|
* above and we didn't close the door.
|
|
*/
|
|
old = lk & ~PLOCK_LORW_SHR_MASK & ~PLOCK_LORW_EXC_MASK;
|
|
lk = pl_cmpxchg(lock, old, old | PLOCK_LORW_EXC_BASE);
|
|
} while (lk != old);
|
|
|
|
/* done, not waiting anymore, the WRQ bit if any, will be dropped by the
|
|
* unlock
|
|
*/
|
|
}
|
|
|
|
|
|
__attribute__((unused,always_inline,no_instrument_function))
|
|
static inline void pl_lorw_rdunlock(unsigned long *lock)
|
|
{
|
|
pl_sub_noret_rel(lock, PLOCK_LORW_SHR_BASE);
|
|
}
|
|
|
|
__attribute__((unused,always_inline,no_instrument_function))
|
|
static inline void pl_lorw_wrunlock(unsigned long *lock)
|
|
{
|
|
pl_and_noret_rel(lock, ~(PLOCK_LORW_WRQ_MASK | PLOCK_LORW_EXC_MASK));
|
|
}
|
|
|
|
__attribute__((unused,always_inline,no_instrument_function))
|
|
static inline void pl_lorw_unlock(unsigned long *lock)
|
|
{
|
|
if (pl_deref_long(lock) & PLOCK_LORW_EXC_MASK)
|
|
pl_lorw_wrunlock(lock);
|
|
else
|
|
pl_lorw_rdunlock(lock);
|
|
}
|
|
|
|
#endif /* PL_PLOCK_H */
|