/* plock - progressive locks * * Copyright (C) 2012-2017 Willy Tarreau * * 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. */ #include "atomic-ops.h" #ifdef _POSIX_PRIORITY_SCHEDULING #include #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 to release all bits covered by , 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 __attribute__((unused,noinline,no_instrument_function)) 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 >= 200; loops -= 10) pl_cpu_relax(); for (; loops >= 1; loops--) pl_barrier(); ret = pl_deref_long(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; } #endif /* PLOCK_DISABLE_EBO */ /* This function waits for to release all bits covered by , 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,noinline,no_instrument_function)) 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; } #endif /* PLOCK_DISABLE_EBO */ /* This function waits for to change from value 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 to change from value 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_xadd((lock), PLOCK64_RL_1) & PLOCK64_WL_ANY; \ if (__builtin_expect(__pl_r, 0)) \ pl_sub((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_xadd((lock), PLOCK32_RL_1) & PLOCK32_WL_ANY; \ if (__builtin_expect(__pl_r, 0)) \ pl_sub((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; \ while (1) { \ if (__builtin_expect(pl_deref_long(__lk_r) & __msk_r, 0)) \ pl_wait_unlock_long(__lk_r, __msk_r); \ if (!__builtin_expect(pl_xadd(__lk_r, __set_r) & __msk_r, 0)) \ break; \ pl_sub(__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; \ while (1) { \ if (__builtin_expect(pl_deref_int(__lk_r) & __msk_r, 0)) \ pl_wait_unlock_int(__lk_r, __msk_r); \ if (!__builtin_expect(pl_xadd(__lk_r, __set_r) & __msk_r, 0)) \ break; \ pl_sub(__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(lock, PLOCK64_RL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_barrier(); \ pl_sub(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_xadd((lock), PLOCK64_SL_1 | PLOCK64_RL_1) & \ (PLOCK64_WL_ANY | PLOCK64_SL_ANY); \ if (__builtin_expect(__pl_r, 0)) \ pl_sub((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_xadd((lock), PLOCK32_SL_1 | PLOCK32_RL_1) & \ (PLOCK32_WL_ANY | PLOCK32_SL_ANY); \ if (__builtin_expect(__pl_r, 0)) \ pl_sub((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_xadd(__lk_r, __set_r) & __msk_r, 0)) \ break; \ pl_sub(__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_xadd(__lk_r, __set_r) & __msk_r, 0)) \ break; \ pl_sub(__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(lock, PLOCK64_SL_1 + PLOCK64_RL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_barrier(); \ pl_sub(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(lock, PLOCK64_SL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_barrier(); \ pl_sub(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_xadd((lock), PLOCK64_WL_1); \ while ((__pl_r & PLOCK64_RL_ANY) != PLOCK64_RL_1) \ __pl_r = pl_deref_long(lock); \ pl_barrier(); \ }) : (sizeof(*(lock)) == 4) ? ({ \ register unsigned int __pl_r = pl_xadd((lock), PLOCK32_WL_1); \ while ((__pl_r & PLOCK32_RL_ANY) != PLOCK32_RL_1) \ __pl_r = pl_deref_int(lock); \ 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(lock, PLOCK64_WL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_barrier(); \ pl_sub(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(lock, PLOCK64_WL_1 | PLOCK64_SL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_barrier(); \ pl_sub(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_xadd((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((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_xadd((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((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_xadd(__lk_r, __set_r); \ if (!__builtin_expect(__pl_r & __msk_r, 0)) \ break; \ pl_sub(__lk_r, __set_r); \ __pl_r = pl_wait_unlock_long(__lk_r, __msk_r); \ } \ /* wait for all other readers to leave */ \ while (__builtin_expect(__pl_r, 0)) \ __pl_r = pl_deref_long(__lk_r) - __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_xadd(__lk_r, __set_r); \ if (!__builtin_expect(__pl_r & __msk_r, 0)) \ break; \ pl_sub(__lk_r, __set_r); \ __pl_r = pl_wait_unlock_int(__lk_r, __msk_r); \ } \ /* wait for all other readers to leave */ \ while (__builtin_expect(__pl_r, 0)) \ __pl_r = pl_deref_int(__lk_r) - __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(lock, PLOCK64_WL_1 | PLOCK64_SL_1 | PLOCK64_RL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_barrier(); \ pl_sub(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_deref_long(lock); \ pl_barrier(); \ if (!__builtin_expect(__pl_r & (PLOCK64_WL_ANY | PLOCK64_SL_ANY), 0)) { \ __pl_r = pl_xadd((lock), PLOCK64_SL_1) & \ (PLOCK64_WL_ANY | PLOCK64_SL_ANY); \ if (__builtin_expect(__pl_r, 0)) \ pl_sub((lock), PLOCK64_SL_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_xadd((lock), PLOCK32_SL_1) & \ (PLOCK32_WL_ANY | PLOCK32_SL_ANY); \ if (__builtin_expect(__pl_r, 0)) \ pl_sub((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_xadd(__lk_r, __set_r); \ if (__builtin_expect(__pl_r & __msk_r, 0)) { \ if (pl_xadd(__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_xadd(__lk_r, __set_r); \ if (__builtin_expect(__pl_r & __msk_r, 0)) { \ if (pl_xadd(__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_xadd((lock), PLOCK64_WL_1); \ while (1) { \ if (__builtin_expect(__pl_r & PLOCK64_SL_ANY, 0)) { \ pl_sub((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_xadd((lock), PLOCK32_WL_1); \ while (1) { \ if (__builtin_expect(__pl_r & PLOCK32_SL_ANY, 0)) { \ pl_sub((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_xadd(__lk_r, __set_r); \ while (__builtin_expect(__pl_r & PLOCK64_RL_ANY, 0)) { \ if (__builtin_expect(__pl_r & __msk_r, 0)) { \ pl_sub(__lk_r, __set_r); \ pl_wait_unlock_long(__lk_r, __msk_r); \ __pl_r = pl_xadd(__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_xadd(__lk_r, __set_r); \ while (__builtin_expect(__pl_r & PLOCK32_RL_ANY, 0)) { \ if (__builtin_expect(__pl_r & __msk_r, 0)) { \ pl_sub(__lk_r, __set_r); \ pl_wait_unlock_int(__lk_r, __msk_r); \ __pl_r = pl_xadd(__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(lock, PLOCK64_WL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_barrier(); \ pl_sub(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_xadd(__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_xadd(__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_xadd((lock), PLOCK64_WL_1 - PLOCK64_RL_1); \ while (1) { \ if (__builtin_expect(__pl_r & PLOCK64_SL_ANY, 0)) { \ pl_sub((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_xadd((lock), PLOCK32_WL_1 - PLOCK32_RL_1); \ while (1) { \ if (__builtin_expect(__pl_r & PLOCK32_SL_ANY, 0)) { \ pl_sub((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_xadd(__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_xadd(__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(__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(__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_xadd(__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(__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_xadd(__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(__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_xadd(__lk_r, __set_r) + __set_r; \ if (!(__pl_r & PLOCK64_RL_ANY)) \ pl_and(__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_xadd(__lk_r, __set_r) + __set_r; \ if (!(__pl_r & PLOCK32_RL_ANY)) \ pl_and(__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_xadd(__lk_r, -PLOCK64_RL_1) - PLOCK64_RL_1; \ while (__pl_r & PLOCK64_SL_ANY) { \ if (!(__pl_r & PLOCK64_RL_ANY)) { \ pl_and(__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_xadd(__lk_r, -PLOCK32_RL_1) - PLOCK32_RL_1; \ while (__pl_r & PLOCK32_SL_ANY) { \ if (!(__pl_r & PLOCK32_RL_ANY)) { \ pl_and(__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(lock, PLOCK64_RL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_barrier(); \ pl_add(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_xadd(__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(__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_xadd(__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(__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_xadd(__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(__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_xadd(__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(__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(lock, PLOCK64_WL_1 | PLOCK64_RL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_barrier(); \ pl_sub(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) lk = pl_wait_unlock_long(lock, PLOCK_LORW_WRQ_MASK); /* count us as visitor among others */ lk = pl_xadd(lock, PLOCK_LORW_SHR_BASE); /* wait for end of exclusive access if any */ if (lk & PLOCK_LORW_EXC_MASK) lk = pl_wait_unlock_long(lock, PLOCK_LORW_EXC_MASK); } __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)) lk = pl_wait_unlock_long(lock, PLOCK_LORW_WRQ_MASK); 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(lock, PLOCK_LORW_WRQ_BASE); lk = pl_wait_unlock_long(lock, PLOCK_LORW_SHR_MASK); } /* And also wait for a previous writer to finish. */ if (lk & PLOCK_LORW_EXC_MASK) lk = pl_wait_unlock_long(lock, PLOCK_LORW_EXC_MASK); } /* 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(lock, PLOCK_LORW_SHR_BASE); } __attribute__((unused,always_inline,no_instrument_function)) static inline void pl_lorw_wrunlock(unsigned long *lock) { pl_and(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); }