/* 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" /* 64 bit */ #define PLOCK64_RL_1 0x0000000000000004ULL #define PLOCK64_RL_ANY 0x00000000FFFFFFFCULL #define PLOCK64_SL_1 0x0000000100000000ULL #define PLOCK64_SL_ANY 0x0000000300000000ULL #define PLOCK64_WL_1 0x0000000400000000ULL #define PLOCK64_WL_ANY 0xFFFFFFFC00000000ULL /* 32 bit */ #define PLOCK32_RL_1 0x00000004 #define PLOCK32_RL_ANY 0x0000FFFC #define PLOCK32_SL_1 0x00010000 #define PLOCK32_SL_ANY 0x00030000 #define PLOCK32_WL_1 0x00040000 #define PLOCK32_WL_ANY 0xFFFC0000 /* dereferences <*p> as unsigned long without causing aliasing issues */ #define pl_deref_long(p) ({ volatile unsigned long *__plock_l = (void *)(p); *__plock_l; }) /* dereferences <*p> as unsigned int without causing aliasing issues */ #define pl_deref_int(p) ({ volatile unsigned int *__plock_i = (void *)(p); *__plock_i; }) /* request shared read access (R), return non-zero on success, otherwise 0 */ #define pl_try_r(lock) ( \ (sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \ unsigned long ret = pl_deref_long(lock) & PLOCK64_WL_ANY; \ pl_barrier(); \ if (!__builtin_expect(ret, 0)) { \ ret = pl_xadd((lock), PLOCK64_RL_1) & PLOCK64_WL_ANY; \ if (__builtin_expect(ret, 0)) \ pl_sub((lock), PLOCK64_RL_1); \ } \ !ret; /* return value */ \ }) : (sizeof(*(lock)) == 4) ? ({ \ unsigned int ret = pl_deref_int(lock) & PLOCK32_WL_ANY; \ pl_barrier(); \ if (!__builtin_expect(ret, 0)) { \ ret = pl_xadd((lock), PLOCK32_RL_1) & PLOCK32_WL_ANY; \ if (__builtin_expect(ret, 0)) \ pl_sub((lock), PLOCK32_RL_1); \ } \ !ret; /* return value */ \ }) : ({ \ void __unsupported_argument_size_for_pl_try_r__(char *,int); \ __unsupported_argument_size_for_pl_try_r__(__FILE__,__LINE__); \ 0; \ }) \ ) /* request shared read access (R) and wait for it */ #define pl_take_r(lock) \ do { \ while (__builtin_expect(pl_try_r(lock), 1) == 0) \ pl_cpu_relax(); \ } while (0) /* release the read access (R) lock */ #define pl_drop_r(lock) ( \ (sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \ pl_sub(lock, PLOCK64_RL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_sub(lock, PLOCK32_RL_1); \ }) : ({ \ void __unsupported_argument_size_for_pl_drop_r__(char *,int); \ __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) ? ({ \ unsigned long ret = pl_deref_long(lock); \ pl_barrier(); \ if (!__builtin_expect(ret & (PLOCK64_WL_ANY | PLOCK64_SL_ANY), 0)) { \ ret = pl_xadd((lock), PLOCK64_SL_1 | PLOCK64_RL_1) & \ (PLOCK64_WL_ANY | PLOCK64_SL_ANY); \ if (__builtin_expect(ret, 0)) \ pl_sub((lock), PLOCK64_SL_1 | PLOCK64_RL_1); \ } \ !ret; /* return value */ \ }) : (sizeof(*(lock)) == 4) ? ({ \ unsigned int ret = pl_deref_int(lock); \ pl_barrier(); \ if (!__builtin_expect(ret & (PLOCK32_WL_ANY | PLOCK32_SL_ANY), 0)) { \ ret = pl_xadd((lock), PLOCK32_SL_1 | PLOCK32_RL_1) & \ (PLOCK32_WL_ANY | PLOCK32_SL_ANY); \ if (__builtin_expect(ret, 0)) \ pl_sub((lock), PLOCK32_SL_1 | PLOCK32_RL_1); \ } \ !ret; /* return value */ \ }) : ({ \ void __unsupported_argument_size_for_pl_try_s__(char *,int); \ __unsupported_argument_size_for_pl_try_s__(__FILE__,__LINE__); \ 0; \ }) \ ) /* request a seek access (S) and wait for it */ #define pl_take_s(lock) \ do { \ while (__builtin_expect(pl_try_s(lock), 0) == 0) \ pl_cpu_relax(); \ } while (0) /* release the seek access (S) lock */ #define pl_drop_s(lock) ( \ (sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \ pl_sub(lock, PLOCK64_SL_1 + PLOCK64_RL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_sub(lock, PLOCK32_SL_1 + PLOCK32_RL_1); \ }) : ({ \ void __unsupported_argument_size_for_pl_drop_s__(char *,int); \ __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_sub(lock, PLOCK64_SL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_sub(lock, PLOCK32_SL_1); \ }) : ({ \ void __unsupported_argument_size_for_pl_stor__(char *,int); \ __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) ? ({ \ unsigned long ret = pl_xadd((lock), PLOCK64_WL_1); \ pl_barrier(); \ while ((ret & PLOCK64_RL_ANY) != PLOCK64_RL_1) \ ret = pl_deref_long(lock); \ }) : (sizeof(*(lock)) == 4) ? ({ \ unsigned int ret = pl_xadd((lock), PLOCK32_WL_1); \ pl_barrier(); \ while ((ret & PLOCK32_RL_ANY) != PLOCK32_RL_1) \ ret = pl_deref_int(lock); \ }) : ({ \ void __unsupported_argument_size_for_pl_stow__(char *,int); \ __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_sub(lock, PLOCK64_WL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_sub(lock, PLOCK32_WL_1); \ }) : ({ \ void __unsupported_argument_size_for_pl_wtos__(char *,int); \ __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_sub(lock, PLOCK64_WL_1 | PLOCK64_SL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_sub(lock, PLOCK32_WL_1 | PLOCK32_SL_1); \ }) : ({ \ void __unsupported_argument_size_for_pl_wtor__(char *,int); \ __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) ? ({ \ unsigned long ret = pl_deref_long(lock); \ pl_barrier(); \ if (!__builtin_expect(ret & (PLOCK64_WL_ANY | PLOCK64_SL_ANY), 0)) { \ ret = pl_xadd((lock), PLOCK64_WL_1 | PLOCK64_SL_1 | PLOCK64_RL_1); \ if (__builtin_expect(ret & (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); \ ret &= (PLOCK64_WL_ANY | PLOCK64_SL_ANY); /* return value */ \ } else { \ /* wait for all other readers to leave */ \ while (ret) \ ret = pl_deref_long(lock) - \ (PLOCK64_WL_1 | PLOCK64_SL_1 | PLOCK64_RL_1); \ ret = 0; \ } \ } \ !ret; /* return value */ \ }) : (sizeof(*(lock)) == 4) ? ({ \ unsigned int ret = pl_deref_int(lock); \ pl_barrier(); \ if (!__builtin_expect(ret & (PLOCK32_WL_ANY | PLOCK32_SL_ANY), 0)) { \ ret = pl_xadd((lock), PLOCK32_WL_1 | PLOCK32_SL_1 | PLOCK32_RL_1); \ if (__builtin_expect(ret & (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); \ ret &= (PLOCK32_WL_ANY | PLOCK32_SL_ANY); /* return value */ \ } else { \ /* wait for all other readers to leave */ \ while (ret) \ ret = pl_deref_int(lock) - \ (PLOCK32_WL_1 | PLOCK32_SL_1 | PLOCK32_RL_1); \ ret = 0; \ } \ } \ !ret; /* return value */ \ }) : ({ \ void __unsupported_argument_size_for_pl_try_w__(char *,int); \ __unsupported_argument_size_for_pl_try_w__(__FILE__,__LINE__); \ 0; \ }) \ ) /* request a seek access (W) and wait for it */ #define pl_take_w(lock) \ do { \ while (__builtin_expect(pl_try_w(lock), 0) == 0) \ pl_cpu_relax(); \ } while (0) /* drop the write (W) lock entirely */ #define pl_drop_w(lock) ( \ (sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \ pl_sub(lock, PLOCK64_WL_1 | PLOCK64_SL_1 | PLOCK64_RL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_sub(lock, PLOCK32_WL_1 | PLOCK32_SL_1 | PLOCK32_RL_1); \ }) : ({ \ void __unsupported_argument_size_for_pl_drop_w__(char *,int); \ __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) ? ({ \ unsigned long ret = pl_deref_long(lock); \ pl_barrier(); \ if (!__builtin_expect(ret & (PLOCK64_WL_ANY | PLOCK64_SL_ANY), 0)) { \ ret = pl_xadd((lock), PLOCK64_SL_1) & \ (PLOCK64_WL_ANY | PLOCK64_SL_ANY); \ if (__builtin_expect(ret, 0)) \ pl_sub((lock), PLOCK64_SL_1); \ } \ !ret; /* return value */ \ }) : (sizeof(*(lock)) == 4) ? ({ \ unsigned int ret = pl_deref_int(lock); \ pl_barrier(); \ if (!__builtin_expect(ret & (PLOCK32_WL_ANY | PLOCK32_SL_ANY), 0)) { \ ret = pl_xadd((lock), PLOCK32_SL_1) & \ (PLOCK32_WL_ANY | PLOCK32_SL_ANY); \ if (__builtin_expect(ret, 0)) \ pl_sub((lock), PLOCK32_SL_1); \ } \ !ret; /* return value */ \ }) : ({ \ void __unsupported_argument_size_for_pl_try_rtos__(char *,int); \ __unsupported_argument_size_for_pl_try_rtos__(__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) ? ({ \ unsigned long ret = pl_deref_long(lock) & PLOCK64_SL_ANY; \ pl_barrier(); \ if (!__builtin_expect(ret, 0)) { \ ret = pl_xadd((lock), PLOCK64_WL_1); \ while (1) { \ if (__builtin_expect(ret & PLOCK64_SL_ANY, 0)) { \ pl_sub((lock), PLOCK64_WL_1); \ break; /* return !ret */ \ } \ ret &= PLOCK64_RL_ANY; \ if (!__builtin_expect(ret, 0)) \ break; /* return !ret */ \ ret = pl_deref_long(lock); \ } \ } \ !ret; /* return value */ \ }) : (sizeof(*(lock)) == 4) ? ({ \ unsigned int ret = pl_deref_int(lock) & PLOCK32_SL_ANY; \ pl_barrier(); \ if (!__builtin_expect(ret, 0)) { \ ret = pl_xadd((lock), PLOCK32_WL_1); \ while (1) { \ if (__builtin_expect(ret & PLOCK32_SL_ANY, 0)) { \ pl_sub((lock), PLOCK32_WL_1); \ break; /* return !ret */ \ } \ ret &= PLOCK32_RL_ANY; \ if (!__builtin_expect(ret, 0)) \ break; /* return !ret */ \ ret = pl_deref_int(lock); \ } \ } \ !ret; /* return value */ \ }) : ({ \ void __unsupported_argument_size_for_pl_try_a__(char *,int); \ __unsupported_argument_size_for_pl_try_a__(__FILE__,__LINE__); \ 0; \ }) \ ) /* request atomic write access (A) and wait for it */ #define pl_take_a(lock) \ do { \ while (__builtin_expect(pl_try_a(lock), 1) == 0) \ pl_cpu_relax(); \ } while (0) /* release atomic write access (A) lock */ #define pl_drop_a(lock) ( \ (sizeof(long) == 8 && sizeof(*(lock)) == 8) ? ({ \ pl_sub(lock, PLOCK64_WL_1); \ }) : (sizeof(*(lock)) == 4) ? ({ \ pl_sub(lock, PLOCK32_WL_1); \ }) : ({ \ void __unsupported_argument_size_for_pl_drop_a__(char *,int); \ __unsupported_argument_size_for_pl_drop_a__(__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) ? ({ \ unsigned long ret = pl_deref_long(lock) & PLOCK64_SL_ANY; \ pl_barrier(); \ if (!__builtin_expect(ret, 0)) { \ ret = pl_xadd((lock), PLOCK64_WL_1 - PLOCK64_RL_1); \ while (1) { \ if (__builtin_expect(ret & PLOCK64_SL_ANY, 0)) { \ pl_sub((lock), PLOCK64_WL_1 - PLOCK64_RL_1); \ break; /* return !ret */ \ } \ ret &= PLOCK64_RL_ANY; \ if (!__builtin_expect(ret, 0)) \ break; /* return !ret */ \ ret = pl_deref_long(lock); \ } \ } \ !ret; /* return value */ \ }) : (sizeof(*(lock)) == 4) ? ({ \ unsigned int ret = pl_deref_int(lock) & PLOCK32_SL_ANY; \ pl_barrier(); \ if (!__builtin_expect(ret, 0)) { \ ret = pl_xadd((lock), PLOCK32_WL_1 - PLOCK32_RL_1); \ while (1) { \ if (__builtin_expect(ret & PLOCK32_SL_ANY, 0)) { \ pl_sub((lock), PLOCK32_WL_1 - PLOCK32_RL_1); \ break; /* return !ret */ \ } \ ret &= PLOCK32_RL_ANY; \ if (!__builtin_expect(ret, 0)) \ break; /* return !ret */ \ ret = pl_deref_int(lock); \ } \ } \ !ret; /* return value */ \ }) : ({ \ void __unsupported_argument_size_for_pl_try_rtoa__(char *,int); \ __unsupported_argument_size_for_pl_try_rtoa__(__FILE__,__LINE__); \ 0; \ }) \ )