Greg Kroah-Hartman | b244131 | 2017-11-01 15:07:57 +0100 | [diff] [blame] | 1 | // SPDX-License-Identifier: GPL-2.0 |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 2 | /* |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 3 | * Out of line spinlock code. |
| 4 | * |
Heiko Carstens | a53c8fa | 2012-07-20 11:15:04 +0200 | [diff] [blame] | 5 | * Copyright IBM Corp. 2004, 2006 |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 6 | * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com) |
| 7 | */ |
| 8 | |
| 9 | #include <linux/types.h> |
Paul Gortmaker | d321796 | 2017-02-09 15:20:25 -0500 | [diff] [blame] | 10 | #include <linux/export.h> |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 11 | #include <linux/spinlock.h> |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 12 | #include <linux/jiffies.h> |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 13 | #include <linux/init.h> |
Martin Schwidefsky | 8b646bd | 2012-03-11 11:59:26 -0400 | [diff] [blame] | 14 | #include <linux/smp.h> |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 15 | #include <linux/percpu.h> |
Heiko Carstens | b378a98 | 2023-06-22 10:46:32 +0200 | [diff] [blame] | 16 | #include <linux/io.h> |
Vasily Gorbik | f554be4 | 2017-10-12 13:01:47 +0200 | [diff] [blame] | 17 | #include <asm/alternative.h> |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 18 | |
Martin Schwidefsky | 2c72a44 | 2015-01-14 17:52:33 +0100 | [diff] [blame] | 19 | int spin_retry = -1; |
| 20 | |
| 21 | static int __init spin_retry_init(void) |
| 22 | { |
| 23 | if (spin_retry < 0) |
Martin Schwidefsky | b13de4b | 2017-03-24 17:00:45 +0100 | [diff] [blame] | 24 | spin_retry = 1000; |
Martin Schwidefsky | 2c72a44 | 2015-01-14 17:52:33 +0100 | [diff] [blame] | 25 | return 0; |
| 26 | } |
| 27 | early_initcall(spin_retry_init); |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 28 | |
Heiko Carstens | 74e74f9 | 2021-10-21 15:14:43 +0200 | [diff] [blame] | 29 | /* |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 30 | * spin_retry= parameter |
| 31 | */ |
| 32 | static int __init spin_retry_setup(char *str) |
| 33 | { |
| 34 | spin_retry = simple_strtoul(str, &str, 0); |
| 35 | return 1; |
| 36 | } |
| 37 | __setup("spin_retry=", spin_retry_setup); |
| 38 | |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 39 | struct spin_wait { |
| 40 | struct spin_wait *next, *prev; |
| 41 | int node_id; |
| 42 | } __aligned(32); |
| 43 | |
| 44 | static DEFINE_PER_CPU_ALIGNED(struct spin_wait, spin_wait[4]); |
| 45 | |
| 46 | #define _Q_LOCK_CPU_OFFSET 0 |
| 47 | #define _Q_LOCK_STEAL_OFFSET 16 |
| 48 | #define _Q_TAIL_IDX_OFFSET 18 |
| 49 | #define _Q_TAIL_CPU_OFFSET 20 |
| 50 | |
| 51 | #define _Q_LOCK_CPU_MASK 0x0000ffff |
| 52 | #define _Q_LOCK_STEAL_ADD 0x00010000 |
| 53 | #define _Q_LOCK_STEAL_MASK 0x00030000 |
| 54 | #define _Q_TAIL_IDX_MASK 0x000c0000 |
| 55 | #define _Q_TAIL_CPU_MASK 0xfff00000 |
| 56 | |
| 57 | #define _Q_LOCK_MASK (_Q_LOCK_CPU_MASK | _Q_LOCK_STEAL_MASK) |
| 58 | #define _Q_TAIL_MASK (_Q_TAIL_IDX_MASK | _Q_TAIL_CPU_MASK) |
| 59 | |
| 60 | void arch_spin_lock_setup(int cpu) |
| 61 | { |
| 62 | struct spin_wait *node; |
| 63 | int ix; |
| 64 | |
| 65 | node = per_cpu_ptr(&spin_wait[0], cpu); |
| 66 | for (ix = 0; ix < 4; ix++, node++) { |
| 67 | memset(node, 0, sizeof(*node)); |
| 68 | node->node_id = ((cpu + 1) << _Q_TAIL_CPU_OFFSET) + |
| 69 | (ix << _Q_TAIL_IDX_OFFSET); |
| 70 | } |
| 71 | } |
| 72 | |
Martin Schwidefsky | 7f7e6e2 | 2017-04-19 14:54:05 +0200 | [diff] [blame] | 73 | static inline int arch_load_niai4(int *lock) |
| 74 | { |
| 75 | int owner; |
| 76 | |
Heiko Carstens | cceb018 | 2019-10-18 13:23:16 +0200 | [diff] [blame] | 77 | asm_inline volatile( |
Heiko Carstens | fad442d | 2022-05-11 14:05:25 +0200 | [diff] [blame] | 78 | ALTERNATIVE("nop", ".insn rre,0xb2fa0000,4,0", 49) /* NIAI 4 */ |
Martin Schwidefsky | 7f7e6e2 | 2017-04-19 14:54:05 +0200 | [diff] [blame] | 79 | " l %0,%1\n" |
| 80 | : "=d" (owner) : "Q" (*lock) : "memory"); |
Heiko Carstens | 78ca4fe | 2017-11-14 13:47:00 +0100 | [diff] [blame] | 81 | return owner; |
Martin Schwidefsky | 7f7e6e2 | 2017-04-19 14:54:05 +0200 | [diff] [blame] | 82 | } |
| 83 | |
| 84 | static inline int arch_cmpxchg_niai8(int *lock, int old, int new) |
| 85 | { |
| 86 | int expected = old; |
| 87 | |
Heiko Carstens | cceb018 | 2019-10-18 13:23:16 +0200 | [diff] [blame] | 88 | asm_inline volatile( |
Heiko Carstens | fad442d | 2022-05-11 14:05:25 +0200 | [diff] [blame] | 89 | ALTERNATIVE("nop", ".insn rre,0xb2fa0000,8,0", 49) /* NIAI 8 */ |
Martin Schwidefsky | 7f7e6e2 | 2017-04-19 14:54:05 +0200 | [diff] [blame] | 90 | " cs %0,%3,%1\n" |
| 91 | : "=d" (old), "=Q" (*lock) |
| 92 | : "0" (old), "d" (new), "Q" (*lock) |
| 93 | : "cc", "memory"); |
| 94 | return expected == old; |
| 95 | } |
| 96 | |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 97 | static inline struct spin_wait *arch_spin_decode_tail(int lock) |
| 98 | { |
| 99 | int ix, cpu; |
| 100 | |
| 101 | ix = (lock & _Q_TAIL_IDX_MASK) >> _Q_TAIL_IDX_OFFSET; |
| 102 | cpu = (lock & _Q_TAIL_CPU_MASK) >> _Q_TAIL_CPU_OFFSET; |
| 103 | return per_cpu_ptr(&spin_wait[ix], cpu - 1); |
| 104 | } |
| 105 | |
| 106 | static inline int arch_spin_yield_target(int lock, struct spin_wait *node) |
| 107 | { |
| 108 | if (lock & _Q_LOCK_CPU_MASK) |
| 109 | return lock & _Q_LOCK_CPU_MASK; |
| 110 | if (node == NULL || node->prev == NULL) |
| 111 | return 0; /* 0 -> no target cpu */ |
| 112 | while (node->prev) |
| 113 | node = node->prev; |
| 114 | return node->node_id >> _Q_TAIL_CPU_OFFSET; |
| 115 | } |
| 116 | |
| 117 | static inline void arch_spin_lock_queued(arch_spinlock_t *lp) |
| 118 | { |
| 119 | struct spin_wait *node, *next; |
| 120 | int lockval, ix, node_id, tail_id, old, new, owner, count; |
| 121 | |
| 122 | ix = S390_lowcore.spinlock_index++; |
| 123 | barrier(); |
| 124 | lockval = SPINLOCK_LOCKVAL; /* cpu + 1 */ |
| 125 | node = this_cpu_ptr(&spin_wait[ix]); |
| 126 | node->prev = node->next = NULL; |
| 127 | node_id = node->node_id; |
| 128 | |
| 129 | /* Enqueue the node for this CPU in the spinlock wait queue */ |
| 130 | while (1) { |
| 131 | old = READ_ONCE(lp->lock); |
| 132 | if ((old & _Q_LOCK_CPU_MASK) == 0 && |
| 133 | (old & _Q_LOCK_STEAL_MASK) != _Q_LOCK_STEAL_MASK) { |
| 134 | /* |
| 135 | * The lock is free but there may be waiters. |
| 136 | * With no waiters simply take the lock, if there |
| 137 | * are waiters try to steal the lock. The lock may |
| 138 | * be stolen three times before the next queued |
| 139 | * waiter will get the lock. |
| 140 | */ |
| 141 | new = (old ? (old + _Q_LOCK_STEAL_ADD) : 0) | lockval; |
| 142 | if (__atomic_cmpxchg_bool(&lp->lock, old, new)) |
| 143 | /* Got the lock */ |
| 144 | goto out; |
| 145 | /* lock passing in progress */ |
| 146 | continue; |
| 147 | } |
| 148 | /* Make the node of this CPU the new tail. */ |
| 149 | new = node_id | (old & _Q_LOCK_MASK); |
| 150 | if (__atomic_cmpxchg_bool(&lp->lock, old, new)) |
| 151 | break; |
| 152 | } |
| 153 | /* Set the 'next' pointer of the tail node in the queue */ |
| 154 | tail_id = old & _Q_TAIL_MASK; |
| 155 | if (tail_id != 0) { |
| 156 | node->prev = arch_spin_decode_tail(tail_id); |
| 157 | WRITE_ONCE(node->prev->next, node); |
| 158 | } |
| 159 | |
| 160 | /* Pass the virtual CPU to the lock holder if it is not running */ |
| 161 | owner = arch_spin_yield_target(old, node); |
| 162 | if (owner && arch_vcpu_is_preempted(owner - 1)) |
| 163 | smp_yield_cpu(owner - 1); |
| 164 | |
| 165 | /* Spin on the CPU local node->prev pointer */ |
| 166 | if (tail_id != 0) { |
| 167 | count = spin_retry; |
| 168 | while (READ_ONCE(node->prev) != NULL) { |
| 169 | if (count-- >= 0) |
| 170 | continue; |
| 171 | count = spin_retry; |
| 172 | /* Query running state of lock holder again. */ |
| 173 | owner = arch_spin_yield_target(old, node); |
| 174 | if (owner && arch_vcpu_is_preempted(owner - 1)) |
| 175 | smp_yield_cpu(owner - 1); |
| 176 | } |
| 177 | } |
| 178 | |
| 179 | /* Spin on the lock value in the spinlock_t */ |
| 180 | count = spin_retry; |
| 181 | while (1) { |
| 182 | old = READ_ONCE(lp->lock); |
| 183 | owner = old & _Q_LOCK_CPU_MASK; |
| 184 | if (!owner) { |
| 185 | tail_id = old & _Q_TAIL_MASK; |
| 186 | new = ((tail_id != node_id) ? tail_id : 0) | lockval; |
| 187 | if (__atomic_cmpxchg_bool(&lp->lock, old, new)) |
| 188 | /* Got the lock */ |
| 189 | break; |
| 190 | continue; |
| 191 | } |
| 192 | if (count-- >= 0) |
| 193 | continue; |
| 194 | count = spin_retry; |
| 195 | if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(owner - 1)) |
| 196 | smp_yield_cpu(owner - 1); |
| 197 | } |
| 198 | |
| 199 | /* Pass lock_spin job to next CPU in the queue */ |
| 200 | if (node_id && tail_id != node_id) { |
| 201 | /* Wait until the next CPU has set up the 'next' pointer */ |
| 202 | while ((next = READ_ONCE(node->next)) == NULL) |
| 203 | ; |
| 204 | next->prev = NULL; |
| 205 | } |
| 206 | |
| 207 | out: |
| 208 | S390_lowcore.spinlock_index--; |
| 209 | } |
| 210 | |
| 211 | static inline void arch_spin_lock_classic(arch_spinlock_t *lp) |
| 212 | { |
| 213 | int lockval, old, new, owner, count; |
| 214 | |
| 215 | lockval = SPINLOCK_LOCKVAL; /* cpu + 1 */ |
| 216 | |
| 217 | /* Pass the virtual CPU to the lock holder if it is not running */ |
Linus Torvalds | 8e9a2db | 2017-11-13 12:38:26 -0800 | [diff] [blame] | 218 | owner = arch_spin_yield_target(READ_ONCE(lp->lock), NULL); |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 219 | if (owner && arch_vcpu_is_preempted(owner - 1)) |
| 220 | smp_yield_cpu(owner - 1); |
| 221 | |
| 222 | count = spin_retry; |
| 223 | while (1) { |
| 224 | old = arch_load_niai4(&lp->lock); |
| 225 | owner = old & _Q_LOCK_CPU_MASK; |
| 226 | /* Try to get the lock if it is free. */ |
| 227 | if (!owner) { |
| 228 | new = (old & _Q_TAIL_MASK) | lockval; |
Heiko Carstens | 78ca4fe | 2017-11-14 13:47:00 +0100 | [diff] [blame] | 229 | if (arch_cmpxchg_niai8(&lp->lock, old, new)) { |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 230 | /* Got the lock */ |
Heiko Carstens | 78ca4fe | 2017-11-14 13:47:00 +0100 | [diff] [blame] | 231 | return; |
| 232 | } |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 233 | continue; |
| 234 | } |
| 235 | if (count-- >= 0) |
| 236 | continue; |
| 237 | count = spin_retry; |
| 238 | if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(owner - 1)) |
| 239 | smp_yield_cpu(owner - 1); |
| 240 | } |
| 241 | } |
| 242 | |
Thomas Gleixner | 0199c4e | 2009-12-02 20:01:25 +0100 | [diff] [blame] | 243 | void arch_spin_lock_wait(arch_spinlock_t *lp) |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 244 | { |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 245 | if (test_cpu_flag(CIF_DEDICATED_CPU)) |
| 246 | arch_spin_lock_queued(lp); |
| 247 | else |
| 248 | arch_spin_lock_classic(lp); |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 249 | } |
Thomas Gleixner | 0199c4e | 2009-12-02 20:01:25 +0100 | [diff] [blame] | 250 | EXPORT_SYMBOL(arch_spin_lock_wait); |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 251 | |
Philipp Hachtmann | 5b3f683 | 2014-04-07 18:25:23 +0200 | [diff] [blame] | 252 | int arch_spin_trylock_retry(arch_spinlock_t *lp) |
| 253 | { |
Martin Schwidefsky | 02c503ff | 2016-11-28 15:50:48 +0100 | [diff] [blame] | 254 | int cpu = SPINLOCK_LOCKVAL; |
| 255 | int owner, count; |
Philipp Hachtmann | 5b3f683 | 2014-04-07 18:25:23 +0200 | [diff] [blame] | 256 | |
Martin Schwidefsky | 2c72a44 | 2015-01-14 17:52:33 +0100 | [diff] [blame] | 257 | for (count = spin_retry; count > 0; count--) { |
Christian Borntraeger | 187b5f4 | 2017-02-10 12:34:49 +0100 | [diff] [blame] | 258 | owner = READ_ONCE(lp->lock); |
Martin Schwidefsky | 2c72a44 | 2015-01-14 17:52:33 +0100 | [diff] [blame] | 259 | /* Try to get the lock if it is free. */ |
| 260 | if (!owner) { |
Martin Schwidefsky | 02c503ff | 2016-11-28 15:50:48 +0100 | [diff] [blame] | 261 | if (__atomic_cmpxchg_bool(&lp->lock, 0, cpu)) |
Martin Schwidefsky | 2c72a44 | 2015-01-14 17:52:33 +0100 | [diff] [blame] | 262 | return 1; |
Martin Schwidefsky | b13de4b | 2017-03-24 17:00:45 +0100 | [diff] [blame] | 263 | } |
Martin Schwidefsky | 2c72a44 | 2015-01-14 17:52:33 +0100 | [diff] [blame] | 264 | } |
Philipp Hachtmann | 5b3f683 | 2014-04-07 18:25:23 +0200 | [diff] [blame] | 265 | return 0; |
| 266 | } |
| 267 | EXPORT_SYMBOL(arch_spin_trylock_retry); |
| 268 | |
Martin Schwidefsky | eb3b7b8 | 2017-03-24 17:32:23 +0100 | [diff] [blame] | 269 | void arch_read_lock_wait(arch_rwlock_t *rw) |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 270 | { |
Martin Schwidefsky | eb3b7b8 | 2017-03-24 17:32:23 +0100 | [diff] [blame] | 271 | if (unlikely(in_interrupt())) { |
| 272 | while (READ_ONCE(rw->cnts) & 0x10000) |
| 273 | barrier(); |
| 274 | return; |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 275 | } |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 276 | |
Martin Schwidefsky | eb3b7b8 | 2017-03-24 17:32:23 +0100 | [diff] [blame] | 277 | /* Remove this reader again to allow recursive read locking */ |
| 278 | __atomic_add_const(-1, &rw->cnts); |
| 279 | /* Put the reader into the wait queue */ |
| 280 | arch_spin_lock(&rw->wait); |
| 281 | /* Now add this reader to the count value again */ |
| 282 | __atomic_add_const(1, &rw->cnts); |
| 283 | /* Loop until the writer is done */ |
| 284 | while (READ_ONCE(rw->cnts) & 0x10000) |
| 285 | barrier(); |
| 286 | arch_spin_unlock(&rw->wait); |
| 287 | } |
| 288 | EXPORT_SYMBOL(arch_read_lock_wait); |
| 289 | |
| 290 | void arch_write_lock_wait(arch_rwlock_t *rw) |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 291 | { |
Martin Schwidefsky | 02c503ff | 2016-11-28 15:50:48 +0100 | [diff] [blame] | 292 | int old; |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 293 | |
Martin Schwidefsky | eb3b7b8 | 2017-03-24 17:32:23 +0100 | [diff] [blame] | 294 | /* Add this CPU to the write waiters */ |
| 295 | __atomic_add(0x20000, &rw->cnts); |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 296 | |
Martin Schwidefsky | eb3b7b8 | 2017-03-24 17:32:23 +0100 | [diff] [blame] | 297 | /* Put the writer into the wait queue */ |
| 298 | arch_spin_lock(&rw->wait); |
Martin Schwidefsky | bbae71b | 2014-09-22 16:34:38 +0200 | [diff] [blame] | 299 | |
Martin Schwidefsky | bbae71b | 2014-09-22 16:34:38 +0200 | [diff] [blame] | 300 | while (1) { |
Martin Schwidefsky | eb3b7b8 | 2017-03-24 17:32:23 +0100 | [diff] [blame] | 301 | old = READ_ONCE(rw->cnts); |
| 302 | if ((old & 0x1ffff) == 0 && |
| 303 | __atomic_cmpxchg_bool(&rw->cnts, old, old | 0x10000)) |
| 304 | /* Got the lock */ |
Martin Schwidefsky | bbae71b | 2014-09-22 16:34:38 +0200 | [diff] [blame] | 305 | break; |
Martin Schwidefsky | eb3b7b8 | 2017-03-24 17:32:23 +0100 | [diff] [blame] | 306 | barrier(); |
Martin Schwidefsky | bbae71b | 2014-09-22 16:34:38 +0200 | [diff] [blame] | 307 | } |
Martin Schwidefsky | eb3b7b8 | 2017-03-24 17:32:23 +0100 | [diff] [blame] | 308 | |
| 309 | arch_spin_unlock(&rw->wait); |
Martin Schwidefsky | bbae71b | 2014-09-22 16:34:38 +0200 | [diff] [blame] | 310 | } |
Martin Schwidefsky | eb3b7b8 | 2017-03-24 17:32:23 +0100 | [diff] [blame] | 311 | EXPORT_SYMBOL(arch_write_lock_wait); |
Martin Schwidefsky | bbae71b | 2014-09-22 16:34:38 +0200 | [diff] [blame] | 312 | |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 313 | void arch_spin_relax(arch_spinlock_t *lp) |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 314 | { |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 315 | int cpu; |
Martin Schwidefsky | 951f22d | 2005-07-27 11:44:57 -0700 | [diff] [blame] | 316 | |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 317 | cpu = READ_ONCE(lp->lock) & _Q_LOCK_CPU_MASK; |
Martin Schwidefsky | d59b93d | 2014-09-19 14:29:31 +0200 | [diff] [blame] | 318 | if (!cpu) |
| 319 | return; |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 320 | if (MACHINE_IS_LPAR && !arch_vcpu_is_preempted(cpu - 1)) |
Martin Schwidefsky | d59b93d | 2014-09-19 14:29:31 +0200 | [diff] [blame] | 321 | return; |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 322 | smp_yield_cpu(cpu - 1); |
Martin Schwidefsky | d59b93d | 2014-09-19 14:29:31 +0200 | [diff] [blame] | 323 | } |
Martin Schwidefsky | b96f7d8 | 2017-03-24 17:25:02 +0100 | [diff] [blame] | 324 | EXPORT_SYMBOL(arch_spin_relax); |