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UCS/RCACHE: Use built-in atomics for rwlock
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,105 @@ | ||
| /* | ||
| * Copyright (c) NVIDIA CORPORATION & AFFILIATES, 2024. ALL RIGHTS RESERVED. | ||
| * | ||
| * See file LICENSE for terms. | ||
| */ | ||
|
|
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| #ifndef UCS_RWLOCK_H | ||
| #define UCS_RWLOCK_H | ||
|
|
||
| /** | ||
| * The ucs_rwlock_t type. | ||
| * | ||
| * Readers increment the counter by UCS_RWLOCK_READ (4) | ||
| * Writers set the UCS_RWLOCK_WRITE bit when lock is held | ||
| * and set the UCS_RWLOCK_WAIT bit while waiting. | ||
| * | ||
| * 31 2 1 0 | ||
| * +-------------------+-+-+ | ||
| * | readers | | | | ||
| * +-------------------+-+-+ | ||
| * ^ ^ | ||
| * | | | ||
| * WRITE: lock held ----/ | | ||
| * WAIT: writer pending --/ | ||
| */ | ||
|
|
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| #define UCS_RWLOCK_WAIT 0x1 /* Writer is waiting */ | ||
| #define UCS_RWLOCK_WRITE 0x2 /* Writer has the lock */ | ||
| #define UCS_RWLOCK_MASK (UCS_RWLOCK_WAIT | UCS_RWLOCK_WRITE) | ||
| /* Writer is waiting or has lock */ | ||
| #define UCS_RWLOCK_READ 0x4 /* Reader increment */ | ||
|
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|
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| /** | ||
| * Read-write lock. | ||
| */ | ||
| typedef struct { | ||
| volatile int l; | ||
| } ucs_rwlock_t; | ||
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| static inline void ucs_rwlock_read_lock(ucs_rwlock_t *lock) { | ||
| int x; | ||
|
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| while (1) { | ||
| while (lock->l & UCS_RWLOCK_MASK) { | ||
| sched_yield(); | ||
| } | ||
|
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| x = __sync_fetch_and_add(&lock->l, UCS_RWLOCK_READ); | ||
| if (!(x & UCS_RWLOCK_MASK)) { | ||
| return; | ||
| } | ||
|
|
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| __sync_fetch_and_sub(&lock->l, UCS_RWLOCK_READ); | ||
| } | ||
| } | ||
|
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|
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| static inline void ucs_rwlock_read_unlock(ucs_rwlock_t *lock) { | ||
| __sync_fetch_and_sub(&lock->l, UCS_RWLOCK_READ); | ||
| } | ||
|
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|
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| static inline void ucs_rwlock_write_lock(ucs_rwlock_t *lock) { | ||
| int x; | ||
|
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| while (1) { | ||
| x = lock->l; | ||
| if ((x < UCS_RWLOCK_WRITE) && | ||
| (__sync_val_compare_and_swap(&lock->l, x, UCS_RWLOCK_WRITE) == x)) { | ||
| return; | ||
| } | ||
|
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| __sync_fetch_and_or(&lock->l, UCS_RWLOCK_WAIT); | ||
| while (lock->l > UCS_RWLOCK_WAIT) { | ||
| sched_yield(); | ||
| } | ||
| } | ||
| } | ||
|
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|
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| static inline int ucs_rwlock_write_trylock(ucs_rwlock_t *lock) { | ||
| int x; | ||
|
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| x = lock->l; | ||
| if ((x < UCS_RWLOCK_WRITE) && | ||
| (__sync_val_compare_and_swap(&lock->l, x, UCS_RWLOCK_WRITE) == x)) { | ||
| return 0; | ||
| } | ||
|
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| return -EBUSY; | ||
| } | ||
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| static inline void ucs_rwlock_write_unlock(ucs_rwlock_t *lock) { | ||
| __sync_fetch_and_sub(&lock->l, UCS_RWLOCK_WRITE); | ||
| } | ||
|
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| static inline void ucs_rwlock_init(ucs_rwlock_t *lock) { | ||
| lock->l = 0; | ||
| } | ||
|
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||
| #endif |
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