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Diffstat (limited to 'newlib/libc/sys/amdgcn/lock.c')
| -rw-r--r-- | newlib/libc/sys/amdgcn/lock.c | 187 |
1 files changed, 187 insertions, 0 deletions
diff --git a/newlib/libc/sys/amdgcn/lock.c b/newlib/libc/sys/amdgcn/lock.c new file mode 100644 index 0000000..dcc93cb --- /dev/null +++ b/newlib/libc/sys/amdgcn/lock.c @@ -0,0 +1,187 @@ +/* + * Support file for amdgcn in newlib. + * Copyright (c) 2024 BayLibre. + * + * The authors hereby grant permission to use, copy, modify, distribute, + * and license this software and its documentation for any purpose, provided + * that existing copyright notices are retained in all copies and that this + * notice is included verbatim in any distributions. No written agreement, + * license, or royalty fee is required for any of the authorized uses. + * Modifications to this software may be copyrighted by their authors + * and need not follow the licensing terms described here, provided that + * the new terms are clearly indicated on the first page of each file where + * they apply. + */ + +/* Lock routines for AMD GPU devices. + + The lock is a 32-bit int: + - bits 0-3: wavefront id + - bits 4-23: workgroup id (+1, so never zero) + - bits 24-31: recursive lock count. + + The purpose of the "relaxed" loads and stores being "atomic" here is + mostly just to ensure we punch through the caches consistently. + + Non-recursive locks may be unlocked by any thread. It's an error to + attempt to unlock a recursive lock from the wrong thread. + + The DEBUG statements here use sprintf and write to avoid taking locks + themselves. */ + +#include <sys/lock.h> +#include <assert.h> + +#define DEBUG 0 + +#if DEBUG +extern void write(int, char *, int); +#endif + +static unsigned +__gcn_thread_id () +{ + /* Dim(0) is the workgroup ID; range 0 to maybe thousands. + Dim(1) is the wavefront ID; range 0 to 15. */ + return (((__builtin_gcn_dim_pos (0) + 1) << 4) + + __builtin_gcn_dim_pos (1)); +} + +static int +__gcn_lock_acquire_int (_LOCK_T *lock_ptr, int _try) +{ + int id = __gcn_thread_id (); + +#if DEBUG + char buf[1000]; + __builtin_sprintf (buf,"acquire:%p(%d) lock_value:0x%x id:0x%x", lock_ptr, + _try, *lock_ptr, id); + write (1, buf, __builtin_strlen(buf)); +#endif + + int expected = 0; + while (!__atomic_compare_exchange_n (lock_ptr, &expected, id, 0, + __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)) + { + /* Lock *not* acquired. */ + if (_try) + return 0; + else + { + asm ("s_sleep 64"); + expected = 0; + } + } + +#if DEBUG + __builtin_sprintf (buf,"acquired:%p(%d) lock_value:0x%x id:0x%x", lock_ptr, + _try, *lock_ptr, id); + write (1, buf, __builtin_strlen(buf)); +#endif + + return 1; +} + +int +__gcn_try_lock_acquire (_LOCK_T *lock_ptr) +{ + return __gcn_lock_acquire_int (lock_ptr, 1); +} + +void +__gcn_lock_acquire (_LOCK_T *lock_ptr) +{ + __gcn_lock_acquire_int (lock_ptr, 0); +} + +static int +__gcn_lock_acquire_recursive_int (_LOCK_T *lock_ptr, int _try) +{ + int id = __gcn_thread_id (); + +#if DEBUG + char buf[1000]; + __builtin_sprintf (buf,"acquire recursive:%p(%d) lock_value:0x%x id:0x%x", + lock_ptr, _try, *lock_ptr, id); + write (1, buf, __builtin_strlen(buf)); +#endif + + unsigned int lock_value = __atomic_load_n (lock_ptr, __ATOMIC_RELAXED); + if ((lock_value & 0xffffff) == id) + { + /* This thread already holds the lock. + Increment the recursion counter and update the lock. */ + int count = lock_value >> 24; + lock_value = ((count + 1) << 24) | id; + __atomic_store_n (lock_ptr, lock_value, __ATOMIC_RELAXED); + +#if DEBUG + __builtin_sprintf (buf, + "increment recursive:%p(%d) lock_value:0x%x id:0x%x", + lock_ptr, _try, *lock_ptr, id); + write (1, buf, __builtin_strlen(buf)); +#endif + + return 1; + } + else + return __gcn_lock_acquire_int (lock_ptr, _try); +} + +int +__gcn_lock_try_acquire_recursive (_LOCK_T *lock_ptr) +{ + return __gcn_lock_acquire_recursive_int (lock_ptr, 1); +} + +void +__gcn_lock_acquire_recursive (_LOCK_T *lock_ptr) +{ + __gcn_lock_acquire_recursive_int (lock_ptr, 0); +} + +void +__gcn_lock_release (_LOCK_T *lock_ptr) +{ +#if DEBUG + char buf[1000]; + __builtin_sprintf (buf,"release:%p lock_value:0x%x id:0x%x", lock_ptr, + *lock_ptr, __gcn_thread_id()); + write (1, buf, __builtin_strlen(buf)); +#endif + + __atomic_store_n (lock_ptr, 0, __ATOMIC_RELEASE); +} + +void +__gcn_lock_release_recursive (_LOCK_T *lock_ptr) +{ + int id = __gcn_thread_id (); + unsigned int lock_value = __atomic_load_n (lock_ptr, __ATOMIC_RELAXED); + +#if DEBUG + char buf[1000]; + __builtin_sprintf (buf, "release recursive:%p lock_value:0x%x id:0x%x", + lock_ptr, lock_value, id); + write (1, buf, __builtin_strlen(buf)); +#endif + + /* It is an error to call this function from the wrong thread. */ + assert ((lock_value & 0xffffff) == id); + + /* Decrement or release the lock. */ + int count = lock_value >> 24; + if (count > 0) + { + lock_value = ((count - 1) << 24) | id; + __atomic_store_n (lock_ptr, lock_value, __ATOMIC_RELAXED); + +#if DEBUG + __builtin_sprintf (buf, "decrement recursive:%p lock_value:0x%x id:0x%x", + lock_ptr, *lock_ptr, id); + write (1, buf, __builtin_strlen(buf)); +#endif + } + else + __gcn_lock_release (lock_ptr); +} |