Files
@ 0d186246d211
Branch filter:
Location: vmkdrivers/BLD/build/HEADERS/KLnext-vmkdrivers-asm-x64/vmkernel64/release/asm/rwsem.h
0d186246d211
7.4 KiB
text/x-chdr
ESXi-4.1-U3
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 | /* rwsem.h: R/W semaphores implemented using XADD/CMPXCHG for x86_64+
*
* Written by David Howells (dhowells@redhat.com).
* Ported by Andi Kleen <ak@suse.de> to x86-64.
*
* Derived from asm-i386/semaphore.h and asm-i386/rwsem.h
*
*
* The MSW of the count is the negated number of active writers and waiting
* lockers, and the LSW is the total number of active locks
*
* The lock count is initialized to 0 (no active and no waiting lockers).
*
* When a writer subtracts WRITE_BIAS, it'll get 0xffff0001 for the case of an
* uncontended lock. This can be determined because XADD returns the old value.
* Readers increment by 1 and see a positive value when uncontended, negative
* if there are writers (and maybe) readers waiting (in which case it goes to
* sleep).
*
* The value of WAITING_BIAS supports up to 32766 waiting processes. This can
* be extended to 65534 by manually checking the whole MSW rather than relying
* on the S flag.
*
* The value of ACTIVE_BIAS supports up to 65535 active processes.
*
* This should be totally fair - if anything is waiting, a process that wants a
* lock will go to the back of the queue. When the currently active lock is
* released, if there's a writer at the front of the queue, then that and only
* that will be woken up; if there's a bunch of consecutive readers at the
* front, then they'll all be woken up, but no other readers will be.
*/
#ifndef _X8664_RWSEM_H
#define _X8664_RWSEM_H
#ifndef _LINUX_RWSEM_H
#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
#endif
#ifdef __KERNEL__
#include <linux/list.h>
#include <linux/spinlock.h>
struct rwsem_waiter;
extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *);
extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
/*
* the semaphore definition
*/
struct rw_semaphore {
signed int count;
#define RWSEM_UNLOCKED_VALUE 0x00000000
#define RWSEM_ACTIVE_BIAS 0x00000001
#define RWSEM_ACTIVE_MASK 0x0000ffff
#define RWSEM_WAITING_BIAS (-0x00010000)
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
spinlock_t wait_lock;
struct list_head wait_list;
#if RWSEM_DEBUG
int debug;
#endif
};
/*
* initialisation
*/
#if RWSEM_DEBUG
#define __RWSEM_DEBUG_INIT , 0
#else
#define __RWSEM_DEBUG_INIT /* */
#endif
#define __RWSEM_INITIALIZER(name) \
{ RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) \
__RWSEM_DEBUG_INIT }
#define DECLARE_RWSEM(name) \
struct rw_semaphore name = __RWSEM_INITIALIZER(name)
static inline void init_rwsem(struct rw_semaphore *sem)
{
sem->count = RWSEM_UNLOCKED_VALUE;
spin_lock_init(&sem->wait_lock);
INIT_LIST_HEAD(&sem->wait_list);
#if RWSEM_DEBUG
sem->debug = 0;
#endif
}
/*
* lock for reading
*/
static inline void __down_read(struct rw_semaphore *sem)
{
__asm__ __volatile__(
"# beginning down_read\n\t"
LOCK_PREFIX " incl (%%rdi)\n\t" /* adds 0x00000001, returns the old value */
" js 2f\n\t" /* jump if we weren't granted the lock */
"1:\n\t"
LOCK_SECTION_START("") \
"2:\n\t"
" call rwsem_down_read_failed_thunk\n\t"
" jmp 1b\n"
LOCK_SECTION_END \
"# ending down_read\n\t"
: "+m"(sem->count)
: "D"(sem)
: "memory", "cc");
}
/*
* trylock for reading -- returns 1 if successful, 0 if contention
*/
static inline int __down_read_trylock(struct rw_semaphore *sem)
{
__s32 result, tmp;
__asm__ __volatile__(
"# beginning __down_read_trylock\n\t"
" movl %0,%1\n\t"
"1:\n\t"
" movl %1,%2\n\t"
" addl %3,%2\n\t"
" jle 2f\n\t"
LOCK_PREFIX " cmpxchgl %2,%0\n\t"
" jnz 1b\n\t"
"2:\n\t"
"# ending __down_read_trylock\n\t"
: "+m"(sem->count), "=&a"(result), "=&r"(tmp)
: "i"(RWSEM_ACTIVE_READ_BIAS)
: "memory", "cc");
return result>=0 ? 1 : 0;
}
/*
* lock for writing
*/
static inline void __down_write(struct rw_semaphore *sem)
{
int tmp;
tmp = RWSEM_ACTIVE_WRITE_BIAS;
__asm__ __volatile__(
"# beginning down_write\n\t"
LOCK_PREFIX " xaddl %0,(%%rdi)\n\t" /* subtract 0x0000ffff, returns the old value */
" testl %0,%0\n\t" /* was the count 0 before? */
" jnz 2f\n\t" /* jump if we weren't granted the lock */
"1:\n\t"
LOCK_SECTION_START("")
"2:\n\t"
" call rwsem_down_write_failed_thunk\n\t"
" jmp 1b\n"
LOCK_SECTION_END
"# ending down_write"
: "=&r" (tmp)
: "0"(tmp), "D"(sem)
: "memory", "cc");
}
/*
* trylock for writing -- returns 1 if successful, 0 if contention
*/
static inline int __down_write_trylock(struct rw_semaphore *sem)
{
signed long ret = cmpxchg(&sem->count,
RWSEM_UNLOCKED_VALUE,
RWSEM_ACTIVE_WRITE_BIAS);
if (ret == RWSEM_UNLOCKED_VALUE)
return 1;
return 0;
}
/*
* unlock after reading
*/
static inline void __up_read(struct rw_semaphore *sem)
{
__s32 tmp = -RWSEM_ACTIVE_READ_BIAS;
__asm__ __volatile__(
"# beginning __up_read\n\t"
LOCK_PREFIX " xaddl %[tmp],(%%rdi)\n\t" /* subtracts 1, returns the old value */
" js 2f\n\t" /* jump if the lock is being waited upon */
"1:\n\t"
LOCK_SECTION_START("")
"2:\n\t"
" decw %w[tmp]\n\t" /* do nothing if still outstanding active readers */
" jnz 1b\n\t"
" call rwsem_wake_thunk\n\t"
" jmp 1b\n"
LOCK_SECTION_END
"# ending __up_read\n"
: "+m"(sem->count), [tmp] "+r" (tmp)
: "D"(sem)
: "memory", "cc");
}
/*
* unlock after writing
*/
static inline void __up_write(struct rw_semaphore *sem)
{
unsigned tmp;
__asm__ __volatile__(
"# beginning __up_write\n\t"
" movl %[bias],%[tmp]\n\t"
LOCK_PREFIX " xaddl %[tmp],(%%rdi)\n\t" /* tries to transition 0xffff0001 -> 0x00000000 */
" jnz 2f\n\t" /* jump if the lock is being waited upon */
"1:\n\t"
LOCK_SECTION_START("")
"2:\n\t"
" decw %w[tmp]\n\t" /* did the active count reduce to 0? */
" jnz 1b\n\t" /* jump back if not */
" call rwsem_wake_thunk\n\t"
" jmp 1b\n"
LOCK_SECTION_END
"# ending __up_write\n"
: "+m"(sem->count), [tmp] "=r" (tmp)
: "D"(sem), [bias] "i"(-RWSEM_ACTIVE_WRITE_BIAS)
: "memory", "cc");
}
/*
* downgrade write lock to read lock
*/
static inline void __downgrade_write(struct rw_semaphore *sem)
{
__asm__ __volatile__(
"# beginning __downgrade_write\n\t"
LOCK_PREFIX " addl %[bias],(%%rdi)\n\t" /* transitions 0xZZZZ0001 -> 0xYYYY0001 */
" js 2f\n\t" /* jump if the lock is being waited upon */
"1:\n\t"
LOCK_SECTION_START("")
"2:\n\t"
" call rwsem_downgrade_thunk\n"
" jmp 1b\n"
LOCK_SECTION_END
"# ending __downgrade_write\n"
: "=m"(sem->count)
: "D"(sem), [bias] "i"(-RWSEM_WAITING_BIAS), "m"(sem->count)
: "memory", "cc");
}
/*
* implement atomic add functionality
*/
static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
{
__asm__ __volatile__(
LOCK_PREFIX "addl %1,%0"
:"=m"(sem->count)
:"ir"(delta), "m"(sem->count));
}
/*
* implement exchange and add functionality
*/
static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
{
int tmp = delta;
__asm__ __volatile__(
LOCK_PREFIX "xaddl %0,(%2)"
: "=r"(tmp), "=m"(sem->count)
: "r"(sem), "m"(sem->count), "0" (tmp)
: "memory");
return tmp+delta;
}
#endif /* __KERNEL__ */
#endif /* _X8664_RWSEM_H */
|