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#ifndef __LINUX_BIT_SPINLOCK_H
#define __LINUX_BIT_SPINLOCK_H
#include <linux/kernel.h>
#include <linux/preempt.h>
#include <linux/futex.h>
#include <urcu/futex.h>
/*
* The futex wait op wants an explicit 32-bit address and value. If the bitmap
* used for the spinlock is 64-bit, cast down and pass the right 32-bit region
* for the in-kernel checks. The value is the copy that has already been read
* from the atomic op.
*
* The futex wake op interprets the value as the number of waiters to wake (up
* to INT_MAX), so pass that along directly.
*/
static inline void do_futex(int nr, unsigned long *addr, unsigned long v, int futex_flags)
{
u32 *addr32 = (u32 *) addr;
u32 *v32 = (u32 *) &v;
int shift = 0;
futex_flags |= FUTEX_PRIVATE_FLAG;
#if BITS_PER_LONG == 64
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
shift = (nr >= 32) ? 1 : 0;
#else
shift = (nr < 32) ? 1 : 0;
#endif
#endif
if (shift) {
addr32 += shift;
v32 += shift;
}
/*
* The shift to determine the futex address may have cast away a
* literal wake count value. The value is capped to INT_MAX and thus
* always in the low bytes of v regardless of bit nr. Copy in the wake
* count to whatever 32-bit range was selected.
*/
if (futex_flags == FUTEX_WAKE_PRIVATE)
*v32 = (u32) v;
futex(addr32, futex_flags, *v32, NULL, NULL, 0);
}
static inline void bit_spin_lock(int nr, unsigned long *_addr)
{
unsigned long mask;
unsigned long *addr = _addr + (nr / BITS_PER_LONG);
unsigned long v;
nr &= BITS_PER_LONG - 1;
mask = 1UL << nr;
while (1) {
v = __atomic_fetch_or(addr, mask, __ATOMIC_ACQUIRE);
if (!(v & mask))
break;
do_futex(nr, addr, v, FUTEX_WAIT);
}
}
static inline void bit_spin_wake(int nr, unsigned long *_addr)
{
do_futex(nr, _addr, INT_MAX, FUTEX_WAKE);
}
static inline void bit_spin_unlock(int nr, unsigned long *_addr)
{
unsigned long mask;
unsigned long *addr = _addr + (nr / BITS_PER_LONG);
nr &= BITS_PER_LONG - 1;
mask = 1UL << nr;
__atomic_and_fetch(addr, ~mask, __ATOMIC_RELEASE);
do_futex(nr, addr, INT_MAX, FUTEX_WAKE);
}
#endif /* __LINUX_BIT_SPINLOCK_H */
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