ucas(9) [netbsd man page]

UCAS(9) 						   BSD Kernel Developer's Manual						   UCAS(9)

NAME

     ucas -- atomic memory operations on user-space address

SYNOPSIS

     #include <sys/systm.h>

     int
     ucas_ptr(volatile void *uptr, void *old, void *new, void *retp);

     int
     ucas_int(volatile int *uptr, int old, int new, int *retp);

DESCRIPTION

     These functions provide compare-and-swap (CAS) functionality on user-space address.

     Except that they can be safely used for the kernel to access user-space address, they are semantically equivalents of atomic_cas(3).

     uptr  The pointer to the variable.  This should be a user-space pointer.

     old   The value to compare with the variable.

     new   The value to store to the variable.

     retp  The pointer to the memory to store the old value of the variable.

RETURN VALUES

     On success, these functions return 0.  In that case, the caller can consult the value returned via retp to check the result of the CAS opera-
     tion.  Otherwise, these functions return an appropriate errno(9) error code, typically EFAULT.

SEE ALSO

     atomic_cas(3), intro(9)

BUGS

     Conceptually, the retp argument of ucas_ptr() would be of void **.  The current prototype is a compromise for usability.

BSD
								 October 24, 2011							       BSD

STORE(9)						   BSD Kernel Developer's Manual						  STORE(9)

NAME

     store, subyte, suswintr, suword -- store data to user-space

SYNOPSIS

     #include <sys/types.h>
     #include <sys/time.h>
     #include <sys/systm.h>

     int
     subyte(volatile void *base, int byte);

     int
     suword(volatile void *base, long word);

     int
     suword16(volatile void *base, int word);

     int
     suword32(volatile void *base, int32_t word);

     int
     suword64(volatile void *base, int64_t word);

     #include <sys/resourcevar.h>

     int
     suswintr(void *base, int word);

DESCRIPTION

     The store functions are designed to copy small amounts of data to user-space.  If write is successful, it is performed atomically.  The data
     written must be naturally aligned.

     The store routines provide the following functionality:

     subyte()	 Stores a byte of data to the user-space address base.

     suword()	 Stores a word of data to the user-space address base.

     suword16()  Stores 16 bits of data to the user-space address base.

     suword32()  Stores 32 bits of data to the user-space address base.

     suword64()  Stores 64 bits of data to the user-space address base.

     suswintr()  Stores a short word of data to the user-space address base.  This function is safe to call during an interrupt context.

RETURN VALUES

     The store functions return 0 on success or -1 on failure.

SEE ALSO

     copy(9), fetch(9)

BSD
								 October 29, 2014							       BSD