casuword32(9) [freebsd man page]

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

NAME

     casueword, casueword32, casuword, casuword32 -- fetch, compare and store data from user-space

SYNOPSIS

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

     int
     casueword(volatile u_long *base, u_long oldval, u_long *oldvalp, u_long newval);

     int
     casueword32(volatile uint32_t *base, uint32_t oldval, uint32_t *oldvalp, uint32_t newval);

     u_long
     casuword(volatile u_long *base, u_long oldval, u_long newval);

     uint32_t
     casuword32(volatile uint32_t *base, uint32_t oldval, uint32_t newval);

DESCRIPTION

     The casueword functions are designed to perform atomic compare-and-swap operation on the value in the usermode memory of the current process.

     The casueword routines reads the value from user memory with address base, and compare the value read with oldval.  If the values are equal,
     newval is written to the *base.  In case of casueword32() and casueword(), old value is stored into the (kernel-mode) variable pointed by
     *oldvalp.	The userspace value must be naturally aligned.

     The callers of casuword() and casuword32() functions cannot distinguish between -1 read from userspace and function failure.

RETURN VALUES

     The casuword() and casuword32() functions return the data fetched or -1 on failure.  The casueword() and casueword32() functions return 0 on
     success and -1 on failure.

SEE ALSO

     atomic(9), fetch(9), store(9)

BSD
								 October 21, 2014							       BSD

atomic_cas(9F)						   Kernel Functions for Drivers 					    atomic_cas(9F)

NAME

       atomic_cas,   atomic_cas_8,   atomic_cas_uchar,	 atomic_cas_16,   atomic_cas_ushort,   atomic_cas_32,  atomic_cas_uint,  atomic_cas_ulong,
       atomic_cas_64, atomic_cas_ptr - atomic compare and swap operations

SYNOPSIS

       #include <sys/atomic.h>

       uint8_t atomic_cas_8(volatile uint8_t *target, uint8_t cmp, uint8_t
	    newval);

       uchar_t atomic_cas_uchar(volatile uchar_t *target, uchar_t cmp, uchar_t
	    newval);

       uint16_t atomic_cas_16(volatile uint16_t *target, uint16_t cmp, uint16_t
	    newval);

       ushort_t atomic_cas_ushort(volatile ushort_t *target, ushort_t cmp,
	    ushort_t newval);

       uint32_t atomic_cas_32(volatile uint32_t *target, uint32_t cmp, uint32_t
	    newval);

       uint_t atomic_cas_uint(volatile uint_t *target, uint_t cmp, uint_t newval);

       ulong_t atomic_cas_ulong(volatile ulong_t *target, ulong_t cmp, ulong_t
	    newval);

       uint64_t atomic_cas_64(volatile uint64_t *target, uint64_t cmp, uint64_t
	    newval);

       void *atomic_cas_ptr(volatile void *target, void *cmp, void *newval);

DESCRIPTION

       These functions enable a compare and swap operation to occur atomically. The value stored in target is compared with cmp. If  these  values
       are  equal,  the  value stored in target is replaced with newval. The old value stored in target is returned by the function whether or not
       the replacement occurred.

RETURN VALUES

       These functions return the old of *target.

ERRORS

       No errors are defined.

CONTEXT

       These functions can be called from user, interrupt, or kernel context.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+

SEE ALSO

       atomic_add(9F),	atomic_and(9F),  atomic_bits(9F),  atomic_dec(9F),   atomic_inc(9F),   atomic_or(9F),	atomic_swap(9F),   membar_ops(9F),
       attributes(5), atomic_ops(3C)

SunOS 5.11							    16 Jan 2006 						    atomic_cas(9F)