bitops.h File Reference

x86 bit operations More...

#include <stdint.h>

Go to the source code of this file.

Functions
	FILE_LICENCE (GPL2_OR_LATER_OR_UBDL)
static	__attribute__ ((always_inline)) void set_bit(unsigned int bit
	Set bit atomically. More...
__asm__	__volatile__ ("lock btsl %k1, %0" :"+m"(*bytes) :"Ir"(bit))
__asm__	__volatile__ ("lock btrl %k1, %0" :"+m"(*bytes) :"Ir"(bit))
__asm__	__volatile__ ("lock btsl %k2, %0\n\t" "sbb %1, %1\n\t" :"+m"(*bytes), "=r"(old) :"Ir"(bit))
__asm__	__volatile__ ("lock btrl %k2, %0\n\t" "sbb %1, %1\n\t" :"+m"(*bytes), "=r"(old) :"Ir"(bit))

Variables
static volatile void *	bits
int	old

Detailed Description

x86 bit operations

We perform atomic bit set and bit clear operations using "lock bts" and "lock btr". We use the output constraint to inform the compiler that any memory from the start of the bit field up to and including the byte containing the bit may be modified. (This is overkill but shouldn't matter in practice since we're unlikely to subsequently read other bits from the same bit field.)

Definition in file bitops.h.

Function Documentation

FILE_LICENCE()

FILE_LICENCE

(

GPL2_OR_LATER_OR_UBDL

)

__attribute__()

static __attribute__ ( (always_inline)  )

inlinestatic

Set bit atomically.

Test and clear bit atomically.

Test and set bit atomically.

Clear bit atomically.

Parameters

bit	Bit to set
bits	Bit field
bit	Bit to set
bits	Bit field

Return values

old	Old value of bit (zero or non-zero)

__volatile__() [1/4]

__asm__ __volatile__	(	"lock btsl %	k1,
		%0" :"+m"*bytes :"Ir"	bit
	)

__volatile__() [2/4]

__asm__ __volatile__	(	"lock btrl %	k1,
		%0" :"+m"*bytes :"Ir"	bit
	)

__volatile__() [3/4]

__asm__ __volatile__	(	"lock btsl %	k2,
		%0\n\t" "sbb %	1,
		%1\n\t" :"+m"*	bytes
	)

__volatile__() [4/4]

__asm__ __volatile__	(	"lock btrl %	k2,
		%0\n\t" "sbb %	1,
		%1\n\t" :"+m"*	bytes
	)

Variable Documentation

bits

static volatile void * bits

Initial value:

{
        volatile struct {
                uint8_t byte[ ( bit / 8 ) + 1 ];
        } *bytes = bits

Definition at line 27 of file bitops.h.

Referenced by _tg3_flag(), _tg3_flag_clear(), _tg3_flag_set(), arbel_bitmask_alloc(), arbel_bitmask_free(), asn1_bit_string(), asn1_integral_bit_string(), ath5k_hw_bitswap(), ath9k_hw_getrxfilter(), ath9k_hw_setrxfilter(), bitops_test_exec(), deflate_alphabet(), deflate_bin(), deflate_consume(), deflate_dump_alphabet(), deflate_inflate(), deflate_init(), deflate_set_length(), hermon_bitmask_alloc(), hermon_bitmask_free(), hub_complete(), mdio_sync(), net80211_duration(), png_pixels_pass(), rol32(), ror16(), ror32(), rsa_parse_mod_exp(), smc_read_phy_register(), and smc_write_phy_register().

old

return old

Definition at line 64 of file bitops.h.

Referenced by efi_file_path_claim(), generic_settings_store(), tcp_sack(), and usbkbd_report().