save_flags

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
AVAILABILITY
SEE ALSO
AUTHOR
BUGS

NAME

save_flags, restore_flags − save/restore processor state and irq mask

SYNOPSIS

#include

unsigned long flags;
void save_flags(flags)
void restore_flags(flags)

DESCRIPTION

The save_flags and restore_flags macros cooperate with the cli function to provide interrupt protection to critical sections of code. The save_flags function saves the current processor state, most specifically the interrupt priority level, in the flags value (which must be an l-value). The flags must be passed to a subsequent call to restore_flags to restore the processor state.

The save_flags macro does not affect the processor state, but drivers may use the cli(9) and sti functions to disable and enable interrupts after saving the current flags. When the critical section of code is passed, the restore_flags returns the processor to its state at the point where the matching save_flags was called.

Only values returned by save_flags can be passed to restore_flags. Any other values may cause unpredictable results, and are certainly not portable.

RETURN VALUE

The restore_flags macro saves the processor state in the flags parameter, which must be a non-const l-value.

AVAILABILITY

Linux 1.0+

SEE ALSO

cli(9)

AUTHOR

Stephen Williams (steve@icarus.com)

BUGS

How does all this react with symmetric multiprocessor machines?