save_flags(9) Linux Kernel Functions save_flags(9)NAME
save_flags, restore_flags - save/restore processor state and irq mask
SYNOPSIS
#include <asm/system.h>
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 specifi‐
cally 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 parame‐
ter, which must be a non-const l-value.
AVAILABILITY
Linux 1.0+
SEE ALSOcli(9)AUTHOR
Stephen Williams (steve@icarus.com)
BUGS
How does all this react with symmetric multiprocessor machines?
Linux DDI $Date:$ save_flags(9)
