NAME

splhi, spllo, splx, islo − enable and disable interrupts

SYNOPSIS

intspllo(void);

intsplhi(void);

voidsplx(int x);

intislo(void);

DESCRIPTION

These primitives enable and disable maskable interrupts on the current processor.  Generally, device drivers should use ­ilock (see lock(10.2)), sleep(10.2), or the functions in qio(10.2) to control interaction between processes and interrupt handlers. Those routines (but not these) provide correct synchronisation on multiprocessors.

­Spllo enables interrupts and returns a flag representing the previous interrupt enable state.  It must not normally be called from interrupt level. 

­Splhi disables all maskable interrupts and returns the previous interrupt enable state.  The period during which interrupts are disabled had best be short, or real-time applications will suffer. 

­Splx restores the interrupt enable state state to x, which must be a value returned by a previous call to ­splhi or spllo.

­Islo returns true (non-zero) if interrupts are currently enabled, and 0 otherwise. 

SEE ALSO

lock(10.2), qio(10.2), sleep(10.2), intrenable(10.2)

Plan 9  —  June 08, 2000