ref: c309f466eff33a331f9a8d8c8b18cfe613c1d3f4
dir: /sys/man/9/splhi/
.TH SPLHI 9 .SH NAME splhi, spllo, splx, islo \- enable and disable interrupts .SH SYNOPSIS .ta \w'\fLvoid 'u .B int spllo(void) .PP .B int splhi(void) .PP .B void splx(int x) .PP .B int islo(void) .SH DESCRIPTION These primitives enable and disable maskable interrupts on the current processor. Generally, device drivers should use .I ilock (see .IR lock (9)), .IR sleep (9), or the functions in .IR qio (9) to control interaction between processes and interrupt handlers. Those routines (but not these) provide correct synchronisation on multiprocessors. .PP .I Spllo enables interrupts and returns a flag representing the previous interrupt enable state. It must not normally be called from interrupt level. .PP .I 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. .PP .I Splx restores the interrupt enable state to .IR x , which must be a value returned by a previous call to .I splhi or .IR spllo . .PP .I Islo returns true (non-zero) if interrupts are currently enabled, and 0 otherwise. .SH SOURCE .B /sys/src/9/*/l.s .SH SEE ALSO .IR lock (9), .IR qio (9), .IR sleep (9), .IR intrenable (9)