Copyright (c) 2002 The NetBSD Foundation, Inc.
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.Dd September 21, 2002 .Dt CPU_IDLE 9 .Os .Sh NAME .Nm cpu_idle .Nd idle CPU while waiting for work .Sh SYNOPSIS n sys/proc.h .Ft void .Fn cpu_idle "void" .Sh DESCRIPTION The .Fn cpu_idle function is invoked to idle the current CPU while waiting for work to be done. It is primarily called by the scheduler if no processes are available on the system run queue. The .Fn cpu_idle function is a machine-dependent implementations in order to permit low-level CPU control.
p The .Fn cpu_idle function must be called with the scheduler lock held
see Xr SCHED_LOCK 9 and at the .Xr splsched 9 interrupt protection level. It performs the following operations: l -bullet t Release the scheduler lock. t Lower the current interrupt priority level to permit interrupts to be taken that will eventually cause processes to appear again on the system run queue. t Try to zero some pages for the virtual memory system. t Perform any CPU or system power control. t Wait until a process appears on the system run queue. t Acquire the scheduler lock. .El
p For CPUs which don't support an idle operation, the CPU must spin until a process appears on the system run queue. Generally, this is done by checking if the .Va sched_whichqs variable in the scheduler is not zero. See .Xr setrunqueue 9 for further details. .Sh SEE ALSO .Xr mi_switch 9 , .Xr scheduler 9 , .Xr setrunqueue 9 , .Xr spl 9 , .Xr uvm 9
Indexes created Fri Oct 03 02:09:57 GMT 2025