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spl(9r)
NAME
  spl - General: Sets the processor priority to mask different levels of
  interrupts

SYNOPSIS
  #include <machine/cpu.h>

  int getspl(
	  void );

  int splbio(
	  void );

  int splclock(
	  void );

  int spldevhigh(
	  void );

  int splextreme(
	  void );

  int splhigh(
	  void );

  int splimp(
	  void );

  int splnet(
	  void );

  int splnone(
	  void );

  int splsched(
	  void );

  int splsoftclock(
	  void );

  int spltty(
	  void );

  int splvm(
	  void );

  int splx(
	  int x );

ARGUMENTS
  x   Specifies a CPU priority level. This level must be a value returned by
      a previous call to one of the spl routines.

DESCRIPTION
  The operating system	supports the naming of spl routines to indicate the
  associated device types. Named spl routines make it easier to determine
  which routine you should use to set the priority level for a given device
  type. The following table summarizes the uses for the different spl
  routines:

  getspl  Obtains the spl value.

  splbio  Masks all disk and tape controller interrupts.

  splclock
	  Masks all hardware clock interrupts.

  spldevhigh
	  Masks all device and software interrupts.

  splextreme
	  Blocks against all but halt interrupts.

  splhigh Masks all interrupts except for realtime devices, machine checks,
	  and halt interrupts.

  splimp  Masks all LAN hardware interrupts.

  splnet  Masks all network software interrupts.

  splnone Unmasks (enables) all interrupts.

  splsched
	  Masks all scheduling interrupts (usually the hardware clock).

  splsoftclock
	  Masks all software clock interrupts.

  spltty  Masks all tty (terminal device) interrupts.

  splvm	  Masks all virtual memory clock interrupts.

  splx	  Resets the CPU priority to the level specified by the argument.

NOTES
  The binding of any spl routine with a specific CPU priority level is highly
  machine dependent. With the exceptions of the splhigh and splnone routines,
  knowledge of the explicit bindings is not required to create new device
  drivers. You always use splhigh to mask (disable) all interrupts and
  splnone to unmask (enable) all interrupts.

RETURN VALUES
  Upon successful completion, each spl routine returns an integer value that
  represents the CPU priority level that existed before it was changed by a
  call to the specified spl routine.

EXAMPLE
  The following code fragment shows the use of spl routines as part of a disk
  strategy routine:

       int s;
	.
	.
	.
       s = splbio(); /* Mask (disable) all disk interrupts */
	.
	.
	.
       [Code to deal with data that can be modified by the disk interrupt
       code]
	.
	.
	.
       splx(s); /* Restore CPU priority to what it was */

Index for Section 9r

Alphabetical listing for S

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