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drvr_register_shutdown(9r)
NAME
  drvr_register_shutdown - General: Registers or deregisters a shutdown
  interface

SYNOPSIS
  void drvr_register_shutdown(
	  void (*callback) (),
	  caddr_t parameter,
	  int flags );

ARGUMENTS
  callback
      Specifies the name of the device driver interface to be registered or
      deregistered by drvr_register_shutdown. When registered, this is the
      interface that the kernel calls when the system shuts down or halts.

  parameter
      Specifies a parameter that you want the kernel to pass to the device
      driver's registered shutdown interface. For example, you could pass a
      pointer to a softc structure or a pointer to a unit-specific data
      structure and the kernel passes it to the driver's registered shutdown
      interface.

  flags
      Specifies whether to register or deregister the device driver's
      shutdown interface. You can pass one of the following constants:

      DRVR_REGISTER
	      Registers a device driver shutdown interface.

      DRVR_UNREGISTER
	      Deregisters a device driver's shutdown interface.

DESCRIPTION
  The drvr_register_shutdown interface registers or deregisters a shutdown
  interface for the calling device driver. Device drivers call
  drvr_register_shutdown to register a device driver shutdown interface that
  the kernel calls at system shutdown time (or when the user halts the
  system).

  The drvr_register_shutdown interface allows device drivers to register
  interfaces that turn off the hardware device before the system shuts down.
  For example, a device driver that operates on a SCSI bus connected to two
  host CPUs (Available Server Environment) must ensure that the SCSI adapter
  on the shutdown host CPU is not doing work on the bus.





NOTES
  Device drivers should call the drvr_register_shutdown interface if it is
  necessary to call a shutdown interface that the kernel calls after it
  performs the dump operation. Device drivers should call the
  drvr_register_flush interface if it is necessary to call a flush interface
  before the kernel performs a dump operation.

CAUTIONS
  The drvr_register_shutdown interface causes a system crash and displays an
  appropriate message on the console terminal if the device driver writer
  sets an invalid bit in the flags argument.

  The shutdown interface that you register should never acquire a simple or
  complex lock. The reason for this is that on a panic, the kernel's call to
  the shutdown interface can cause the CPU to double panic, hang, or both if
  the callback interface tries to access locks that were taken through active
  code paths at the time of the panic. This double panic or hang of the CPU
  would result in no crash dump for diagnosis. A hang of the CPU can require
  operator intervention to restart the CPU.

  After the system has performed the crash dump and a panic occurs, the
  kernel's call to the shutdown interface can cause the CPU to double panic,
  hang, or both. This double panic or hang of the CPU can be the result of
  the following activities:

    ·  If the shutdown interface tries to access locks that were taken
       through active code paths at the time of the panic.

    ·  The device being shutdown exists along the hardware path that the
       crash dump used. The process of performing the crash dump gives
       control of all hardware used for the dump (devices, controllers,
       bridges, and so forth, thus the hardware path) to the console. Upon
       returning from the crash dump, anything connected to the hardware path
       might no longer function as the console has disrupted the hardware
       state expected by the kernel. A hang of the CPU can require operator
       intervention to restart the CPU.

RETURN VALUES
  None

SEE ALSO
  Kernel Interfaces: drvr_register_flush(9r)

Index for Section 9

Alphabetical listing for D

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