ddi_enter_critical(9f) [opensolaris man page]

ddi_enter_critical(9F)					   Kernel Functions for Drivers 				    ddi_enter_critical(9F)

NAME

       ddi_enter_critical, ddi_exit_critical - enter and exit a critical region of control

SYNOPSIS

       #include <sys/conf.h>
       #include <sys/ddi.h>
       #include <sys/sunddi.h>

       unsigned int ddi_enter_critical(void);

       void ddi_exit_critical(unsignedint ddic);

INTERFACE LEVEL

       Solaris DDI specific (Solaris DDI).

PARAMETERS

       ddic    The returned value from the call to ddi_enter_critical() must be passed to ddi_exit_critical().

DESCRIPTION

       Nearly  all driver operations can be done without any special synchronization and protection mechanisms beyond those provided by, for exam-
       ple, mutexes (see mutex(9F)). However, for certain devices there can exist a very short critical region of code which must  be  allowed	to
       run  uninterrupted. The function ddi_enter_critical() provides a mechanism by which a driver can ask the system to guarantee to the best of
       its ability that the current thread of execution will neither be preempted nor interrupted. This stays in effect until a bracketing call to
       ddi_exit_critical() is made (with an argument which was the returned value from ddi_enter_critical()).

       The  driver  may  not  call  any  functions  external  to  itself  in  between the time it calls ddi_enter_critical() and the time it calls
       ddi_exit_critical().

RETURN VALUES

       The ddi_enter_critical() function returns an opaque unsigned integer which must be used in the subsequent call to ddi_exit_critical().

CONTEXT

       This function can be called from user, interrupt, or kernel context.

WARNINGS

       Driver writers should note that in a multiple processor system  this function does not temporarily suspend other processors from executing.
       This  function  also cannot guarantee to actually block the hardware from doing such things as interrupt acknowledge cycles. What it can do
       is guarantee that the currently executing thread will not be preempted.

       Do not write code  bracketed by ddi_enter_critical() and ddi_exit_critical() that can get caught in an infinite loop, as  the  machine  may
       crash if you do.

SEE ALSO

       mutex(9F)

       Writing Device Drivers

SunOS 5.11							    16 Jan 2006 					    ddi_enter_critical(9F)

ddi_intr_get_hilevel_pri(9F)				   Kernel Functions for Drivers 			      ddi_intr_get_hilevel_pri(9F)

NAME

       ddi_intr_get_hilevel_pri - get minimum priority level for a high-level interrupt

SYNOPSIS

       #include <sys/types.h>
       #include <sys/conf.h>
       #include <sys/ddi.h>
       #include <sys/sunddi.h>

       int ddi_intr_get_hilevel_pri(void);

INTERFACE LEVEL

       Solaris DDI specific (Solaris DDI).

DESCRIPTION

       Upon a successful return, the ddi_intr_get_hilevel_pri() function returns the minimum priority level for a high-level interrupt. The return
       priority value can be used to compare to other priority values, such as those returned from ddi_intr_get_pri(9F), to determine if  a  given
       interrupt priority is a high-level interrupt.

       High-level  interrupts  must be handled without using system services that manipulate thread or process states, because such interrupts are
       not blocked by the scheduler.

       In addition, high-level interrupt handlers must take care to do a minimum of work because they cannot be preempted.

       A typical high-level interrupt handler puts data into a circular buffer and schedule a soft  interrupt  by  calling  ddi_intr_trigger_soft-
       int(). The circular buffer can be protected by using a mutex that is properly initialized for the interrupt handler.

       The ddi_intr_get_hilevel_pri() function can be used before calling ddi_intr_add_handler() to help determine which type of interrupt handler
       can be used. Most device drivers are designed with the knowledge that supported devices always  generate  low  level  interrupts.  On  some
       machines,  however,  interrupts	are  high-level  above the scheduler level and on other machines they are not. Devices such as those those
       using SBus interrupts or VME bus level 6 or 7 interrupts must use the ddi_intr_get_hilevel_pri() function to test  the  type  of  interrupt
       handler that can be used.

RETURN VALUES

       The ddi_intr_get_hilevel_pri() function returns the priority value for a high-level interrupt.

CONTEXT

       The ddi_intr_get_hilevel_pri() function can be called from either user or kernel non-interrupt context.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+

SEE ALSO

       attributes(5),	ddi_intr_add_handler(9F),  ddi_intr_alloc(9F),	ddi_intr_enable(9F),  ddi_intr_get_pri(9F),  ddi_intr_trigger_softint(9F),
       mutex(9F)

       Writing Device Drivers

SunOS 5.11							    07 Apr 2005 				      ddi_intr_get_hilevel_pri(9F)