ddi_enter_critical(9f) [sunos 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

       ddi_enter_critical() 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 or interrupt 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 5.10							    4 Nov 1991						    ddi_enter_critical(9F)

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

NAME

       ddi_intr_hilevel - indicate interrupt handler type

SYNOPSIS

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

       int ddi_intr_hilevel(dev_info_t *dip, uint_t inumber);

INTERFACE LEVEL

       Solaris	DDI specific (Solaris DDI). This interface is obsolete. Use the new interrupt interfaces referenced in Intro(9F). Refer to Writing
       Device Drivers for more information.

PARAMETERS

       dip	  Pointer to dev_info structure.

       inumber	  Interrupt number.

DESCRIPTION

       The ddi_intr_hilevel() function returns non-zero if the specified interrupt is a "high level" interrupt.

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

       In addition, high level interrupt handlers must take care to do a minimum of work because they are not preemptable.

       A  typical  high  level	interrupt handler would put data into a circular buffer and schedule a soft interrupt by calling ddi_trigger_soft-
       intr(). The circular buffer could be protected by using a mutex that was properly initialized for the interrupt handler.

       The ddi_intr_hilevel() function can be used before calling ddi_add_intr() to decide which type of interrupt handler should  be  used.  Most
       device  drivers	are  designed  with  the  knowledge  that the devices they support will always generate low level interrupts, however some
       devices, for example those using SBus or VME bus level 6 or 7 interrupts must use this test because on some machines those  interrupts  are
       high level (above the scheduler level) and on other machines they are not.

RETURN VALUES

       non-zero    indicates a high-level interrupt.

CONTEXT

       These functions can be called from useruser, interrupt, or kernel context.

ATTRIBUTES

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

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

SEE ALSO

       ddi_add_intr(9F), Intro(9F), mutex(9F)

       Writing Device Drivers

SunOS 5.11							    16 Jan 2006 					      ddi_intr_hilevel(9F)