KPREEMPT(9)						   BSD Kernel Developer's Manual					       KPREEMPT(9)

NAME

     kpreempt -- control kernel preemption

SYNOPSIS

     #include <sys/systm.h>

     void
     kpreempt_disable(void);

     void
     kpreempt_enable(void);

     bool
     kpreempt_disabled(void);

DESCRIPTION

     These functions are used to control kernel preemption of the calling LWP.

     On architectures where kernel preemption is not supported natively, these functions may still be used.

     It should be noted that kernel preemption is also disabled when holding the interrupt priority level above IPL_NONE, e.g. using spl(9) or
     spinning mutex(9) calls or holding kernel_lock (indicating that the code is not MT safe).

     kpreempt_disable() disables kernel preemption of the calling LWP.	Note that disabling kernel preemption can prevent LWPs with higher priori-
     ties from running.

     kpreempt_enable() enables kernel preemption of the calling LWP, which was previously disabled by kpreempt_disable().

     kpreempt_disable() and kpreempt_enable() can be nested.

     kpreempt_disabled() returns true if preemption of the calling LWP is disabled.  It is only for diagnostic purpose.

SEE ALSO

     intro(9), mutex(9), spl(9)

BSD
								 February 16, 2010							       BSD