INTRO (9) NetBSD Kernel Developer's Manual INTRO (9) NAME ...

RAS (9) NetBSD Kernel Developer’s Manual RAS (9)NAMEras_lookup, ras_fork, ras_purgeall —restartable atomic sequencesSYNOPSIS#include #include #include void ∗ras_lookup(struct proc ∗p , void ∗addr);intras_fork(struct proc ∗p1 , struct proc ∗p2);intras_purgeall(struct proc ∗p);DESCRIPTIONRestartable atomic sequences are user code sequences which are guaranteed to execute without preemption.This property is assured by checking the set of restartable atomic sequences registered for a process duringcpu_switch(9). If aprocess is found to have been preempted during a restartable sequence, then itsexecution is rolled-back to the start of the sequence by resetting its program counter saved inits process controlblock (PCB).The RAS functionality is provided by a combination of the machine-independent routines discussed in thispage and a machine-dependent component in cpu_switch(9). A port which supports restartable atomicsequences will define __HAVE_RAS in machine/types.h for machine-independent code to conditionallyprovide RAS support.Acomplicated side-effect of restartable atomic sequences is their interaction with the machine-dependentptrace(2) support. Specifically, single-step traps and/or the emulation of single-stepping must carefullyconsider the effect on restartable atomic sequences. Ageneral solution is to ignore these traps or disablethem within restartable atomic sequences.FUNCTIONSThe functions which operate on restartable atomic sequences are:ras_lookup(p , addr)This function searches the registered restartable atomic sequences for process p which containthe user address addr. Ifthe address addr is found within a RAS, then the restart address ofthe RAS is returned, otherwise −1 is returned.ras_fork(p1 , p2)This function is used to copy all registered restartable atomic sequences for process p1 to processp2. Itisprimarily called from fork1(9) when the sequences are inherited from the parent bythe child.ras_purgeall(p)This function is used to remove all registered restartable atomic sequences for process p. Itisprimarily used to remove all registered restartable atomic sequences for a process duringexec(3) and by rasctl(2).CODE REFERENCESThis section describes places within the NetBSD source tree where actual code implementing or using theRAS functionality can be found. All pathnames are relative to /usr/src.NetBSD 3.0 August 12, 2002 1