ras(9) - NetBSD Manual Pages

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RAS(9)                 NetBSD Kernel Developer's Manual                 RAS(9)

ras_lookup, ras_fork, ras_purgeall -- restartable atomic sequences
#include <sys/types.h> #include <sys/proc.h> #include <sys/ras.h> void * ras_lookup(struct proc *p, void *addr); int ras_fork(struct proc *p1, struct proc *p2); int ras_purgeall(struct proc *p);
Restartable 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 during cpu_switch(9). If a process is found to have been preempted during a restartable sequence, then its execution is rolled-back to the start of the sequence by resetting its program counter saved in its process con- trol block (PCB). The RAS functionality is provided by a combination of the machine-inde- pendent routines discussed in this page and a machine-dependent component in cpu_switch(9). A port which supports restartable atomic sequences will define __HAVE_RAS in machine/types.h for machine-independent code to conditionally provide RAS support. A complicated side-effect of restartable atomic sequences is their inter- action with the machine-dependent ptrace(2) support. Specifically, sin- gle-step traps and/or the emulation of single-stepping must carefully consider the effect on restartable atomic sequences. A general solution is to ignore these traps or disable them within restartable atomic sequences.
The functions which operate on restartable atomic sequences are: ras_lookup(p, addr) This function searches the registered restartable atomic sequences for process p which contain the user address addr. If the address addr is found within a RAS, then the restart address of the 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 process p2. It is primarily called from fork1(9) when the sequences are inherited from the parent by the child. ras_purgeall(p) This function is used to remove all registered restartable atomic sequences for process p. It is primarily used to remove all registered restartable atomic sequences for a process during exec(3) and by rasctl(2).
This section describes places within the NetBSD source tree where actual code implementing or using the RAS functionality can be found. All path- names are relative to /usr/src. The RAS framework itself is implemented within the file sys/kern/kern_ras.c. Data structures and function prototypes for the framework are located in sys/sys/ras.h. Machine-dependent portions are implemented within cpu_switch(9) in the machine-dependent file sys/arch/<arch>/<arch>/locore.S.
rasctl(2), cpu_switch(9), fork1(9)
The RAS functionality first appeared in NetBSD 2.0. NetBSD 5.0 August 12, 2002 NetBSD 5.0
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