CVS commit: src/sys/arch/arm

[Steve Woodford <scw%netbsd.org@localhost>]

Module Name:    src
Committed By:   scw
Date:           Thu Oct 23 08:59:10 UTC 2003

Modified Files:
        src/sys/arch/arm/arm32: cpuswitch.S vm_machdep.c
        src/sys/arch/arm/include/arm32: frame.h

Log Message:
Don't drop to spl0 in cpu_switch/cpu_switchto. Do it in the idle loop
instead.

With this change, we no longer need to save the current interrupt level
in the switchframe. This is no great loss since both cpu_switch and
cpu_switchto are always called at splsched, so the process' spl is
effectively saved somewhere in the callstack.

This fixes an evbarm problem reported by Allen Briggs:

        lwp gets into sa_switch -> mi_switch with newl != NULL
            when it's the last element on the runqueue, so it
            hits the second bit of:
                if (newl == NULL) {
                        retval = cpu_switch(l, NULL);
                } else {
                        remrunqueue(newl);
                        cpu_switchto(l, newl);
                        retval = 0;
                }

        mi_switch calls remrunqueue() and cpu_switchto()

        cpu_switchto unlocks the sched lock
        cpu_switchto drops CPU priority
        softclock is received
        schedcpu is called from softclock
        schedcpu hits the first if () {} block here:
                if (l->l_priority >= PUSER) {
                        if (l->l_stat == LSRUN &&
                            (l->l_flag & L_INMEM) &&
                            (l->l_priority / PPQ) != (l->l_usrpri / PPQ)) {
                                remrunqueue(l);
                                l->l_priority = l->l_usrpri;
                                setrunqueue(l);
                        } else
                                l->l_priority = l->l_usrpri;
                }

        Since mi_switch has already run remrunqueue, the LWP has been
            removed, but it's not been put back on any queue, so the
            remrunqueue panics.


To generate a diff of this commit:
cvs rdiff -r1.37 -r1.38 src/sys/arch/arm/arm32/cpuswitch.S
cvs rdiff -r1.29 -r1.30 src/sys/arch/arm/arm32/vm_machdep.c
cvs rdiff -r1.5 -r1.6 src/sys/arch/arm/include/arm32/frame.h

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.