[src/trunk]: src/sys/arch/powerpc/powerpc propagate the MP idle-loop fix to p...

[chs <chs%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/2b2b69bea24a
branches:  trunk
changeset: 534489:2b2b69bea24a
user:      chs <chs%NetBSD.org@localhost>
date:      Sun Jul 28 07:05:06 2002 +0000

description:
propagate the MP idle-loop fix to ppc from the other ports:

  Move call to sched_unlock_idle to later in the context switch to
  eliminate a race where another processor could grab the outgoing
  process before we were done saving our state into it, with predictable
  results.

  Bug spotted by Frank van der Linden <fvdl%wasabisystems.com@localhost>

also, don't re-enable interrupts temporarily in the middle of
switching to a new process, just wait until we're completely switched.
this didn't work on MP and it's not worth the effort.

diffstat:

 sys/arch/powerpc/powerpc/locore_subr.S |  50 ++++++++-------------------------
 1 files changed, 13 insertions(+), 37 deletions(-)

diffs (118 lines):

diff -r b724fdf658b2 -r 2b2b69bea24a sys/arch/powerpc/powerpc/locore_subr.S
--- a/sys/arch/powerpc/powerpc/locore_subr.S    Sun Jul 28 07:03:47 2002 +0000
+++ b/sys/arch/powerpc/powerpc/locore_subr.S    Sun Jul 28 07:05:06 2002 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: locore_subr.S,v 1.4 2002/07/16 23:04:21 matt Exp $     */
+/*     $NetBSD: locore_subr.S,v 1.5 2002/07/28 07:05:06 chs Exp $      */
 
 /*
  * Copyright (C) 1995, 1996 Wolfgang Solfrank.
@@ -79,7 +79,6 @@
        andi.   3,3,~PSL_EE@l           /* disable interrupts while
                                           manipulating runque */
        mtmsr   3
-
 #if defined(MULTIPROCESSOR) || defined(LOCKDEBUG)
        bl      _C_LABEL(sched_lock_idle)
 #endif
@@ -118,8 +117,7 @@
  * void cpu_switch(struct proc *p)
  * Find a runnable process and switch to it.
  */
-/* XXX noprofile?  --thorpej%netbsd.org@localhost */
-ENTRY(cpu_switch)
+ENTRY_NOPROFILE(cpu_switch)
        mflr    0                       /* save lr */
        stw     0,4(1)
        stwu    1,-16(1)
@@ -164,7 +162,7 @@
        bl      _C_LABEL(sched_unlock_idle)
 #endif
 
-       xor     3,3,3
+       xor     3,3,3                   /* spl0() */
        bl      _C_LABEL(lcsplx)
 #if !defined(MULTIPROCESSOR)
        stw     3,PCB_SPL(31)           /* save spl */
@@ -219,11 +217,6 @@
 
        stw     3,P_BACK(31)            /* probably superfluous */
 
-#if defined(MULTIPROCESSOR) || defined(LOCKDEBUG)
-       /* Unlock the sched_lock, but leave interrupts off, for now. */
-       bl      _C_LABEL(sched_unlock_idle)
-#endif
-
 #if defined(MULTIPROCESSOR)
        GET_CPUINFO(4)
        stw     4,P_CPU(31)             /* p->p_cpu = curcpu() */
@@ -242,10 +235,6 @@
 #endif
        lwz     4,P_ADDR(31)
 
-       mfmsr   3
-       ori     3,3,PSL_EE@l            /* Now we can interrupt again */
-       mtmsr   3
-
 #if !defined(MULTIPROCESSOR)           /* XXX */
        cmpl    0,31,30                 /* is it the same process? */
        beq     switch_return
@@ -260,13 +249,9 @@
        stmw    10,8(1)
        lwz     3,P_ADDR(30)
        stw     1,PCB_SP(3)             /* save SP */
-#endif
 
 switch_exited:
-       mfmsr   3
-       andi.   3,3,~PSL_EE@l           /* disable interrupts while
-                                          actually switching */
-       mtmsr   3
+#endif
 
        /* indicate new pcb */
 #if defined(MULTIPROCESSOR)
@@ -286,27 +271,9 @@
        stwu    5,_C_LABEL(curpm)@l(6)
 #endif
        stwcx.  5,0,6                   /* clear possible reservation */
-
-#if 0
-       addic.  5,5,64
-       li      6,0
-       mfsr    8,KERNEL_SR             /* save kernel SR */
-1:
-       addis   6,6,-0x10000000@ha      /* set new procs segment registers */
-       or.     6,6,6                   /* This is done from the real
-                                          address pmap */
-       lwzu    7,-4(5)                 /* so we don't have to worry */
-       mtsrin  7,6                     /* about accessibility */
-       bne     1b
-       mtsr    KERNEL_SR,8             /* restore kernel SR */
-#endif
        isync
 
        lwz     1,PCB_SP(4)             /* get new procs SP */
-
-       ori     3,3,PSL_EE@l            /* interrupts are okay again */
-       mtmsr   3
-
        lmw     10,8(1)                 /* get other regs */
        lwz     1,0(1)                  /* get saved SP */
        mr      2,12                    /* get saved r2 */
@@ -316,6 +283,15 @@
        isync
 
 switch_return:
+#if defined(MULTIPROCESSOR) || defined(LOCKDEBUG)
+       /* Unlock the sched_lock, but leave interrupts off, for now. */
+       bl      _C_LABEL(sched_unlock_idle)
+#endif
+
+       mfmsr   3
+       ori     3,3,PSL_EE@l            /* interrupts are okay again */
+       mtmsr   3
+
        mr      30,7                    /* save proc pointer */
        lwz     3,PCB_SPL(4)
        bl      _C_LABEL(lcsplx)