From a1ab34e3d0ec563a3935e7a8258ac655aac2159c Mon Sep 17 00:00:00 2001 From: Bruce Evans Date: Thu, 27 Feb 1997 18:03:48 +0000 Subject: [PATCH] Wrapped mi_switch() with splstatclock()/splx(). This fixes excessive interrupt latency for certain cases involving for restarting stopped processes. --- sys/kern/kern_synch.c | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-) diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c index 8c8a436b1d09..04339cde1f9b 100644 --- a/sys/kern/kern_synch.c +++ b/sys/kern/kern_synch.c @@ -36,7 +36,7 @@ * SUCH DAMAGE. * * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95 - * $Id$ + * $Id: kern_synch.c,v 1.29 1997/02/22 09:39:12 peter Exp $ */ #include "opt_ktrace.h" @@ -527,12 +527,31 @@ mi_switch() register struct proc *p = curproc; /* XXX */ register struct rlimit *rlim; register long s, u; + int x; struct timeval tv; + /* + * XXX this spl is almost unnecessary. It is partly to allow for + * sloppy callers that don't do it (issignal() via CURSIG() is the + * main offender). It is partly to work around a bug in the i386 + * cpu_switch() (the ipl is not preserved). We ran for years + * without it. I think there was only a interrupt latency problem. + * The main caller, tsleep(), does an splx() a couple of instructions + * after calling here. The buggy caller, issignal(), usually calls + * here at spl0() and sometimes returns at splhigh(). The process + * then runs for a little too long at splhigh(). The ipl gets fixed + * when the process returns to user mode (or earlier). + * + * It would probably be better to always call here at spl0(). Callers + * are prepared to give up control to another process, so they must + * be prepared to be interrupted. The clock stuff here may not + * actually need splstatclock(). + */ + x = splstatclock(); + #ifdef SIMPLELOCK_DEBUG - if (p->p_simple_locks) { + if (p->p_simple_locks) printf("sleep: holding simple lock"); - } #endif /* * Compute the amount of time during which the current @@ -574,6 +593,7 @@ mi_switch() cnt.v_swtch++; cpu_switch(p); microtime(&runtime); + splx(x); } /*