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Wrapped mi_switch() with splstatclock()/splx(). This fixes excessive

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interrupt latency for certain cases involving for restarting stopped
processes.
This commit is contained in:
Bruce Evans 1997-02-27 18:03:48 +00:00
parent 886ee0aa9f
commit a1ab34e3d0
1 changed files with 23 additions and 3 deletions
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26
sys/kern/kern_synch.c
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@ -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);
}
/*