[9fans] disabling swap

["Steve Simon" <steve@quintile.net>]

I have just hit a fossil deadlock. the symptom is simple enough,
fossil wedged, stats continued to be updated and I could run whatis
in a rio window but any attempt to access the local fossil caused
the command to hang.

I was trying to mirror sources when it happened so I had a lot of
processes all writing to fossil at the same time - well, perhaps a dozen.

If anyone is interested I have put my 9pccpuf and a phone camera
image of ^t^t^p of the hang in http://www.quintile.net/doorstep/deadlock.jpg
and http://www.quintile.net/doorstep/9pccpuf.

If anyone extracts info from this I would like to learn how they do it.

I made a feeble attempt to diagnose the problem myself (below) and it looks
as though it was trying to swap, however, though I do have a /dev/sdXX/swap
I believe I have disabled the one place where swap is enabled (/cfg/$sysname/cpurc).

having said this I think /dev/mem is indicating that I _do_ have swap enabled. either
way I should not have been swapping as I have masses of free RAM.

-Steve (confused)


cpu% acid /386/9pccpuf
/386/9pccpuf:386 plan 9 boot image
/sys/lib/acid/port
/sys/lib/acid/386
acid: src(0xf01d3968)
/sys/src/9/port/fault.c:231
 226		k = kmap(new);
 227		kaddr = (char*)VA(k);
 228
 229		if(loadrec == 0) {			/* This is demand load */
 230			c = s->image->c;
>231			while(waserror()) {
 232				if(strcmp(up->errstr, Eintr) == 0)
 233					continue;
 234				kunmap(k);
 235				putpage(new);
 236				faulterror("sys: demand load I/O error", c, 0);
acid: src(0xf01d730f)
/sys/src/9/port/proc.c:576
 571		/* Only reliable way to see if we are Running */
 572		if(p->mach == 0) {
 573			p->newtlb = 1;
 574			ok = 1;
 575		}
>576		unlock(runq);
 577		spllo();
 578
 579		return ok;
 580	}
 581
acid:
cpu%

cpu% cat /dev/swap
2134908928 memory
4096 pagesize
27037 kernel
112466/494181 user
0/160000 swap
4588640/71348716 kernel malloc
0/16777216 kernel draw

cpu% grep swap /cfg/$sysname/cpurc
# swap is broken
# swap `{ls /dev/fs/swap /dev/sd*/swap >[2] /dev/null | sed 1q}