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Date: Fri, 31 Jul 2009 23:52:23 +0200
From: cinap_lenrek@gmx.de
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Subject: Re: [9fans] Race condition in /sys/src/9/pc/trap.c?
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i attached it in a previous mail... try again...

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From: erik quanstrom <quanstro@coraid.com>
Date: Fri, 31 Jul 2009 14:00:25 -0400
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Subject: Re: [9fans] Race condition in /sys/src/9/pc/trap.c?
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> process1:
> 	still in kernel:
> 		memmove(buf, ...)
> 		*fault*
> 		trap()
> 			fault386()
> 				fault() => -1
> 				if(!user){
> 					panic()
> 					*panic*
> 				}
> 				...
> 				postnote()

could you be more specific.  what is your test program,
where is it crashing (if you know), and what is the panic
message, if any?  i must be dense, but i'm confused by
your process diagram.

- erik
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#include <u.h>
#include <libc.h>

void
main(int argc, char **argv)
{
	char *buf;
	int fd;

	if((fd = open("/dev/zero", OREAD)) < 0)
		sysfatal("open");

	buf = (char*)0x600000;
	segattach(0, "memory", buf, 2*4096);

	switch(rfork(RFPROC|RFMEM)){
	case -1:
		sysfatal("fork");
		break;
	case 0:
		for(;;){
			read(fd, buf+4096, 4096);
		}
	}
	sleep(1000);
	segbrk(buf, buf+4096);
}

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