Date: Thu, 29 Apr 1999 16:14:09 -0500 (CDT) From: Kevin Day <toasty@home.dragondata.com> To: hackers@freebsd.org Subject: mmaping /dev/mem then spawning children Message-ID: <199904292114.QAA00336@home.dragondata.com>
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I'm completely at a loss as to why this happens, but it just sprang up when
we upgraded from 3.0-RELEASE to 3.1-RELEASE.
I have a process that mmap's a device. (Our own custom driver). It then
spawns some children that don't really need access to it. However,
top/ps/etc show that the child is eating 32760 megabytes of ram.
This also seems to happen if you mmap /dev/mem, or a few other devices. Am I
just doing something stupid here, or is this an honest bug?
Here's sample code to reproduce this. Compile them both, then run '1'.
1.c:
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/errno.h>
#include <sys/types.h>
#include <sys/mman.h>
void main(void) {
int k;
char *low;
int devmem;
devmem = open("/dev/mem",O_RDWR);
low1mb = (char *)mmap(0, 0x800000, (PROT_READ | PROT_WRITE), MAP_INHERIT | MAP_SHARED, devmem, 0);
printf("Starting 2...\n");
if (rfork(RFCFDG|RFPROC)) {
usleep(100);
} else {
k = execl("./2", "2", (char *) 0);
if (k) {
printf("io returned %d errno %d\n",k, errno);
}
_exit(0);
}
}
2.c:
void main(void) {
while(1)
sleep(10000);
}
I run ./1
top shows:
PID USERNAME PRI NICE SIZE RES STATE TIME WCPU CPU COMMAND
899 root 10 0 748K 32760M nanslp 0:00 0.00% 0.00% 2
ps shows:
root 899 0.0 53622.9 748 -7960 p1 I 6:14AM 0:00.00 2 0 899 1 0 10 0 748 -7960 nanslp I p1 0:00.00 2
-7960k.... which is about 8M (from the mmap) minus how much '2' should really be taking up.
Is this a real bug?
Kevin
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