After the main thread in a multi-threaded program calls pthread_exit()
while other threads are still running, attempting to open files in /proc
(like /proc/mounts) fails because get_proc_task(inode)->nsproxy == NULL
(see fs/proc/base.c::mounts_open). I tested kernel 2.6.12 + glibc 2.3.5
and kernel 2.6.23 + glibc 2.6.1 with the same results. Here is a
program to illustrate:
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <pthread.h>
static void *thread_func(void *x)
{
for (;;)
{
int fd;
fd = open("/proc/mounts", O_RDONLY);
if (fd == -1)
{
perror("open /proc/mounts");
abort();
}
close(fd);
printf("/proc/mounts still accessible\n");
sleep(1);
}
return NULL;
}
int main(int argc, char *argv[])
{
pthread_t thr;
pthread_attr_t thread_attr;
pthread_attr_init(&thread_attr);
pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
pthread_create(&thr, &thread_attr, &thread_func, NULL);
sleep(5);
printf("main thread calling pthread_exit...\n");
pthread_exit(NULL);
return 0;
}
Compile with "-D_REENTRANT -lpthread". Output:
/proc/mounts still accessible
/proc/mounts still accessible
/proc/mounts still accessible
/proc/mounts still accessible
/proc/mounts still accessible
main thread calling pthread_exit...
open /proc/mounts: Invalid argument
Aborted
If it is valid for main() to call pthread_exit() while leaving other
threads running, then this is a bug. If it is not valid, then this
problem can be ignored, but let me know if that is the case. AFAIK,
everything else seems to work in this situation; problems opening files
in /proc being the only exception that I have encountered so far.
Thanks,
Tony Battersby
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