lkml.org 
[lkml]   [2009]   [Feb]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [cgroup or VFS ?] WARNING: at fs/namespace.c:636 mntput_no_expire+0xac/0xf2()
On Thu, Feb 12, 2009 at 02:54:58PM +0800, Li Zefan wrote:
> But the following testcase can also trigger the warning:
>
> thread 1:
> for ((; ;))
> {
> mount -t cgroup -o ns xxx cgroup/ > /dev/null 2>&1
> # remove the dirs generated by cgroup_clone()
> rmdir cgroup/[1-9]* > /dev/null 2>&1
> umount cgroup/ > /dev/null 2>&1
> }
>
>
> thread 2:
>
> int foo(void *arg)
> { return 0; }
>
> char *stack[4096];
>
> int main(int argc, char **argv)
> {
> int usec = DEFAULT_USEC;
> while (1) {
> usleep(usec);
> # cgroup_clone() will be called
> clone(foo, stack+4096, CLONE_NEWNS, NULL);
> }
>
> return 0;
> }

Uh-oh... That clone() will do more, actually - it will clone a bunch
of vfsmounts. What happens if you create a separate namespace for the
first thread, so that the second one would not have our vfsmount to
play with?

Alternatively, what if the second thread is doing
mount --bind cgroup foo
umount foo
in a loop?

Another one: does turning the umount in the first thread into umount -l
affect anything?


\
 
 \ /
  Last update: 2009-02-12 08:11    [from the cache]
©2003-2011 Jasper Spaans