[lxc-devel] [PATCH 2/2] Support stopping containers concurrently

[Stéphane Graber]

On 04/23/2013 05:29 AM, S.Çağlar Onur wrote:
> Hey Stéphane,
> 
> On Wed, Apr 17, 2013 at 6:06 PM, Serge Hallyn <serge.hallyn at ubuntu.com
> <mailto:serge.hallyn at ubuntu.com>> wrote:
> 
>     Quoting S.Çağlar Onur (caglar at 10ur.org <mailto:caglar at 10ur.org>):
>     > From: "S.Çağlar Onur" <caglar at 10ur.org <mailto:caglar at 10ur.org>>
>     >
>     > Trying to stop multiple containers concurrently ends up with
>     "cgroup is not mounted" errors as multiple threads corrupts the
>     shared variables.
>     > Fix that stack corruption and start to use getmntent_r to support
>     stopping multiple containers concurrently.
>     >
>     > Signed-off-by: S.Çağlar Onur <caglar at 10ur.org
>     <mailto:caglar at 10ur.org>>
>     > ---
>     >  src/lxc/cgroup.c  |  152
>     +++++++++++++++++++++++++++++++++++------------------
>     >  src/lxc/freezer.c |   18 +++++--
>     >  src/lxc/state.c   |   15 ++++--
>     >  3 files changed, 126 insertions(+), 59 deletions(-)
>     >
>     > diff --git a/src/lxc/cgroup.c b/src/lxc/cgroup.c
>     > index 368214f..0739477 100644
>     > --- a/src/lxc/cgroup.c
>     > +++ b/src/lxc/cgroup.c
>     > @@ -54,6 +54,11 @@ lxc_log_define(lxc_cgroup, lxc);
>     >
>     >  #define MTAB "/proc/mounts"
>     >
>     > +/* In the case of a bind mount, there could be two long pathnames
>     in the
>     > + * mntent plus options so use large enough buffer size
>     > + */
>     > +#define LARGE_MAXPATHLEN 4 * MAXPATHLEN
>     > +
>     >  /* Check if a mount is a cgroup hierarchy for any subsystem.
>     >   * Return the first subsystem found (or NULL if none).
>     >   */
>     > @@ -100,29 +105,31 @@ static char *mount_has_subsystem(const
>     struct mntent *mntent)
>     >   */
>     >  static int get_cgroup_mount(const char *subsystem, char *mnt)
>     >  {
>     > -     struct mntent *mntent;
>     > +     struct mntent *mntent, mntent_r;
>     >       FILE *file = NULL;
>     >       int ret, err = -1;
>     >
>     > +     char buf[LARGE_MAXPATHLEN] = {0};
> 
>     Ah yes, this must be what I thought we were waiting on - a response
>     from Stéphane on this.
> 
>     I'm still worried about this stack usage, especially in something
>     which is rather commonly called.  Stéphane, is this a non-issue
>     for arm?

So I had a quick look on an Android device. The stack size is the same
as a desktop machine (8192KB), so the 16KB used by that variable won't
be a problem.

> 
> 
> Have you had a chance to look at that? Should I keep them like this or
> start to allocate them via calloc?
> 
> 
>     -serge
> 
> 
> 
> Cheers,
> -- 
> S.Çağlar Onur <caglar at 10ur.org <mailto:caglar at 10ur.org>>


-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com

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