[lxc-devel] [PATCH 1/1] api_start: refuse to run undaemonized if multithreaded

[Stéphane Graber]

On Thu, Nov 07, 2013 at 10:20:33PM -0600, Serge Hallyn wrote:
> lxc-start is not safe (and doesn't actually make sense) if the
> task is nto single-threaded.
> 
> Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>

Acked-by: Stéphane Graber <stgraber at ubuntu.com>

> ---
>  src/lxc/lxccontainer.c | 37 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 
> diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
> index 05e5405..827cae0 100644
> --- a/src/lxc/lxccontainer.c
> +++ b/src/lxc/lxccontainer.c
> @@ -506,6 +506,38 @@ static bool wait_on_daemonized_start(struct lxc_container *c)
>  	return lxcapi_wait(c, "RUNNING", timeout);
>  }
>  
> +static bool am_single_threaded(void)
> +{
> +	struct dirent dirent, *direntp;
> +	DIR *dir;
> +	int count=0;
> +
> +	process_lock();
> +	dir = opendir("/proc/self/task");
> +	process_unlock();
> +	if (!dir) {
> +		INFO("failed to open /proc/self/task");
> +		return false;
> +	}
> +
> +	while (!readdir_r(dir, &dirent, &direntp)) {
> +		if (!direntp)
> +			break;
> +
> +		if (!strcmp(direntp->d_name, "."))
> +			continue;
> +
> +		if (!strcmp(direntp->d_name, ".."))
> +			continue;
> +		if (++count > 1)
> +			break;
> +	}
> +	process_lock();
> +	closedir(dir);
> +	process_unlock();
> +	return count == 1;
> +}
> +
>  /*
>   * I can't decide if it'd be more convenient for callers if we accept '...',
>   * or a null-terminated array (i.e. execl vs execv)
> @@ -598,6 +630,11 @@ static bool lxcapi_start(struct lxc_container *c, int useinit, char * const argv
>  		open("/dev/null", O_RDWR);
>  		open("/dev/null", O_RDWR);
>  		setsid();
> +	} else {
> +		if (!am_single_threaded()) {
> +			ERROR("Cannot start non-daemonized container when threaded");
> +			return false;
> +		}
>  	}
>  
>  reboot:
> -- 
> 1.8.3.2
> 
> 
> ------------------------------------------------------------------------------
> November Webinars for C, C++, Fortran Developers
> Accelerate application performance with scalable programming models. Explore
> techniques for threading, error checking, porting, and tuning. Get the most 
> from the latest Intel processors and coprocessors. See abstracts and register
> http://pubads.g.doubleclick.net/gampad/clk?id=60136231&iu=/4140/ostg.clktrk
> _______________________________________________
> Lxc-devel mailing list
> Lxc-devel at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/lxc-devel

-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 836 bytes
Desc: Digital signature
URL: <http://lists.linuxcontainers.org/pipermail/lxc-devel/attachments/20131108/977f87fc/attachment.pgp>