[PATCH] c/r: make ckpt_debug() safe if called by dead tasks

[Serge E. Hallyn]

Quoting Oren Laadan (orenl at librato.com):
> From: Oren Laadan <orenl at cs.columbia.edu>
> 
> One may not call task_pid_vnr() on dead tasks because they don't have
> a valid ->nxproxy pointer. However, the ckpt_ctx cleanup may be called
> by a dead task from do_exit(), in the case of zombie or "ghost" tasks.
> 
> This patch makes ckpt_debug() safe to call from dead tasks context, so
> that debug printing from code called by ckpt_ctx_free() is cool.
> 
> Signed-off-by: Oren Laadan <orenl at cs.columbia.edu>

Acked-by: Serge Hallyn <serue at us.ibm.com>

thanks,
-serge

> ---
>  include/linux/checkpoint.h |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
> index e00dd70..5294a96 100644
> --- a/include/linux/checkpoint.h
> +++ b/include/linux/checkpoint.h
> @@ -334,7 +334,9 @@ extern unsigned long ckpt_debug_level;
>  	do {								\
>  		if (ckpt_debug_level & (level))				\
>  			printk(KERN_DEBUG "[%d:%d:c/r:%s:%d] " fmt,	\
> -				current->pid, task_pid_vnr(current),	\
> +				current->pid,				\
> +				current->nsproxy ?			\
> +				task_pid_vnr(current) : -1,		\
>  				__func__, __LINE__, ## args);		\
>  	} while (0)
> 
> -- 
> 1.6.0.4
> 
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