linux-kernel - Re: [PATCH] irq: tsk->comm is an array

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Message-ID: <alpine.DEB.2.00.1210251300140.17938@chino.kir.corp.google.com>
Date:	Thu, 25 Oct 2012 13:04:05 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] irq: tsk->comm is an array

On Thu, 25 Oct 2012, Alan Cox wrote:

> From: Alan Cox <alan@...ux.intel.com>
> 
> More relevantly what about termination and locks ?
> 

The string is always properly terminated with a trailing zero no matter 
how it is written.  For threads other than current, the locking is 
task_lock(task); for current, there are hundreds of places without locking 
and it is generally considered acceptable for a race to print a mangled 
string from a concurrent write to /proc/pid/comm.

> Anyway the array check is useless so remove it.
> 
> Signed-off-by: Alan Cox <alan@...ux.intel.com>
> ---
> 
>  kernel/irq/manage.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index 4c69326..ea39714 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -792,8 +792,9 @@ static void irq_thread_dtor(struct callback_head *unused)
>  
>  	action = kthread_data(tsk);
>  
> +	/* FIXME: locking */
>  	pr_err("exiting task \"%s\" (%d) is an active IRQ thread (irq %d)\n",
> -	       tsk->comm ? tsk->comm : "", tsk->pid, action->irq);
> +	       tsk->comm, tsk->pid, action->irq);

Ack without the comment, no locking necessary.

>  
>  
>  	desc = irq_to_desc(action->irq);
--
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