linux-kernel - Re: [PATCH v7 3.2-rc2 3/30] uprobes: register/unregister probes.

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Date:	Wed, 23 Nov 2011 17:22:36 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-mm <linux-mm@...ck.org>, Ingo Molnar <mingo@...e.hu>,
	Andi Kleen <andi@...stfloor.org>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Roland McGrath <roland@...k.frob.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Anton Arapov <anton@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Stephen Wilson <wilsons@...rt.ca>
Subject: Re: [PATCH v7 3.2-rc2 3/30] uprobes: register/unregister probes.

On Fri, 2011-11-18 at 16:37 +0530, Srikar Dronamraju wrote:
> +int register_uprobe(struct inode *inode, loff_t offset,
> +                               struct uprobe_consumer *consumer)
> +{
> +       struct uprobe *uprobe;
> +       int ret = -EINVAL;
> +
> +       if (!consumer || consumer->next)
> +               return ret;
> +
> +       inode = igrab(inode);

So why are you dealing with !consumer but not with !inode? and why does
it make sense to allow !consumer at all?

> +       if (!inode)
> +               return ret;
> +
> +       if (offset > i_size_read(inode))
> +               goto reg_out;
> +
> +       ret = 0;
> +       mutex_lock(uprobes_hash(inode));
> +       uprobe = alloc_uprobe(inode, offset);
> +       if (uprobe && !add_consumer(uprobe, consumer)) {
> +               ret = __register_uprobe(inode, offset, uprobe);
> +               if (ret) {
> +                       uprobe->consumers = NULL;
> +                       __unregister_uprobe(inode, offset, uprobe);
> +               }
> +       }
> +
> +       mutex_unlock(uprobes_hash(inode));
> +       put_uprobe(uprobe);
> +
> +reg_out:
> +       iput(inode);
> +       return ret;
> +} 

So if this function returns an error the caller is responsible for
cleaning up consumer, otherwise we take responsibility.
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