linux-kernel - Re: [PATCH v5 3.1.0-rc4-tip 3/26] Uprobes: register/unregister probes.

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Message-ID: <20111007170347.GB32319@redhat.com>
Date:	Fri, 7 Oct 2011 19:03:47 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>,
	Hugh Dickins <hughd@...gle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v5 3.1.0-rc4-tip 3/26]   Uprobes: register/unregister
	probes.

On 10/06, Srikar Dronamraju wrote:
>
> * Oleg Nesterov <oleg@...hat.com> [2011-10-05 20:50:08]:
>
> yes we might be doing an unnecessary __register_uprobe() but because it
> raced with unregister_uprobe() and got the lock, we would avoid doing a
> __unregister_uprobe().
>
> However I am okay to move the lock before del_consumer().

To me this looks a bit "safer" even if currently __register is idempotent.

But,

> Please let me
> know how you prefer this.

No, no, Srikar. Please do what you prefer. You are the author.

And btw I forgot to mention that initially I wrongly thought this is buggy.

Oleg.

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