linux-kernel - Re: [patch 7/9] signals: Fix more rcu assumptions

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Message-ID: <13656.1260539944@redhat.com>
Date:	Fri, 11 Dec 2009 13:59:04 +0000
From:	David Howells <dhowells@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	dhowells@...hat.com, Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	James Morris <jmorris@...ei.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [patch 7/9] signals: Fix more rcu assumptions

Thomas Gleixner <tglx@...utronix.de> wrote:

> > Perhaps it is better to modify __sigqueue_alloc() instead? It can take
> > rcu_lock() around cred->user itself.
> 
> Indeed. Was too tired to see the obvious :)

Ah, but...  If __sigqueue_alloc() is called from sigqueue_alloc(), then you
don't need the RCU read lock as the target task is current.

So perhaps the callsite for __sigqueue_alloc() in __send_signal()?  That at
least puts the rcu_read_lock() call in proximity to the function that actually
needs it.

David
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