linux-kernel - Re: [PATCH v5 3.1.0-rc4-tip 26/26] uprobes: queue signals while thread is singlestepping.

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Message-ID: <20111007165828.GA32319@redhat.com>
Date:	Fri, 7 Oct 2011 18:58:28 +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>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Hugh Dickins <hughd@...gle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jonathan Corbet <corbet@....net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 3.1.0-rc4-tip 26/26]   uprobes: queue signals while
	thread is singlestepping.

On 10/06, Srikar Dronamraju wrote:
>
> The patch (that I sent out as part of v5 patchset) uses per task
> pending sigqueue and start queueing the signals when the task
> singlesteps. After completion of singlestep, walks thro the pending
> signals.

Yes, I see. Doesn't look very nice ;)

> But I was thinking if I should block signals instead of queueing them in
> a different sigqueue. So Idea is to block signals just before the task
> enables singlestep and unblock after task disables singlestep.

Agreed, this looks much, much better. In both cases the task is current,
it is safe to change ->blocked.

But please avoid sigprocmask(), we have set_current_blocked().

Oleg.

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