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Date: Fri, 7 Oct 2011 18:58:28 +0200
From: Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH v5 3.1.0-rc4-tip 26/26]   uprobes: queue signals while
	thread is singlestepping.
Message-ID: <20111007165828.GA32319@redhat.com>
References: <20110920115938.25326.93059.sendpatchset@srdronam.in.ibm.com> <20110920120517.25326.57657.sendpatchset@srdronam.in.ibm.com> <1317128626.15383.61.camel@twins> <20110927131213.GE3685@linux.vnet.ibm.com> <20111005180139.GA5704@redhat.com> <20111006054710.GB17591@linux.vnet.ibm.com>
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To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>, Linux-mm <linux-mm@kvack.org>, Arnaldo Carvalho de Melo <acme@infradead.org>, Linus Torvalds <torvalds@linux-foundation.org>, Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>, Hugh Dickins <hughd@google.com>, Christoph Hellwig <hch@infradead.org>, Andi Kleen <andi@firstfloor.org>, Thomas Gleixner <tglx@linutronix.de>, Jonathan Corbet <corbet@lwn.net>, Andrew Morton <akpm@linux-foundation.org>, Jim Keniston <jkenisto@linux.vnet.ibm.com>, Roland McGrath <roland@hack.frob.com>, Ananth N Mavinakayanahalli <ananth@in.ibm.com>, LKML <linux-kernel@vger.kernel.org>

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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