From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [patch -rt 1/2] KVM: use simple waitqueue for vcpu->wq
Date: Fri, 7 Aug 2015 09:41:31 -0700
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Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Steven Rostedt <rostedt@goodmis.org>,
	Paul Mackerras <paulus@samba.org>,
	Marcelo Tosatti <mtosatti@redhat.com>,
	linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org,
	Luiz Capitulino <lcapitulino@redhat.com>,
	Rik van Riel <riel@redhat.com>,
	Steven Rostedt <srostedt@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>, kvm@vger.kernel.org,
	Paolo Bonzini <pbonzini@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
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On Fri, Aug 07, 2015 at 01:14:15PM +0200, Peter Zijlstra wrote:
> On that, we cannot convert completions to swait. Because swait wake_all
> must not happen from IRQ context, and complete_all() typically is used
> from just that.

If swait queues aren't useable from IRQ context they will be fairly
useless.  What's the problem with making them irq safe?