linux-kernel - Re: [patch] x86: kvm: Convert i8254/i8259 locks to raw

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Date:	Tue, 23 Feb 2010 20:18:55 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Thomas Gleixner <tglx@...utronix.de>, Avi Kivity <avi@...hat.com>
CC:	KVM <kvm@...r.kernel.org>, Gleb Natapov <gleb@...hat.com>,
	RT <linux-rt-users@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [patch] x86: kvm: Convert i8254/i8259 locks to raw_spinlocks

Thomas Gleixner wrote:
> The i8254/i8259 locks need to be real spinlocks on preempt-rt. Convert
> them to raw_spinlock. No change for !RT kernels.

Doesn't fly for -rt anymore: pic_irq_update runs under this raw lock and
calls kvm_vcpu_kick which tries to wake_up some thread -> scheduling
while atomic.

This used to work up to 956f97cf. -rt for 2.6.31 is not yet affected,
but 2.6.33 should be broken (haven't checked, using kvm-kmod over 2.6.31
ATM). I can provide a patch that restores the deferred kicking if it's
acceptable for upstream.

Jan

-- 
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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