From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: raw_spinlock_t rules Date: Sun, 19 Sep 2010 18:43:24 +0200 Message-ID: <4C963DAC.4040604@redhat.com> References: <4C960B78.4010804@redhat.com> <1284914302.23787.2749.camel@gandalf.stny.rr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Cc: Thomas Gleixner , linux-kernel , KVM list , Marcelo Tosatti , Ingo Molnar To: Steven Rostedt Return-path: In-Reply-To: <1284914302.23787.2749.camel@gandalf.stny.rr.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 09/19/2010 06:38 PM, Steven Rostedt wrote: > On Sun, 2010-09-19 at 15:09 +0200, Avi Kivity wrote: > > Some time ago, the i8259 emulation code in kvm was changed to use > > raw_spinlock_t, as it was called in a preempt_disable() and > > local_irq_disable() context, which doesn't work with preemptible > > spinlocks used with CONFIG_PREEMPT_RT. > > > > In Linux 2.6.37, the spinlock will no longer be taken in these contexts, > > so I'd like to change it to a normal spinlock_t. However, it is still > > taken in a spin_lock_irq() context. > > > > Is it okay to do this change? I figured since spin_lock_irq() is part > > of the spinlock infrastructure it might to the right thing. > > > > In PREEMPT_RT all interrupts (besides the timer) is converted to a > thread. The spin_lock_irq() will not disable interrupts in PREEMPT_RT, > because it is not needed (irqs are threaded and wont cause a deadlock if > they share the same spin_locks). > > Note, spin_locks used by the timer will must be raw_spin_lock(), and > threaded context must disable interrupts for real before using it. > Thanks. So it looks like we can convert that spinlock. -- error compiling committee.c: too many arguments to function