From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jan Beulich" Subject: Re: [PATCH] irq: Exclude percpu IRQs from being fixed up Date: Thu, 17 Feb 2011 07:52:46 +0000 Message-ID: <4D5CE1DE0200007800032557@vpn.id2.novell.com> References: <1A42CE6F5F474C41B63392A5F80372B2335E978D@shsmsx501.ccr.corp.intel.com> <4D5BF2FE02000078000322EB@vpn.id2.novell.com> <4D5C68AF.3030807@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <4D5C68AF.3030807@intel.com> Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Fengzhe Zhang Cc: Jeremy Fitzhardinge , xen-devel , Eddie Dong , Xin Li List-Id: xen-devel@lists.xenproject.org >>> On 17.02.11 at 01:15, Fengzhe Zhang wrote: > On 2011/2/16 22:53, Jan Beulich wrote: >>>>> On 16.02.11 at 15:26, "Zhang, Fengzhe" = wrote: >>> irq: Exclude percpu IRQs from being fixed up >>> >>> Xen spin unlock uses spurious ipi "lock_kicker_irq" to wake up blocked = vCPUs >>> waiting on that lock. This irq should always be disabled. However, = when Dom0 >>> is shuting down, function fixup_irqs is called which unmasks all irqs. >>> Function unmask_irq effectively re-enables lock_kicker_irq and its = irq=20 > handler >>> is invoked which reports bug and crashes Dom0. >>> >>> This patch sets IRQ_PER_CPU flag in irq desc and excludes percpu IRQs = from >>> being fixed up when taking CPUs down. >>> >>> Signed-off-by: Fengzhe Zhang >>> >>> diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c >>> index 977d8b4..f0f9450 100644 >>> --- a/arch/x86/kernel/irq_64.c >>> +++ b/arch/x86/kernel/irq_64.c >>> @@ -80,6 +80,9 @@ void fixup_irqs(void) >>> if (irq =3D=3D 2) >>> continue; >>> >>> + if (desc->status& IRQ_PER_CPU) >>> + continue; >>> + >>> /* interrupt's are disabled at this point */ >>> spin_lock(&desc->lock); >>> >>> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c >>> index f34e231..26bc55a 100644 >>> --- a/kernel/irq/manage.c >>> +++ b/kernel/irq/manage.c >>> @@ -727,10 +727,9 @@ __setup_irq(unsigned int irq, struct irq_desc = *desc, >>> struct irqaction *new) >>> goto out_thread; >>> } else >>> compat_irq_chip_set_default_handler(desc); >>> -#if defined(CONFIG_IRQ_PER_CPU) >> >> Why? XEN should select IRQ_PER_CPU instead in its Kconfig. >> >> Jan >> > IRQ_PER_CPU switch is not found in current Kconfig. I'm not sure if = this=20 kernel/irq/Kconfig (introduced as a generic option in 2.6.38-rc2). In prior kernel you'd have to add a respective Kconfig item in drivers/xen/Kconfig. > feature is going to be brought back in the short term. I remove the=20 > ifdef to set IRQ_PER_CPU flag in desc by default but still leave the = IRQ=20 > handling logic unchanged. This is a temporary solution to fix system=20 > crash on poweroff. And this is the fix with minimum impact among the=20 > several solutions we tried. But it's more a hack than a fix. And making per-CPU IRQs properly treated as such isn't a bad idea in any case, I would say. Jan