From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sander Eikelenboom Subject: Re: Xen-unstable: Regression (on AMD) host boot stuck on (XEN) testing the IO APIC....................... Date: Tue, 26 Aug 2014 12:29:27 +0200 Message-ID: <8210620878.20140826122927@eikelenboom.it> References: <367097038.20140825191202@eikelenboom.it> <53FB783D.5040302@citrix.com> <1283801136.20140825202522@eikelenboom.it> <53FC54A6020000780002D776@mail.emea.novell.com> <53FC572D020000780002D781@mail.emea.novell.com> <53FC541A.9030505@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1XME0M-0006im-BT for xen-devel@lists.xenproject.org; Tue, 26 Aug 2014 10:29:34 +0000 In-Reply-To: <53FC541A.9030505@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Andrew Cooper Cc: xen-devel , Jan Beulich List-Id: xen-devel@lists.xenproject.org Tuesday, August 26, 2014, 11:32:10 AM, you wrote: > On 26/08/14 08:45, Jan Beulich wrote: >>>>> On 26.08.14 at 09:34, wrote: >>> Considering how early this is, the only theory I have is that >>> rcu_pending() may end up constantly returning true, thus always >>> causing RCU_SOFTIRQ to get raised, not allowing the loop in >>> __do_softirq() to ever exit. If that's the case, we seem to have >>> two options: >>> - pass into __print_IO_APIC() whether it's being called from a key >>> handler >>> - only call process_pending_softirqs() when system_state >= >>> SYS_STATE_smp_boot >>> >>> Personally I'd prefer the former option. >> So here's a patch implementing that (the issue clearly isn't limited >> to AMD). >> >> Jan >> >> x86/IO-APIC: don't process softirqs during early boot >> >> Commit e13b320399 ("x86/irq: process softirqs in irq keyhandlers") >> made this unconditional, but the boot time use of __print_IO_APIC() >> (when "apic_verbosity=debug" was given) can't tolerate that. >> >> Reported-by: Sander Eikelenboom >> Signed-off-by: Jan Beulich > Reviewed-by: Andrew Cooper And Tested-by: Sander Eikelenboom Thanks again ! >> >> --- a/xen/arch/x86/io_apic.c >> +++ b/xen/arch/x86/io_apic.c >> @@ -1092,7 +1092,7 @@ static inline void UNEXPECTED_IO_APIC(vo >> { >> } >> >> -static void /*__init*/ __print_IO_APIC(void) >> +static void /*__init*/ __print_IO_APIC(bool_t boot) >> { >> int apic, i; >> union IO_APIC_reg_00 reg_00; >> @@ -1113,7 +1113,8 @@ static void /*__init*/ __print_IO_APIC(v >> printk(KERN_INFO "testing the IO APIC.......................\n"); >> >> for (apic = 0; apic < nr_ioapics; apic++) { >> - process_pending_softirqs(); >> + if ( !boot ) >> + process_pending_softirqs(); >> >> if (!nr_ioapic_entries[apic]) >> continue; >> @@ -1219,7 +1220,7 @@ static void /*__init*/ __print_IO_APIC(v >> for (i = 0; i < nr_irqs_gsi; i++) { >> struct irq_pin_list *entry = irq_2_pin + i; >> >> - if ( !(i & 0x1f) ) >> + if ( !boot && !(i & 0x1f) ) >> process_pending_softirqs(); >> >> if (entry->pin < 0) >> @@ -1242,12 +1243,12 @@ static void /*__init*/ __print_IO_APIC(v >> static void __init print_IO_APIC(void) >> { >> if (apic_verbosity != APIC_QUIET) >> - __print_IO_APIC(); >> + __print_IO_APIC(1); >> } >> >> static void _print_IO_APIC_keyhandler(unsigned char key) >> { >> - __print_IO_APIC(); >> + __print_IO_APIC(0); >> } >> static struct keyhandler print_IO_APIC_keyhandler = { >> .diagnostic = 1, >> >> >>