From: John Villalovos <jvillalo@redhat.com>
Date: Wed, 6 Oct 2010 16:49:29 -0400
Subject: [misc] x86_64: fix hang at Booting processor 1/8 APIC
Message-id: <20101006164928.GA2931@linuxjohn.usersys.redhat.com>
Patchwork-id: 28629
O-Subject: [RHEL5.6 PATCH] Fix system hang at Booting processor 1/8 APIC
Bugzilla: 639851
RH-Acked-by: Prarit Bhargava <prarit@redhat.com>
RH-Acked-by: Stefan Assmann <sassmann@redhat.com>
RH-Acked-by: Dean Nelson <dnelson@redhat.com>

[RHEL 5.6] System hang at Booting processor 1/8 APIC:
https://bugzilla.redhat.com/show_bug.cgi?id=639851

We are seeing an issue on some newer systems where they hang during boot with
the message:
Detected 6.235 MHz APIC timer.
timer: PIT interrupt stopped.
SMP alternatives: switching to SMP code
Booting processor 1/8 APIC 0x2
<hang>

The fix for this is to revert "[x86_64] use apic as main timer if non-stop-apic
timer" Which is commit a82862bfbd127999505b36fc48f7b8ec6637bbb5 and first
appeared in kernel 2.6.18-223

This patch reverts that commit.  The reverted commit is NOT in the upstream kernel.

Developer Testing:
Tested locally on a system that was hanging.  After applying this patch the
system booted normally.

Brew Build:
https://brewweb.devel.redhat.com/taskinfo?taskID=2801573

RHTS Test Passes:
https://rhts.redhat.com/cgi-bin/rhts/jobs.cgi?id=176191
https://rhts.redhat.com/cgi-bin/rhts/jobs.cgi?id=176192
https://rhts.redhat.com/cgi-bin/rhts/jobs.cgi?id=176193
https://rhts.redhat.com/cgi-bin/rhts/jobs.cgi?id=176194

I don't believe the RHTS test passes are related to this patch.

Signed-off-by: Jarod Wilson <jarod@redhat.com>

diff --git a/arch/x86_64/kernel/apic.c b/arch/x86_64/kernel/apic.c
index 9a0b86a..7f08ec4 100644
--- a/arch/x86_64/kernel/apic.c
+++ b/arch/x86_64/kernel/apic.c
@@ -756,7 +756,7 @@ static void setup_APIC_timer(unsigned int clocks)
 	/* Turn off PIT interrupt if we use APIC timer as main timer.
 	   Only works with the PM timer right now
 	   TBD fix it for HPET too. */
-	if ((vxtime.mode == VXTIME_PMTMR || boot_cpu_has(X86_FEATURE_ARAT)) &&
+	if (vxtime.mode == VXTIME_PMTMR &&
 		smp_processor_id() == boot_cpu_id &&
 		apic_runs_main_timer == 1 &&
 		!cpu_isset(boot_cpu_id, timer_interrupt_broadcast_ipi_mask)) {
diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index 11dce35..830c7d6 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -1429,13 +1429,6 @@ void __init time_init(void)
 		tick_nsec = SH_DIV(NSEC_PER_SEC, acthz, 8) / tick_divider;
 	}
 
-	if ((apic_runs_main_timer == 0) && (nohpet == 0) &&
-	    boot_cpu_has(X86_FEATURE_ARAT)) {
-		/* apic timer as main timer */
-		nohpet = 1;
-		apic_runs_main_timer = 1;
-	}
-
 	if (nohpet)
 		vxtime.hpet_address = 0;