linux-kernel - [PATCH V2] x86/smp: Fix cpuN startup panic

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Date:	Mon, 13 Aug 2012 13:04:37 +0900
From:	"Chen, LinX Z" <linx.z.chen@...el.com>
To:	linux-kernel@...r.kernel.org
CC:	mingo@...hat.com, tglx@...utronix.de, hpa@...or.com,
	yanmin_zhang@...ux.intel.com
Subject: [PATCH V2] x86/smp: Fix cpuN startup panic

From: Lin Chen <linx.z.chen@...el.com>

We hit a panic while doing cpu hotplug test.
<0>[  627.982857] Kernel panic - not syncing: smp_callin: CPU1 started up but did not get a callout!
<0>[  627.982864]
<4>[  627.982876] Pid: 0, comm: kworker/0:1 Tainted: G ...
<4>[  627.982883] Call Trace:
<4>[  627.982903]  [<c18f2977>] panic+0x66/0x16c
<4>[  627.982918]  [<c12234cc>] ? default_get_apic_id+0x1c/0x40
<4>[  627.982931]  [<c18ef96d>] start_secondary+0xda/0x252

During BSP bootup AP, it is possible that BSP be preempted before
finishing STARTUP sequence of AP(set cpu_callout_mask) which maybe cause
AP busy wait for it. At present, AP will wait for 2 seconds then panic.

This patch let AP waits for 60 seconds at maximum.

Signed-off-by: Yanmin Zhang <yanmin_zhang@...ux.intel.com>
Signed-off-by: Chen LinX <linx.z.chen@...el.com>
---
  arch/x86/kernel/smpboot.c |    4 ++--
  1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 7c5a8c3..447aa3b 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -162,9 +162,9 @@ static void __cpuinit smp_callin(void)
  	 */

  	/*
-	 * Waiting 2s total for startup (udelay is not yet working)
+	 * Waiting 60s total for startup (udelay is not yet working)
  	 */
-	timeout = jiffies + 2*HZ;
+	timeout = jiffies + 60*HZ;
  	while (time_before(jiffies, timeout)) {
  		/*
  		 * Has the boot CPU finished it's STARTUP sequence?
-- 
1.7.1
--
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