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From: "Liu, Chuansheng" <chuansheng.liu@intel.com>
To: "'linux-kernel@vger.kernel.org' (linux-kernel@vger.kernel.org)" 
	<linux-kernel@vger.kernel.org>
CC: "tglx@linutronix.de" <tglx@linutronix.de>, "hpa@zytor.com" <hpa@zytor.com>
Subject: [PATCH] x86_dump_trace: avoiding endless " <IRQ> " is printed
Thread-Topic: [PATCH] x86_dump_trace: avoiding endless " <IRQ> " is printed
Thread-Index: Ac15MsI6ncx2OLFBSBevzwjQUyIXXg==
Date: Mon, 13 Aug 2012 09:05:23 +0000
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From: liu chuansheng <chuansheng.liu@intel.com>
Subject: [PATCH] x86_dump_trace: avoiding endless " <IRQ> " is printed

Found the case that endless " <IRQ> " printing in dump_trace,
and no real meaningful stack traces are output, so there should
one rare case that possibly context->previous_esp = context or
other cases.

The endless " <IRQ> " is as below:
...
[   82.215244,0]  <IRQ>
[   82.215399,0]  <IRQ>
[   82.215554,0]  <IRQ>
[   82.215710,0]  <IRQ>
[   82.215865,0]  <IRQ>
[   82.216022,0]  <IRQ>
[   82.216178,0]  <IRQ>
[   82.216333,0]  <IRQ>
[   82.216488,0]  <IRQ>
[   82.216643,0]  <IRQ>
[   82.216798,0]  <IRQ>
[   82.216953,0]  <IRQ>
...

This patch aim is:
1/ Limiting the " <IRQ> " outputing, currently the max IRQ contexts
is 2(softirq+harirq combination);
2/ When the max IRQ contexts 2 is reached, print the context content
to confirm;

Signed-off-by: liu chuansheng <chuansheng.liu@intel.com>
---
 arch/x86/kernel/dumpstack_32.c |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index 1038a41..5387429 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -22,6 +22,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
                const struct stacktrace_ops *ops, void *data)
 {
        int graph = 0;
+       int dump_irq = 0;
 
        if (!task)
                task = current;
@@ -47,8 +48,18 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
                stack = (unsigned long *)context->previous_esp;
                if (!stack)
                        break;
+
+               if (unlikely(dump_irq > 2)) {
+                       printk(KERN_WARNING "break multi-IRQ print,"
+                               "context=%08lx, stack=%08lx\n",
+                               (unsigned long)context,
+                               (unsigned long)stack);
+                       break;
+               }
+
                if (ops->stack(data, "IRQ") < 0)
                        break;
+               dump_irq++;
                touch_nmi_watchdog();
        }
 }
-- 
1.7.0.4
--
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