linux-kernel - RE: [PATCH RESEND] x86_dump_trace: avoiding endless " <IRQ> " is printed

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Date:	Mon, 27 Aug 2012 15:49:55 +0000
From:	"Gross, Mark" <mark.gross@...el.com>
To:	"Liu, Chuansheng" <chuansheng.liu@...el.com>,
	"'linux-kernel@...r.kernel.org' (linux-kernel@...r.kernel.org)" 
	<linux-kernel@...r.kernel.org>
CC:	"hpa@...ux.intel.com" <hpa@...ux.intel.com>,
	"alan@...ux.intel.com" <alan@...ux.intel.com>,
	"Pan, Jacob jun" <jacob.jun.pan@...el.com>
Subject: RE: [PATCH RESEND] x86_dump_trace: avoiding endless " <IRQ> " is
 printed

Do you think we should add the same change to dumpstack_64.c too.

Looks like you addressed Alan's comments already (i.e. use of unlikely not needed, us %p, and use pr_warn instead of printk)

--mark

> -----Original Message-----
> From: Liu, Chuansheng
> Sent: Sunday, August 26, 2012 6:56 PM
> To: 'linux-kernel@...r.kernel.org' (linux-kernel@...r.kernel.org)
> Cc: hpa@...ux.intel.com; Gross, Mark; alan@...ux.intel.com
> Subject: [PATCH RESEND] x86_dump_trace: avoiding endless " <IRQ> " is
> printed
> 
> From: liu chuansheng <chuansheng.liu@...el.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 be 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;
> 
> Change-Id: I6d72aa71c4c5ff8f9e6ae133b3f6bfec8887750d
> Signed-off-by: liu chuansheng <chuansheng.liu@...el.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..410fa38 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_count = 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 (dump_irq_count > 2) {
> +                       pr_warn("break multi-IRQ print,"
> +                               "context=%p, stack=%p\n",
> +                               context,
> +                               stack);
> +                       break;
> +               }
> +
>                 if (ops->stack(data, "IRQ") < 0)
>                         break;
> +               dump_irq_count++;
>                 touch_nmi_watchdog();
>         }
>  }
> --
> 1.7.0.4
--
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