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

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Date:	Mon, 27 Aug 2012 23:47:11 +0000
From:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
To:	"Gross, Mark" <mark.gross@...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.
Feels dumpstack_64.c has different with dumpstack_32 which just has three types stacks for normal thread, hardirq and softirq,
so just want to use this patch to cover x86_32 case and it is the real case I meet also, thanks.

> -----Original Message-----
> From: Gross, Mark
> Sent: Monday, August 27, 2012 11:50 PM
> To: Liu, Chuansheng; 'linux-kernel@...r.kernel.org'
> (linux-kernel@...r.kernel.org)
> Cc: hpa@...ux.intel.com; alan@...ux.intel.com; Pan, Jacob jun
> 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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