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Re: [PATCH] mips: irq: add statckoverflow detection

To: Adam Jiang <>, linux-mips <>
Subject: Re: [PATCH] mips: irq: add statckoverflow detection
From: David Daney <>
Date: Thu, 26 Aug 2010 09:21:44 -0700
In-reply-to: <>
Original-recipient: rfc822;
References: <> <> <>
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20100720 Fedora/3.0.6-1.fc12 Thunderbird/3.0.6
On 08/25/2010 06:12 PM, Adam Jiang wrote:
2010/8/26 David Daney<>:
It looks like this patch only checks when processing an interrupt, which
doesn't seem like it would give much coverage.

Yes, it is. This is only for detection on the situation which may be
caused by nested interruption. No more coverage to any other cases.
Because to do that is much difficult and unpredicted.

Well, since the default is to run interrupt handlers with interrupts disabled, it seems like it is of little use as you will almost never see nested interrupts.

A solution that shows overflow in all situations would be of more use. Something that could use GCC's -stack-check or related machinery might be interesting.

David Daney

I will revise the bad code style Sergei blamed.


Am I missing something?

David Daney

On 08/20/2010 11:31 PM, wrote:

From: Adam Jiang<>

Add stackoverflow detection to mips arch

Signed-off-by: Adam Jiang<>
  arch/mips/Kconfig.debug |    7 +++++++
  arch/mips/kernel/irq.c  |   19 +++++++++++++++++++
  2 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/arch/mips/Kconfig.debug b/arch/mips/Kconfig.debug
index 43dc279..f1a00a2 100644
--- a/arch/mips/Kconfig.debug
+++ b/arch/mips/Kconfig.debug
@@ -67,6 +67,13 @@ config CMDLINE_OVERRIDE

          Normally, you will choose 'N' here.

+       bool "Check for stack overflows"
+       depends on DEBUG_KERNEL
+       help
+         This option will cause messages to be printed if free stack
+         drops below a certain limit.
        bool "Enable stack utilization instrumentation"
        depends on DEBUG_KERNEL
diff --git a/arch/mips/kernel/irq.c b/arch/mips/kernel/irq.c
index c6345f5..6334037 100644
--- a/arch/mips/kernel/irq.c
+++ b/arch/mips/kernel/irq.c
@@ -151,6 +151,22 @@ void __init init_IRQ(void)

+static inline void check_stack_overflow(void)
+       long sp;
+       asm volatile("move %0, $sp" : "=r" (sp));
+       sp = sp&    (THREAD_SIZE-1);
+       /* check for stack overflow: is there less then 2KB free? */
+       if (unlikely(sp<    (sizeof(struct thread_info) + 2048))) {
+               printk("do_IRQ: stack overflow: %ld\n",
+                      sp - sizeof(struct thread_info));
+               dump_stack();
+       }
   * do_IRQ handles all normal device IRQ's (the special
   * SMP cross-CPU interrupts have their own specific
@@ -159,6 +175,9 @@ void __init init_IRQ(void)
  void __irq_entry do_IRQ(unsigned int irq)
+       check_stack_overflow();

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