linux-kernel - Re: [PATCH 18/28] powerpc,kgdb: Introduce low level trap catching

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Date:	Wed, 17 Feb 2010 09:56:17 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Jason Wessel <jason.wessel@...driver.com>
Cc:	linux-kernel@...r.kernel.org, kgdb-bugreport@...ts.sourceforge.net,
	mingo@...e.hu, Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH 18/28] powerpc,kgdb: Introduce low level trap catching

On Tue, 2010-02-16 at 13:33 -0600, Jason Wessel wrote:

> I took a peek at xmon, and it suffers from the same problem where you
> can place a breakpoint in any part of rcu_lock, notify_die, or
> atomic_notifier_call_chain and meet with recursive faults.  I also
> checked that xmon appears to correctly return so as to continue if the
> exception was not intended for xmon.
> 
> The reason I had not just moved the code block previously is that I was
> not looking to break anything such as xmon, which is the the only other
> user of this function.
> 
> I'll add your ack, if you agree with the new version of the patch.

Almost, just stick a blank line here:

+               /* Debugger is first in line to stop recursive faults in
+                * rcu_lock, notify_die, or atomic_notifier_call_chain */
+               if (debugger_bpt(regs))
+                       return;
----> 
                /* trap exception */
                if (notify_die(DIE_BPT, "breakpoint", regs, 5, 5, SIGTRAP)
                                == NOTIFY_STOP)
                        return;

Please :-)

Acked-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>

Cheers,
Ben.


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