linux-kernel - Re: [GIT PULL] kgdb regression fixes for 2.6.35-rc5

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Date:	Wed, 28 Jul 2010 19:14:42 -0500
From:	Jason Wessel <jason.wessel@...driver.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, kgdb-bugreport@...ts.sourceforge.net
Subject: Re: [GIT PULL] kgdb regression fixes for 2.6.35-rc5

On 07/28/2010 04:26 PM, Linus Torvalds wrote:
> On Wed, Jul 28, 2010 at 2:17 PM, Frederic Weisbecker <fweisbec@...il.com> wrote:
>> I'm sorry I spot it a bit late.
>> There is a little issue in this patch, irqs won't
>> be restored:
>>
>> @@ -588,9 +588,10 @@ int kgdb_ll_trap(int cmd, const char *str,
>>        if (!kgdb_io_module_registered)
>>                return NOTIFY_DONE;
>>
>> +       local_irq_save(flags);
>>        return __kgdb_notify(&args, cmd);
>> +       local_irq_restore(flags);
>>  }
> 
> Yeah, that's obviously crap. I also wonder why __kgdb_notify messes up
> the flags to begin with.
> 

This should not be needed as the irqs should already be off while in the overflow handler.

Sorry for the noise on the one.   I updated the for_linus branch with the final version.


 1 files changed, 7 insertions(+), 2 deletions(-)


--
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -572,7 +572,6 @@ static int __kgdb_notify(struct die_args *args, unsigned long cmd)
 	return NOTIFY_STOP;
 }
 
-#ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
 int kgdb_ll_trap(int cmd, const char *str,
 		 struct pt_regs *regs, long err, int trap, int sig)
 {
@@ -590,7 +589,6 @@ int kgdb_ll_trap(int cmd, const char *str,
 
 	return __kgdb_notify(&args, cmd);
 }
-#endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */
 
 static int
 kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
@@ -625,6 +623,12 @@ int kgdb_arch_init(void)
 	return register_die_notifier(&kgdb_notifier);
 }
 
+static void kgdb_hw_overflow_handler(struct perf_event *event, int nmi,
+		struct perf_sample_data *data, struct pt_regs *regs)
+{
+	kgdb_ll_trap(DIE_DEBUG, "debug", regs, 0, 0, SIGTRAP);
+}
+
 void kgdb_arch_late(void)
 {
 	int i, cpu;
@@ -655,6 +659,7 @@ void kgdb_arch_late(void)
 		for_each_online_cpu(cpu) {
 			pevent = per_cpu_ptr(breakinfo[i].pev, cpu);
 			pevent[0]->hw.sample_period = 1;
+			pevent[0]->overflow_handler = kgdb_hw_overflow_handler;
 			if (pevent[0]->destroy != NULL) {
 				pevent[0]->destroy = NULL;
 				release_bp_slot(*pevent);
--
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