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Re: hrtimer problem on AT91RM9200

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Hello,

On Fri, Sep 11, 2009 at 05:20:44PM +0200, Uwe Kleine-König wrote:
> Hello Bo,
> 
> In the meantime I got access to an at91rm9200, too.  To help me
> reproducing the problem:
I still cannot reproduce, but I found something anyhow.

The problem is that hrtimer_interrupt_hanging decreases min_delta_ns.
(Initially it's 61036.)

I talked to jstultz on irc and both of us are unsure if asserting that
min_delta_ns isn't decreased in hrtimer_interrupt_hanging is enough or
if there is another problem.

Bo, can you please apply the patch below, pass the kernel parameter
ftrace_dump_on_oops (or alternatively do 

	# echo 1 > /proc/sys/kernel/ftrace_dump_on_oops

), reproduce the problem and send the resulting oops?

Best regards
Uwe

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 51bd089..cd72ca9 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -18,6 +18,7 @@
 #include <linux/personality.h>
 #include <linux/kallsyms.h>
 #include <linux/delay.h>
+#include <linux/kdebug.h>
 #include <linux/hardirq.h>
 #include <linux/init.h>
 #include <linux/uaccess.h>
@@ -223,6 +224,8 @@ static void __die(const char *str, int err, struct thread_info *thread, struct p
 		dump_backtrace(regs, tsk);
 		dump_instr(regs);
 	}
+
+	notify_die(DIE_OOPS, str, regs, err, current->thread.trap_no, SIGSEGV);
 }
 
 DEFINE_RAW_SPINLOCK(die_lock);
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 9e308ab..a0c05f3 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1390,8 +1390,16 @@ void hrtimer_interrupt(struct clock_event_device *dev)
 
 	/* Reprogramming necessary ? */
 	if (expires_next.tv64 != KTIME_MAX) {
-		if (tick_program_event(expires_next, force_clock_reprogram))
+		if (tick_program_event(expires_next, force_clock_reprogram)) {
+			if (nr_retries > 1)
+				trace_printk("tick_program_event failed, "
+						"now=%lld, expires_next=%lld, "
+						"nr_retries=%d\n",
+					(long long)now.tv64,
+					(long long)expires_next.tv64,
+				       	nr_retries);
 			goto retry;
+		}
 	}
 
 	if (raise)

-- 
Pengutronix e.K.                              | Uwe Kleine-König            |
Industrial Linux Solutions                    | http://www.pengutronix.de/  |
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