Re: RT and kernel debugger ( 2.6.12rc6 + RT > 48-00 )

[Tom Rini <trini@kernel.crashing.org>]

On Tue, Jun 14, 2005 at 09:20:15AM +0200, Ingo Molnar wrote:
> 
> * kus Kusche Klaus <kus@keba.com> wrote:
> 
> > I was one of those who tried to get kgdb working.
> > 
> > Here I described how far I came:
> > http://www.ussg.iu.edu/hypermail/linux/kernel/0505.1/0700.html
> 
> does ethernet debugging work if you disable the netpoll WARN_ON() that 
> triggers?

With the KGDB at http://kgdb.linsyssoft.com/cvs.htm the following is all
that's needed for PREEMPT_RT to work:
--- linux-2.6.10.orig/drivers/net/kgdb_eth.c
+++ linux-2.6.10/drivers/net/kgdb_eth.c
@@ -55,22 +55,49 @@ static int eth_getDebugChar(void)
 {
 	int chr;
 
-	while (atomic_read(&in_count) == 0)
+#ifdef CONFIG_PREEMPT_RT
+	/*
+	 * A bit hairy. Netpoll API users uses mutexes (indirectly) and
+	 * thus must have interrupts enabled:
+	 */
+	local_irq_enable();
+#endif
+
+	while (atomic_read(&in_count) == 0) {
+		WARN_ON_RT(irqs_disabled());
 		netpoll_poll(&np);
+		WARN_ON_RT(irqs_disabled());
+	}
 
 	chr = in_buf[in_tail++];
 	in_tail &= (IN_BUF_SIZE - 1);
 	atomic_dec(&in_count);
+#ifdef CONFIG_PREEMPT_RT
+	local_irq_disable();
+#endif
 	return chr;
 }
 
 static void eth_flushDebugChar(void)
 {
+#ifdef CONFIG_PREEMPT_RT
+	/*
+	 * A bit hairy. Netpoll API users uses mutexes (indirectly) and
+	 * thus must have interrupts enabled:
+	 */
+	local_irq_enable();
+#endif
+
 	if (out_count && np.dev) {
+		WARN_ON_RT(irqs_disabled());
 		netpoll_send_udp(&np, out_buf, out_count);
+		WARN_ON_RT(irqs_disabled());
 		memset(out_buf, 0, sizeof(out_buf));
 		out_count = 0;
 	}
+#ifdef CONFIG_PREEMPT_RT
+	local_irq_disable();
+#endif
 }
 
 static void eth_putDebugChar(int chr)
--- linux-2.6.10.orig/kernel/kgdb.c
+++ linux-2.6.10/kernel/kgdb.c
@@ -85,7 +85,7 @@ struct kgdb_arch *kgdb_ops = &arch_kgdb_
 
 static const char hexchars[] = "0123456789abcdef";
 
-static spinlock_t slavecpulocks[NR_CPUS];
+static raw_spinlock_t slavecpulocks[NR_CPUS];
 static volatile int procindebug[NR_CPUS];
 atomic_t kgdb_setting_breakpoint;
 struct task_struct *kgdb_usethread, *kgdb_contthread;

-- 
Tom Rini
http://gate.crashing.org/~trini/