Re: real time hang w/ latency tracing

Daniel Walker
2007-04-04T01:41:30Z

On Tue, 2007-04-03 at 11:57 -0700, Daniel Walker wrote:
> With 2.6.21-rc5-rt8 / i386 . If I disable wakeup timing , and enable
> interrupt off timing with latency tracing I can cause,
>
> BUG: scheduling with irqs disabled: IRQ-16/0x00000000/909
> caller is rt_spin_lock_slowlock+0x94/0x190
> [<c010577a>] show_trace_log_lvl+0x3a/0x60
> [<c0105fdd>] show_trace+0x2d/0x30
> [<c01060c7>] dump_stack+0x27/0x30
> [<c03f52db>] schedule+0x12b/0x130
> [<c03f6314>] rt_spin_lock_slowlock+0x94/0x190
> [<c03f6b35>] rt_spin_lock+0x25/0x30
> [<c02f19bf>] serial8250_console_write+0x16f/0x190
> [<c012b3aa>] __call_console_drivers+0x7a/0xa0
> [<c012b427>] _call_console_drivers+0x57/0xa0
> [<c012b58d>] release_console_sem+0xdd/0x1e0
> [<c012bd46>] vprintk+0x226/0x3b0
> [<c012bef0>] printk+0x20/0x30
> [<c0158d29>] print_traces+0x49/0x100
> [<c0105792>] show_trace_log_lvl+0x52/0x60
> [<c0105fdd>] show_trace+0x2d/0x30
> [<c01060c7>] dump_stack+0x27/0x30
> [<c0158481>] check_critical_timing+0x2b1/0x380
> [<c01585f6>] trace_hardirqs_on+0xa6/0xc0
> [<c01046e5>] restore_nocheck+0x12/0x15

This allows the system to continue printing ..

Signed-Off-By: Daniel Walker <dwalker@mvista.com>

---
include/linux/serial_core.h | 4 ++++
1 file changed, 4 insertions(+)

Index: linux-2.6.20/include/linux/serial_core.h
===================================================================
--- linux-2.6.20.orig/include/linux/serial_core.h
+++ linux-2.6.20/include/linux/serial_core.h
@@ -213,7 +213,11 @@ struct uart_icount {
typedef unsigned int __bitwise__ upf_t;

struct uart_port {
+#ifdef CONFIG_LATENCY_TIMING
+ raw_spinlock_t lock; /* port lock */
+#else
spinlock_t lock; /* port lock */
+#endif
unsigned int iobase; /* in/out[bwl] */
unsigned char __iomem *membase; /* read/write[bwl] */
unsigned int irq; /* irq number */