Re: tickle nmi watchdog whilst doing serial writes.

Andrew Morton
2005-05-14T06:44:22Z

Dave Jones <davej@redhat.com> wrote:
>
> This was fun. I inserted a music CD with some obnoxious copy-protection
> on it into the drive, and lots of SCSI errors went zipping over to
> the serial console. Unfortunatly, the box was also compiling a kernel,
> playing oggs, and doing a number of other things at the same time,
> so this happened..
>
> NMI Watchdog detected LOCKUP on CPU2CPU 2

OK.. But calling touch_nmi_watchdog() at 1MHz seems a bit excessive, and
might perturb the finely-tuned timing in there.

How's about this?

--- 25/drivers/serial/8250.c~tickle-nmi-watchdog-whilst-doing-serial-writes 2005-05-13 23:37:57.000000000 -0700
+++ 25-akpm/drivers/serial/8250.c 2005-05-13 23:41:36.000000000 -0700
@@ -40,6 +40,7 @@
#include <linux/serial_core.h>
#include <linux/serial.h>
#include <linux/serial_8250.h>
+#include <linux/nmi.h>

#include <asm/io.h>
#include <asm/irq.h>
@@ -2098,9 +2099,10 @@ static inline void wait_for_xmitr(struct
/* Wait up to 1s for flow control if necessary */
if (up->port.flags & UPF_CONS_FLOW) {
tmout = 1000000;
- while (--tmout &&
- ((serial_in(up, UART_MSR) & UART_MSR_CTS) == 0))
+ while (!(serial_in(up, UART_MSR) & UART_MSR_CTS) && --tmout)
udelay(1);
+ if (tmout < 1000000)
+ touch_nmi_watchdog();
}
}

_