Messages in this thread Patch in this message | | | Date | Sat, 14 May 2005 02:57:53 -0400 | From | Dave Jones <> | Subject | Re: tickle nmi watchdog whilst doing serial writes. |
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On Fri, May 13, 2005 at 11:43:31PM -0700, Andrew Morton wrote: > 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?
Umm.. Despite it being past my bedtime, I'm pretty sure I'm missing something here...
> + while (!(serial_in(up, UART_MSR) & UART_MSR_CTS) && --tmout) > udelay(1);
I don't see how this is any better than the current code. We're doing 1000000 udelays. Whilst we're doing that, the nmi watchdog goes bonkers. > + if (tmout < 1000000) > + touch_nmi_watchdog();
So by the time we do this, its already triggered.
How about..
--- linux-2.6.11/drivers/serial/8250.c~ 2005-05-14 02:49:02.000000000 -0400 +++ linux-2.6.11/drivers/serial/8250.c 2005-05-14 02:54:30.000000000 -0400 @@ -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> @@ -2099,8 +2100,15 @@ static inline void wait_for_xmitr(struct if (up->port.flags & UPF_CONS_FLOW) { tmout = 1000000; while (--tmout && - ((serial_in(up, UART_MSR) & UART_MSR_CTS) == 0)) + ((serial_in(up, UART_MSR) & UART_MSR_CTS) == 0)) { + int cnt=0; udelay(1); + cnt++; + if (cnt==100) { + touch_nmi_watchdog(); + cnt=0; + } + } } } Signed-off-by: Dave Jones <davej@redhat.com> totally uncompiled & untested. I'm not even sure about that magic '100'. I'll let someone less sleep-deprived than myself choose a better number.
Dave
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