Messages in this thread | | | From | Ed Tomlinson <> | Subject | Re: tickle nmi watchdog whilst doing serial writes. | Date | Sat, 14 May 2005 06:53:57 -0400 |
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Hi,
The message from a+s+T on a serial console (x86_64) is: BUG: soft lockup detected on cpu#0 Its not changed by this patch. Probably would be a good idea to correct this?
Ed
On Saturday 14 May 2005 06:31, Ed Tomlinson wrote: > Suspect this can be triggered using alt+sysreq+T on a busy system with a slow > serial console. Might be a easy way to see if this patch fixes the issue? > > Ed Tomlinson > > On Saturday 14 May 2005 03:07, Andrew Morton wrote: > > Dave Jones <davej@redhat.com> wrote: > > > > > > 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. > > > > But the NMI watchdog won't expire after one second - normally it's set to > > fixe seconds. > > > > > 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; > > > + } > > > + } > > > > <obwhitespacewhine> spose so. > > > > --- 25/drivers/serial/8250.c~tickle-nmi-watchdog-whilst-doing-serial-writes 2005-05-14 00:03:09.000000000 -0700 > > +++ 25-akpm/drivers/serial/8250.c 2005-05-14 00:06:53.000000000 -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 +2099,11 @@ 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 % 1000) == 0) > > + touch_nmi_watchdog(); > > + } > > } > > } > > > > _ > > > > - > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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