Thanks Mark, Sorry for all the questions, I am treading on un-familiar ground here. Can anyone think of a way to adjust how long the serial console holds the interrupt when the kernel sends a message? Anyone know what the purpose of this behavior is?
Using the same port in /etc/inittab with: co:2345:respawn:/sbin/agetty -h -t 60 ttyS0 9600 vt102 is not a problem. When I add the kernel option, making it a console, the problem starts. kernel /vmlinuz-2.4.20-20.9smp ro root=LABEL=/ hdc=ide-scsi console=tty0 console=ttyS0,9600n8 I truly appreciate your help, I really did not want a video card, monitor, or keyboard associated with this machine. (Rack mounted, equipment room environment, trying to keep cost, power consumption and heat down. In addition, connecting a monitor is not practical. BIOS settings and everything are done via serial port.) How are others dealing with this issue? Do certain hardware or kernels behave differently? Or does everyone attach keyboards and monitors? >> The serial console likely is blocking interrupts for too long when it >> engages. Zaptel requires interrupts be serviced 1000 times per >> second, for an interrupt latency of < 1ms max. Generally this is not >> a problem, but some systems in linux (e.g. IDE if DMA is enabled, >> Framebuffer console, etc) block interrupts for exceptionally long >> periods of time, thus causing this sort of problem. > > [Snip...] > > I guess in the case of IDE DMA, using hdparm -u1 would remove the > interrupt blocking. DMA on IDE disks is a nice thing to have... > > Richard Thanks Richard, Interesting snip from man hdparm for others: -u Get/set interrupt-unmask flag for the drive. A setting of 1 permits the driver to unmask other interrupts during processing of a disk interrupt, which greatly improves Linux's responsiveness and eliminates "serial port overrun" errors. Use this feature with caution: some drive/controller combinations do not tolerate the increased I/O latencies possible when this feature is enabled, resulting in massive file system corruption. In particular, CMD-640B and RZ1000 (E)IDE interfaces can be unreliable (due to a hardware flaw) when this option is used with kernel versions earlier than 2.0.13. Disabling the IDE prefetch feature of these interfaces (usually a BIOS/CMOS setting) provides a safe fix for the problem for use with earlier kernels. _______________________________________________ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users
