Hi Peter, On Wed, Apr 29, 2015 at 3:33 PM, Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> wrote: > Hi Prasad, > > On 04/29/2015 06:12 PM, Prasad Koya wrote: >> On Wed, Apr 29, 2015 at 2:07 PM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: >>> On Wed, Apr 29, 2015 at 04:48:01PM -0400, Peter Hurley wrote: >>>> On 04/29/2015 08:30 AM, Greg KH wrote: >>>>> On Wed, Apr 29, 2015 at 08:22:39AM -0400, Peter Hurley wrote: >>>>>> On 04/28/2015 02:17 PM, Greg KH wrote: >>>>>>> On Tue, Apr 28, 2015 at 10:44:31AM -0700, Prasad Koya wrote: > >>>> Basically, the boundary conditions for stable behavior can easily >>>> be exceeded in several circumstances; this is one of them. >>>> >>>> So is trying to printk() a 1Kb log line over 9600 baud. That's nearly >>>> a second with interrupts off; good luck with that. >>>> >> >> Here is a printk outputting a little over 100 chars and an echo of 52 >> chars (I tried manually to reproduce on vanilla kernel) and I see >> buffer overrun. This is at 9600 baud. >> >> [Thu Apr 23 18:58:46 2015]Aboot# echo >> abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzwatchdog_timer_fn: >> watchdog_timer_fn watchdog_timer_fn watchdog_timer_fn >> watchdog_timer_fn watchdog_timer_fn >> [Thu Apr 23 18:58:48 2015]ttyS0: 1 input overrun(s) >> >> So we dont need a really large printk for this to happen. For example, >> a 60 byte (very reasonable size) printk would turn off interrupts for >> about 60ms at 9600 baud. During this 60ms, console input of, say, 20 >> bytes could cause a 16 byte FIFO overrun during that time. > > True, though my statement regarding 1Kb printk() wasn't really aimed at > this particular problem, but a more general statement that some things > with the serial console really need to be solved elsewhere. > > Another idea occurred to me though: does your setup allow for > hardware flow control? I ask because it would be relatively easy > to drop RTS during console output (the console= command line string > even allows for this to be enabled per console but it's not currently > hooked up right now). > Hardware flow control is disabled on our setups. If hardware flow control is supported, I see how "console=ttySx,9600n8r" could have helped drop/raise RTS line. > Regards, > Peter Hurley > > > -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
