On Thu, Aug 03, 2000 at 11:11:36AM -0400, Theodore Ts'o wrote:
> 1) Serial sysrq is reported no to work for 2.4 kernels.
> I haven't heard of any such reports. I'm currently on the road right
I think you have, actually. I was under the impression the last reply you
sent about it was "Here's how I fixed it".
> now, so I can't test this right away. If someone running 2.4.0test5 can
> test this and confirm/deny this claim, I would appreciate it. If it
> doesn't work, full debugging particulars would be appreciate it.
For the benefit of the list, here is what happened here that made serial
SysRq not work:
wait_for_xmitr currently looks like this:
while (--tmout &&
((serial_in(info, UART_LSR) & BOTH_EMPTY) != BOTH_EMPTY));
The BI bit in the UART's LSR register is cleared on read; this means that
whenever a printk goes out over the serial console, we potentially lose a
break condition. As soon as you enable verbose debugging in the serial
driver, this will always hit you - there's a printk in the interrupt
handler before we read LSR.
Another issue is that very often, UART_LSR_BI isn't set in the
read_status_mask which means sysrq breaks will be ignored as well. I think
it doesn't make a lot of sense this way, and it certainly could be
responsible for some of the "serial SysRq doesn't work" reports.
With those two issues fixed, serial SysRq works fine here.
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This archive was generated by hypermail 2b29 : Mon Aug 07 2000 - 21:00:11 EST