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SubjectRe: IDE + SMP Lockup (no OOPS) in 2.2.12, 2.2.10
Theodore Y. Ts'o wrote:
> Date: Fri, 1 Oct 1999 20:19:34 +0100 (BST)
> From: Alan Cox <>
> Because the IDE layer disables the shared IRQ in question for periods of
> time of you dont have hdparm -u set, and for some periods of time anyway.
> Basically its the IDE code being obnoxious. Fixing the IDE locking would
> improve this, but would be a real pain because older IDE controllers you
> want to disable_irq and stuff to avoid nasty performance problems.
> Actually, it's worse than that. On some older IDE controllers not
> turning off interrupts will cause data corruption on the disk. Read the
> hdparm man page about the -u option..... If it were only performance
> problems, given that it screws over the serial driver, we could make the
> argument to change the default. But given that on some trashy hardware
> it causes data loss, it's harder to make that argument.... or I would
> have made it a long time ago. (hdparm -u should be in the serial HOWTO
> and a number of FAQ's, though!)

Ok, sure, of course. I know that. However as 99% of the users won't be
reading enough manuals to do the hdparm -u1, it is still neccesary to
find out why the 128-byte-fifo-uart is losing characters, while the
standard 16-byte-fifo-uart isn't.

Turns out the trigger level on the new UART was set at 112. That's 16
before the end. Reducing the trigger level 32, fixed a lot, but still
I was able to overrun the new uart at 19k2, while I couldn't overflow
the 16550 at 115k2.


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