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SubjectRe: QUESTION: Network hangs with BP6 and 2.4.x kernels, hardware


On Sat, 13 Jan 2001, Frank de Lange wrote:

> On Fri, Jan 12, 2001 at 04:36:33PM -0800, Linus Torvalds wrote:
> > It may well not be disable_irq() that is buggy. In fact, there's good
> > reason to believe that it's a hardware problem.
>
> I am inclined to believe it IS a hardware problem... If disable_irq were buggy,
> wouldn't the problem occur more frequently in other irq-heavy areas? A quick
> count shows that disable_irq* is used in 84 sourcefiles in the driver/*
> directory. This includes drivers which generate many interrupts in a short
> timeframe (like ide).

IDE is not my favourite example of a "known stable driver". Also, in many
cases IDE is for historical reasons connected to an EDGE io-apic pin (ie
it's still considered an ISA interrupt). Which probably wouldn't show this
problem anyway.

Also, IDE doesn't generate all that many interrupts. You can make a
network driver do a _lot_ more interrupts than just about any disk driver
by simply sending/receiving a lot of packets. With disks it is very hard
to get the same kind of irq load - Linux will merge the requests and do at
least 1kB worth of transfer per interrupt etc. On a ne2k 100Mbps PCI card,
you can probably _easily_ generate a much higher stream of interrupts.

Linus

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