Re: Kexec, DMA, and SMP

Corey Minyard
2003-02-14T19:50:48Z

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Werner Almesberger wrote:

|Zwane Mwaikambo wrote:
|
|>I don't think suspending devices is safe at that stage since removing
|>devices and walking lists and freeing memory and disabling devices and...
|>kicks up quite a storm.
|
|
|If you *really* don't want to stop devices, you can use the
|"reserved, non-DMA memory" approach, kexec the kernel that
|records the crash dump, and then do a system-wide reset, or
|such.
|
|But if you don't have that - possibly considerable - amount
|of memory to spare, you don't have much of a choice than to
|stop devices. Of course, crash dumps don't need a neat and
|clean shutdown, so you can avoid all the kfrees, and such.
|
|(So adding a special mode to the power management code may
|be too much overhead. Besides, sometimes, you can just pull
|a reset line, and don't have to do anything even remotely
|related to power management.)

True, I didn't mean the high-level power management code directly. But the
PCI API defines a suspend operation that could take a special mode for this.
Or maybe a new field in the PCI structure (and equivalent for other
things, if
there are any). But the suspend and resume operations should at least give
a good idea where its needed and how to use it.

- -Corey
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