Re: Accessing copy_to_user() from interrupt handler?
Mike Jagdis (mike@toaster.roan.co.uk)
Tue, 26 Nov 1996 13:59:20 GMT
In article <57biop$o9a$1@nova.noris.de>, Matthias Urlichs wrote:
>
>In linux.dev.kernel, article <qm4tii8pyj.fsf@chemie.uni-karlsruhe.de>,
> Klaus-Georg Adams <Klaus-Georg.Adams@chemie.uni-karlsruhe.de> writes:
>>
>> This brings us back to the problem of kmalloc()ing ca. 1MB reliably. I
>> prefer allocating the buffer in the ccd_open() rather than in
>> module_init(). And so far there is no way to tell kmalloc() to page
>> out a couple of user pages if memory is running low instead of
>> failing. vmalloc() works, but then you don't want page faults when
>> reading from the CCD.
>>
>It seems that vmalloc needs an option to actually allocate the pages it
>maps (I was assuming it does that already?).
It does. Also kmalloc does page in order to acquire memory I think.
But it doesn't page if you use GFP_ATOMIC and you *must* use GFP_ATOMIC
from an interrupt because an interrupt handler can't block.
Incidentally the SCSI code uses GFP_ATOMIC all over the damn place
- even from things like init_module. There's a job for someone... :-)
Mike
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