Re: Linux-2.6.12

From: Richard B. Johnson
Date: Mon Jun 20 2005 - 09:24:52 EST

On Mon, 20 Jun 2005, Hugh Dickins wrote:

Gosh, I thought from the Subject that you'd taken over from Linus,
and were announcing your new release ;)

On Mon, 20 Jun 2005, Richard B. Johnson wrote:

Attempts to run a driver that worked up to shows that
it aparently is no longer possible to nest calls to `down`.
In other words, a procedure that has taken a semaphore can't
then take another semaphore.


The error is 'sleeping function called from invalid context....'

------------[ cut here ]------------
kernel BUG at mm/memory.c:1112!

No, the error is "kernel BUG at mm/memory.c:1112!", which occurs while
it's holding page table lock, from which it doesn't recover very well.

It's the BUG_ON(!pte_none(*pte)) in remap_pte_range. Maybe your page
table is corrupt, maybe your driver is trying to remap_pfn_range on
top of something already mapped.


But of course it is. There is some memory that is mapped into the
driver's address space, used for DMA. It was obtained using
ioremap_nocache(). This memory is then mapped into user-space
when the user executes mmap(). This is how we DMA directly to
user-space. Is this no longer allowed?

Dick Johnson
Penguin : Linux version 2.6.12 on an i686 machine (5537.79 BogoMips).
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