Re: alloc_area_pte: page already exists

[Bjorn Wesen]

On Thu, 9 Aug 2001, Andrea Arcangeli wrote:
> > I'm trying to track down a problem which seems to be a race condition
> > vmalloc page table delayed PTE copying", or "you must never
> > call free_kiovec in an interrupt context" etc..)
> 
> The latter is certainly the case. The former could be the case, however

Had some nasty bugs in that case before.. 

> if you know you're running any free_kiovec from irqs remove it and try
> again first.

Yes, I found it. The irq which signals end-of-I/O also frees the kiovec,
which is bad. But it seemed that what would happen then would be deadlocks
(due to the spinlocks) and not races - but I'll try to make it free in a
task or something instead (there is no kernel context for the "calling"
process because the driver is asynchronous so the context which did the
alloc_kiovec etc. has exited when the irq comes later) and see if it works
better.

> BTW, you should also avoid all the kiobuf allocation in all the fast
> paths, try to pre-allocate it in a slow path to deliver higher
> performance. (shortly we'll split the bh/blocks array out of the kiobuf

Ok, that's probably not a problem since the allocation is done in a normal
system-call context.

/Bjorn