Messages in this thread | | | Date | Fri, 15 Oct 1999 11:58:16 +0200 | From | Ralf Baechle <> | Subject | Re: locking question: do_mmap(), do_munmap() |
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On Wed, Oct 13, 1999 at 09:32:54AM +0200, Manfred Spraul wrote:
> Kanoj Sarcar wrote: > > Here's a primitive patch showing the direction I am thinking of. I do not > > have any problem with a spinning lock, but I coded this against 2.2.10, > > where insert_vm_struct could go to sleep, hence I had to use sleeping > > locks to protect the vma chain. > > I found a few places where I don't know how to change them. > > 1) arch/mips/mm/r4xx0.c: > their flush_cache_range() function internally calls find_vma(). > flush_cache_range() is called by proc/mem.c, and it seems that this > function cannot get the mmap semaphore. > Currently, every caller of flush_cache_range() either owns the kernel > lock or the mmap_sem. > OTHO, this function contains a race anyway [src_vma can go away if > handle_mm_fault() sleeps, src_vma is used at the end of the function.]
The sole reason for fiddling with the VMA is that we try to optimize icache flushing for non-VM_EXEC vmas. This optimization is broken as the MIPS hardware doesn't make a difference between read and execute in page permissions, so the icache might be dirty even though the vma has no exec permission. So I'll have to re-implement this whole things anyway. The other problem is an efficience problem. A call like flush_cache_range(some_mm_ptr, 0, TASK_SIZE) would take a minor eternity and for MIPS64 a full eternity ...
Ralf
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