Messages in this thread | | | Date | Mon, 11 Oct 1999 01:28:36 +0200 (CEST) | From | Andrea Arcangeli <> | Subject | Re: locking question: do_mmap(), do_munmap() |
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On Sun, 10 Oct 1999, Alexander Viro wrote:
>mm - no list modifications, no vma removal, etc. We could introduce a new >semaphore (spinlocks are not going to work - ->swapout gets vma as
We could add a reference count to each vma protected by a per-mm spinlock. Then we could drop the spinlock in swap_out_mm as soon as we incremented the refcount of the vma. I am talking by memory, I am not sure if it can be really done and if it's the right thing to do this time. (I'll check the code ASAP).
>argument and it can sleep. The question being: where can we trigger >__get_free_pages() with __GFP_WAIT if the mmap_sem is held? And another
All userspace allocations do exactly that.
>one - where do we modify ->mmap? If they can be easily separated -
We modify mmap in the mmap.c and infact we hold the semaphore there too.
The reason they are not separated is that during all the page fault path you can't have _your_ vmas to change under you if another thread is running munmap in parallel.
>eat the fs on the testbox ;-), but I'ld be really grateful if some of VM >people would check the results.
I can check them of course ;).
Andrea
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