Re: locking question: do_mmap(), do_munmap()

Stephen C. Tweedie (sct@redhat.com)
Mon, 11 Oct 1999 23:22:42 +0100 (BST)


Hi,

On Mon, 11 Oct 1999 20:02:40 +0200, Manfred Spraul
<manfreds@colorfullife.com> said:

> What about something like a rw-semaphore which protects the vma list:
> vma-list modifiers [ie merge_segments(), insert_vm_struct() and
> do_munmap()] grab it exclusive, swapper grabs it "shared, starve
> exclusive".

Deadlock. Process A tries to do an mmap on mm A, gets the exclusive
lock, tries to swap out from process B, and grabs mm B's shared lock.
Process B in the mean time is doing the same thing and has an exclusive
lock on mm B, and is trying to share-lock A. Whoops.

> This should not dead-lock,

Are you sure?!

--Stephen

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/