[PATCH] [ARM] Do not call flush_cache_user_range with mmap_sem held

[Catalin Marinas]

On Wed, 2010-04-28 at 08:32 +0100, Dima Zavin wrote:
> We can't be holding the mmap_sem while calling flush_cache_user_range
> because the flush can fault. If we fault on a user address, the
> page fault handler will try to take mmap_sem again. Since both places
> acquire the read lock, most of the time it succeeds. However, if another
> thread tries to acquire the write lock on the mmap_sem (e.g. mmap) in
> between the call to flush_cache_user_range and the fault, the down_read
> in do_page_fault will deadlock.
> 
> Also, since we really can't be holding the mmap_sem while calling
> flush_cache_user_range AND vma is actually unused by the flush itself,
> get rid of vma as an argument.
> 
> Signed-off-by: Dima Zavin <dima at android.com>
> Cc: Russell King <rmk+kernel at arm.linux.org.uk>
> Cc: Arve Hjønnevåg <arve at android.com>

FWIW (and since I added the USER() macros to the *_coherent_user_range()
functions - commit 32cfb1b1), my view is that this is a safe patch (of
course, Russell has to agree with this as well):

Acked-by: Catalin Marinas <catalin.marinas at arm.com>

-- 
Catalin