Commit 435a7ef5 authored by Dima Zavin's avatar Dima Zavin Committed by Russell King

ARM: 7409/1: Do not call flush_cache_user_range with mmap_sem held

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.

[will: removed drop of vma parameter as already queued by rmk (7365/1)]
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarDima Zavin <dima@android.com>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 3e0f5a15
......@@ -496,7 +496,9 @@ do_cache_op(unsigned long start, unsigned long end, int flags)
if (end > vma->vm_end)
end = vma->vm_end;
up_read(&mm->mmap_sem);
flush_cache_user_range(start, end);
return;
}
up_read(&mm->mmap_sem);
}
......
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