Yes. And clear it before unlocking (and again, testing if it's already
clear - you mustn't unlock twice, so you must only unlock when the bit
was set).
You also (obviously) need to have somethign that guarantees that the lists
themselves are stable over the whole sequence, but I assume you already
have mmap_sem for reading (since you'd need it anyway just to follow the
list).
And if you have it for writing, it can obviously *act* as the global lock,
since it would already guarantee mutual exclusion on that mm->mmap list.
Linus
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