Sasha reports various nasty trinity crashes when shmem_fault() tries
to finish_wait(), we guess from rare cases when the wait_queue_head
on shmem_fallocate()'s stack has already gone.  Fix those by using
TASK_UNINTERRUPIBLE instead of TASK_KILLABLE in prepare_to_wait(),
that's much simpler and safer: TASK_KILLABLE was a nice aspiration,
but not worth any more hassle.

Reported-and-tested-by: Sasha Levin <[email protected]>
Signed-off-by: Hugh Dickins <[email protected]>
---
Andrew, please fold this into
shmem-fix-faulting-into-a-hole-not-taking-i_mutex.patch
before sending the fixes on to Linus - thanks.

 mm/shmem.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- mmotm/mm/shmem.c    2014-07-22 16:35:49.683985586 -0700
+++ linux/mm/shmem.c    2014-07-22 16:36:35.459984108 -0700
@@ -1283,7 +1283,7 @@ static int shmem_fault(struct vm_area_st
 
                        shmem_falloc_waitq = shmem_falloc->waitq;
                        prepare_to_wait(shmem_falloc_waitq, &shmem_fault_wait,
-                                       TASK_KILLABLE);
+                                       TASK_UNINTERRUPTIBLE);
                        spin_unlock(&inode->i_lock);
                        schedule();
--
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