On Tue, Mar 07, 2017 at 02:16:49PM +0100, Peter Zijlstra wrote: > So I _think_ find_task_by_vpid() can return an already dead task; and > we'll happily increase task->usage.
Hurm, so find_get_context() already does the PF_EXITING test. And then the put_ctx would've been from find_get_context(), not fput(). So still puzzled.