On Wed, Aug 21, 2019 at 03:25:01PM +0200, Thomas Gleixner wrote: > On Wed, 21 Aug 2019, Frederic Weisbecker wrote: > > > On Mon, Aug 19, 2019 at 04:31:48PM +0200, Thomas Gleixner wrote: > > > run_posix_cpu_timers() is called from the timer interrupt. The posix timer > > > expiry always affects the current task which got interrupted. > > > > > > sighand locking is only racy when done on a foreign task, which must use > > > lock_task_sighand(). But in case of run_posix_cpu_timers() that's > > > pointless. > > > > > > sighand of a task can only be dropped or changed by the task itself. Drop > > > happens in do_exit() > > > > Well, that's only in case of autoreap. Otherwise this is dropped by the > > reaper. > > Right, but in the reaper case the task cannot be on the CPU running and > being interrupted by the tick. I might be missing something subtle though.
That looks possible. After exit_notify() and until the final schedule(), the exiting task can execute concurrently with the reaper calling release_task().