On Wed, Apr 04, 2018 at 06:24:39PM +0300, Kirill Tkhai wrote: > The following situation leads to deadlock: > > [task 1] [task 2] [task 3] > kill_fasync() mm_update_next_owner() copy_process() > spin_lock_irqsave(&fa->fa_lock) read_lock(&tasklist_lock) write_lock_irq(&tasklist_lock) > send_sigio() <IRQ> ... > read_lock(&fown->lock) kill_fasync() ... > read_lock(&tasklist_lock) spin_lock_irqsave(&fa->fa_lock) ... > > Task 1 can't acquire read locked tasklist_lock, since there is > already task 3 expressed its wish to take the lock exclusive. > Task 2 holds the read locked lock, but it can't take the spin lock. > > The patch makes queued_read_lock_slowpath() to give task 1 the same > priority as it was an interrupt handler, and to take the lock That re-introduces starvation scenarios. And the above looks like a proper deadlock that should be sorted by fixing the locking order.