Re: [PATCH v2] fs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling

[Mingyu Wang]

Hi Oleg,

In the scenario you described, the tasklist_lock reader holding
dev->event_lock is in process context. That explains why the
interrupt-reader handling does not rule out the possible deadlock.


> perhaps it is time to add pid->tasks_lock or abuse pid->lock we already
> have (we would need to make it irq-safe) but this doesn't look nice...

A fix also needs to preserve the synchronization required for process
group traversal.

Mingyu