iavf: get rid of the crit lock
In the Linux kernel, the following vulnerability has been resolved:
iavf: get rid of the crit lock
Get rid of the crit lock. That frees us from the error prone logic of try_locks.
Thanks to netdev_lock() by Jakub it is now easy, and in most cases we were protected by it already - replace crit lock by netdev lock when it was not the case.
Lockdep reports that we should cancel the work under crit_lock [splat1], and that was the scheme we have mostly followed since [1] by Slawomir. But when that is done we still got into deadlocks [splat2]. So instead we should look at the bigger problem, namely "weird locking/scheduling" of the iavf. The first step to fix that is to remove the crit lock. I will followup with a -next series that simplifies scheduling/tasks.
Cancel the work without netdev lock (weird unlock+lock scheme), to fix the [splat2] (which would be totally ugly if we would kept the crit lock).
Extend protected part of iavf_watchdog_task() to include scheduling more work.
Note that the removed comment in iavf_reset_task() was misplaced, it belonged to inside of the removed if condition, so it's gone now.
[splat1] - w/o this patch - The deadlock during VF removal: WARNING: possible circular locking dependency detected sh/3825 is trying to acquire lock: ((work_completion)(&(&adapter->watchdog_task)->work)){+.+.}-{0:0}, at: start_flush_work+0x1a1/0x470 but task is already holding lock: (&adapter->crit_lock){+.+.}-{4:4}, at: iavf_remove+0xd1/0x690 [iavf] which lock already depends on the new lock.
[splat2] - when cancelling work under crit lock, w/o this series, see [2] for the band aid attempt WARNING: possible circular locking dependency detected sh/3550 is trying to acquire lock: ((wq_completion)iavf){+.+.}-{0:0}, at: touch_wq_lockdep_map+0x26/0x90 but task is already holding lock: (&dev->lock){+.+.}-{4:4}, at: iavf_remove+0xa6/0x6e0 [iavf] which lock already depends on the new lock.
[1] fc2e6b3b132a ("iavf: Rework mutexes for better synchronisation") [2] https://github.com/pkitszel/linux/commit/52dddbfc2bb60294083f5711a158a