Re: [PATCH 0/2] nvme-fc: fix schedule in atomic context

[Daniel Wagner]

On Fri, Feb 14, 2025 at 09:02:02AM +0100, Daniel Wagner wrote:
> Shinichiro reported [1] the recent change in the nvme-fc setup path [2]
> introduced a bug. I didn't spot the schedule call in
> nvme_change_ctrl_state.
> 
> It turns out the locking is not necessary if we make the state machine a
> bit more restrictive and only allow entering the LIVE state from
> CONNECTING. If we do this, it's possible to ensure we either enter LIVE
> only if there was no connection loss event. Also the connection loss
> event handler should always trigger the reset handler to avoid a
> read-write race on the state machine state variable.
> 
> I've tried to replicate the original problem once again and wrote a new
> blktest which tries to trigger the race condition. I let it run a for a
> while and nothing broke, but I can't be sure it is really gone. The rest
> of the blktests also passed. Unfortunatly, the test box with FC hardware
> is currently not working, so I can't test this with real hardware.
> 
> [1] https://lore.kernel.org/all/denqwui6sl5erqmz2gvrwueyxakl5txzbbiu3fgebryzrfxunm@iwxuthct377m/
> [2] https://lore.kernel.org/all/20250109-nvme-fc-handle-com-lost-v4-3-fe5cae17b492@xxxxxxxxxx/

ping