at86rf2xx: Dead lock when sending while receiving

[roberthartung]

The at86rf2xx driver doesn't check the current state when sending. Therefor it is possible, that a deadlock occurs. at86rf2xx_tx_prepare tries to set the state to AT86RF2XX_STATE_TX_ARET_ON, however, if the receiver is currently in BUSY_RX state, the idle_state will be set accordingly.
The send afterwards is still successful, however, the idle_state is wrong. The _isr method of at86rf2xx_netdev.c will set the idle_state afterwards, however it will never be reached and this results in a dead lock.

I will provide a fix shortly: Add busy waiting before sending / switching states.

[roberthartung]

Update: Probably extending at86rf2xx_set_state to also check for BUSY_RX and BUSY_TX might solve the problem. Will update issue accordingly.

[jnohlgard]

Are you working on a PR for this or is this a potential "help wanted" issue?

[roberthartung]

@gebart I am currently trying to figure out what exactly the problem is!

[kaspar030]

Any news here?

[virajsahai]

If this is a "help wanted" candidate..I would like to take this up!

[jnohlgard]

@virajsahai any help is welcome. Feel free to open a PR if you find what the actual problem is.

[DipSwitch]

This is the same bug as described under: #7276 (comment)

It has been tried to be fixed with PR's: #7115 #7275 #7276 #8186

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. If you want me to ignore this issue, please mark it with the "State: don't stale" label. Thank you for your contributions.

[miri64]

@roberthartung Can you check if #12728 fixed this? I think this is the same behavior as described in #11256.