Hello,
I find there is a possible ABBA deadlock in the MHI driver in Linux 5.10:
In mhi_pm_m0_transition():
262: read_lock_bh(&mhi_cntrl->pm_lock);
281: spin_lock_irq(&mhi_cmd->lock);
In mhi_send_cmd():
1181: spin_lock_bh(&mhi_cmd->lock);
1207: read_lock_bh(&mhi_cntrl->pm_lock);
When mhi_pm_m0_transition() and mhi_send_cmd() are concurrently
executed, the deadlock can occur.
I check the code and find a possible case of such concurrent execution:
#CPU1:
mhi_poll (mhi_event->process_event(...))
mhi_process_ctrl_ev_ring
mhi_pm_m0_transition
#CPU2:
mhi_prepare_for_transfer
mhi_prepare_channel
mhi_send_cmd
Note that mhi_poll() and mhi_prepare_for_transfer() are both exported
by EXPORT_SYMBOL.
Thus, I guess these two functions could be concurrently called by a MHI driver.
I am not quite sure whether this possible deadlock is real and how to
fix it if it is real.
Any feedback would be appreciated, thanks :)
Best wishes,
Jia-Ju Bai