Author :
dtucker
Date :
2020-07-15 11:33:12
Hash :24c7ba2a Message :Run the sxitemp(4) at IPL_SOFTCLOCK instead of IPL_VM. Prevents "panic:
mtx ...: locking against myself" on Orange Pi Zero.
Analysis by patrick@:
"The thermal sensor framework uses its own taskq with IPL_SOFTCLOCK.
sxitemp(4) calls thermal_sensor_update() from interrupt context, and
sxitemp(4) is using IPL_VM (memory allocation?!) for its interrupt.
IPL_VM is obviously higher than IPL_SOFTCLOCK, so it ends up being able
to interrupt the taskq. Even though we're in msleep_nsec, I think we
have *not yet* given up the mutex, that we are holding while looking for
more work, only releasing it while sleeping.
Thus, the interrupt runs task_add(), which tries to grab the taskq's
mutex, even though the taskq already holds it!"
ok patrick@ kettenis@
dtucker