Sometimes return "Connection timed out" when set auto mode continuously

[harveyquta]

When set auto mode continuously, it will sometimes return "Connection timed out". But when set to manual mode, it won't happen.

set auto mode cmd:
busctl set-property xyz.openbmc_project.State.FanCtrl /xyz/openbmc_project/settings/fanctrl/zone2 xyz.openbmc_project.Control.Mode Manual b false; \
busctl set-property xyz.openbmc_project.State.FanCtrl /xyz/openbmc_project/settings/fanctrl/zone0 xyz.openbmc_project.Control.Mode Manual b false; \
busctl set-property xyz.openbmc_project.State.FanCtrl /xyz/openbmc_project/settings/fanctrl/zone1 xyz.openbmc_project.Control.Mode Manual b false;

return:
Failed to set property Manual on interface xyz.openbmc_project.Control.Mode: Connection timed out

But if adding sleep between each busctl cmd, like below, the error will not happen.
busctl set-property xyz.openbmc_project.State.FanCtrl /xyz/openbmc_project/settings/fanctrl/zone2 xyz.openbmc_project.Control.Mode Manual b false; sleep 0.1; \
busctl set-property xyz.openbmc_project.State.FanCtrl /xyz/openbmc_project/settings/fanctrl/zone0 xyz.openbmc_project.Control.Mode Manual b false; sleep 0.1; \
busctl set-property xyz.openbmc_project.State.FanCtrl /xyz/openbmc_project/settings/fanctrl/zone1 xyz.openbmc_project.Control.Mode Manual b false;

[harveyquta]

if set manual mode continuously, the error also will not happen.

[Krellan]

Very strange. I wonder what would be causing this?

[williamspatrick]

Daemon blocked on sysfs calls to update fan speeds and not able to respond to dbus fast enough?

[harveyquta]

Seems like what @williamspatrick said.
After I mark the dbus_call in dbus/dbuswrite.cpp, "Connection timed out" will not happen.
When set manual to false, _redundantWrite will be set to true, and pid will set property mandatorily one time.

[Krellan]

This is a general problem, not just with the setting of automatic mode.

Sometimes D-Bus calls are just straight up forgotten about. The caller receives the timeout. The swampd program receives nothing at all, so it takes no action.

This problem happens rarely enough that it is tricky to debug. Any thoughts?