[c++] [hwmon] std::ifstream read file with timeout so long

[nguyenchanh2201]

In https://github.com/openbmc/phosphor-hwmon => hwmonio.cpp , I saw we use the std::ifstream to open and read a device sensor.

But, I met an issue with it. In case the sensor was disabled (Ex: the Fan was unplugged), the std::ifstream read will take a long time . The timeout in there is so long. It makes my system have a BIG delay in each checking sensor.

Other observation : In case the sensor device is ready, the time for sensor reading is expected.

Measuring std::ifstream reading:

In case unplugged sensor: 91385 microseconds
In case plugged sensor. : 507 microseconds

The patch to measure the std::ifstream reading, please see attachment !

Unexpected behavior you saw

The timeout in there is so long

Expected behavior

Do we have any better solution in this case? take less more timeout.

[spinler]

People have hit this in the past, and they've fixed it in their device driver.

[nguyenchanh2201]

Thank @spinler , please help me give more info the fixing at device driver! Commit , Merg request or any link that you think it's useful with me.

[spinler]

What driver is it?