On Tue, Nov 3, 2020 at 11:33 AM Robert Hancock
<robert.hancock@xxxxxxxxxx> wrote:
>
> As part of commit a919ba06979a7 ("hwmon: (pmbus) Stop caching register
> values"), the update of the sensor value is now triggered directly by the
> sensor attribute value being read from sysfs. This created (or at least
> made much more likely) a locking issue, since nothing protected the device
> page selection from being unexpectedly modified by concurrent reads. If
> sensor values on different pages on the same device were being concurrently
> read by multiple threads, this could cause spurious read errors due to the
> page register not reading back the same value last written, or sensor
> values being read from the incorrect page.
>
> Add locking of the update_lock mutex in pmbus_show_sensor and
> pmbus_show_samples so that these cannot result in concurrent reads from the
> underlying device.
>
> Fixes: a919ba06979a7 ("hwmon: (pmbus) Stop caching register values")
> Signed-off-by: Robert Hancock <robert.hancock@xxxxxxxxxx>
Reviewed-by: Alex Qiu <xqiu@xxxxxxxxxx>
Hi Robert,
Thanks for raising this issue up!
- Alex Qiu
