6d206b1ea9
The cooling levels array is supposed to prevent the system fans from
being configured below a 20% duty cycle as otherwise some of them get
stuck at 0 RPM.
Due to an off-by-one error, the last element in the array was not
initialized, causing it to be set to zero, which in turn lead to fans
being configured with a 0% duty cycle in maximum cooling state.
Since commit 332fdf951df8 ("mlxsw: thermal: Fix out-of-bounds memory
accesses") the contents of the array are static. Therefore, instead of
fixing the initialization of the array, simply remove it and adjust
thermal_cooling_device_ops::set_cur_state() so that the configured duty
cycle is never set below 20%.
Before:
# cat /sys/class/thermal/thermal_zone0/cdev0/type
mlxsw_fan
# echo 10 > /sys/class/thermal/thermal_zone0/cdev0/cur_state
# cat /sys/class/hwmon/hwmon0/name
mlxsw
# cat /sys/class/hwmon/hwmon0/pwm1
0
After:
# cat /sys/class/thermal/thermal_zone0/cdev0/type
mlxsw_fan
# echo 10 > /sys/class/thermal/thermal_zone0/cdev0/cur_state
# cat /sys/class/hwmon/hwmon0/name
mlxsw
# cat /sys/class/hwmon/hwmon0/pwm1
255
This bug was uncovered when the thermal subsystem repeatedly tried to
configure the cooling devices to their maximum state due to another
issue [1]. This resulted in the fans being stuck at 0 RPM, which
eventually lead to the system undergoing thermal shutdown.
[1] https://lore.kernel.org/netdev/ZA3CFNhU4AbtsP4G@shredder/
Fixes: a421ce088ac8 ("mlxsw: core: Extend cooling device with cooling levels")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Vadim Pasternak <vadimp@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.