On Tue, Apr 02, 2024 at 08:30:32PM +0300, Aaro Koskinen wrote:
Stable team,
Please cherry-pick this patch into v5.15 stable:
locking/rwsem: Disable preemption while trying for rwsem lock
commit 48dfb5d2560d36fb16c7d430c229d1604ea7d185
It fixes the following bug present in v5.15:
From: Gokul krishna Krishnakumar quic_gokukris@quicinc.com We observe RT task is hogging CPU when trying to acquire rwsem lock which was acquired by a kworker task but before the rwsem owner was set.
Here is the scenario:
CFS task (affined to a particular CPU) takes rwsem lock.
CFS task gets preempted by a RT task before setting owner.
RT task (FIFO) is trying to acquire the lock, but spinning until
RT throttling happens for the lock as the lock was taken by CFS task.
If the RT throttling is disabled, the RT task will remain looping forever in the kernel. If the system is UP, it will lock up completely.
The issue can be easily reproduced by running RT task and normal task which are affined to the same CPU core.
Does this only affect the -rt patchset, or is this an issue with a "clean" kernel release?
thanks,
greg k-h