Hi, On Tue, Apr 02, 2024 at 07:42:03PM +0200, Greg KH wrote: > 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@xxxxxxxxxxx> > > > > > 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: > > > > > 1. CFS task (affined to a particular CPU) takes rwsem lock. > > > > > > > > > > 2. CFS task gets preempted by a RT task before setting owner. > > > > > > > > > > 3. 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? It's with a normal "clean" kernel. A.
