Hi, This is v4 of a series of patches, authored by Mathieu (thanks for your work and for allowing me to try to move this forward), with the intent of fixing a long standing issue of SCHED_DEADLINE bandwidth accounting. As originally reported by Steve [1], when hotplug and/or (certain) cpuset reconfiguration operations take place, DEADLINE bandwidth accounting information is lost since root domains are destroyed and recreated. Mathieu's approach is based on restoring bandwidth accounting info on the newly created root domains by iterating through the (DEADLINE) tasks belonging to the configured cpuset(s). v3 still had issues (IMHO) because __sched_setscheduler() might race with the aforementioned restore operation (and it actually looks racy with cpuset ops in general), but grabbing cpuset_mutex from potential atomic contexs is a no-go. I reworked v3 solution a bit ending-up with something that seems to be working [2]. The idea is simply to trylock such mutex and return -EBUSY to the user if we raced with cpuset ops. It's gross, but didn't find anything better (and working) yet. :/ I also don't particularly like 05/05, as it introduces lot of DEADLINE- iness into cpuset.c. I decided not to change Mathieu's patch for the moment and see if better approaches are suggested (a per-class thing maybe, even though other classes don't suffer from this problem and it is so still going to be DEADLINE specific). I also left out Mathieu's subsequent patches to focus on this crucial fix. They can easily come later, IMHO. Set also available at https://github.com/jlelli/linux.git fixes/deadline/root-domain-accounting-v4 Thanks, - Juri [1] https://lkml.org/lkml/2016/2/3/966 [2] compare -before (that confirms what Steve saw) with -after https://git.io/vhKfW Mathieu Poirier (5): sched/topology: Add check to backup comment about hotplug lock sched/topology: Adding function partition_sched_domains_locked() sched/core: Streamlining calls to task_rq_unlock() sched/core: Prevent race condition between cpuset and __sched_setscheduler() cpuset: Rebuild root domain deadline accounting information include/linux/cpuset.h | 6 ++++ include/linux/sched.h | 5 +++ include/linux/sched/deadline.h | 8 +++++ include/linux/sched/topology.h | 10 ++++++ kernel/cgroup/cpuset.c | 79 +++++++++++++++++++++++++++++++++++++++++- kernel/sched/core.c | 38 ++++++++++++++------ kernel/sched/deadline.c | 31 +++++++++++++++++ kernel/sched/sched.h | 3 -- kernel/sched/topology.c | 32 ++++++++++++++--- 9 files changed, 193 insertions(+), 19 deletions(-) -- 2.14.3 -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
