From: Miao Xie Date: Fri, 16 Jan 2009 02:24:10 +0000 (+0800) Subject: cpuset: fix possible deadlock in async_rebuild_sched_domains X-Git-Tag: v2.6.29-rc4~68^2~5 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f90d4118bacef87894621a3e8aba853fa0c89abc;p=pandora-kernel.git cpuset: fix possible deadlock in async_rebuild_sched_domains Lockdep reported some possible circular locking info when we tested cpuset on NUMA/fake NUMA box. ======================================================= [ INFO: possible circular locking dependency detected ] 2.6.29-rc1-00224-ga652504 #111 ------------------------------------------------------- bash/2968 is trying to acquire lock: (events){--..}, at: [] flush_work+0x24/0xd8 but task is already holding lock: (cgroup_mutex){--..}, at: [] cgroup_lock_live_group+0x12/0x29 which lock already depends on the new lock. ...... ------------------------------------------------------- Steps to reproduce: # mkdir /dev/cpuset # mount -t cpuset xxx /dev/cpuset # mkdir /dev/cpuset/0 # echo 0 > /dev/cpuset/0/cpus # echo 0 > /dev/cpuset/0/mems # echo 1 > /dev/cpuset/0/memory_migrate # cat /dev/zero > /dev/null & # echo $! > /dev/cpuset/0/tasks This is because async_rebuild_sched_domains has the following lock sequence: run_workqueue(async_rebuild_sched_domains) -> do_rebuild_sched_domains -> cgroup_lock But, attaching tasks when memory_migrate is set has following: cgroup_lock_live_group(cgroup_tasks_write) -> do_migrate_pages -> flush_work This patch fixes it by using a separate workqueue thread. Signed-off-by: Miao Xie Signed-off-by: Lai Jiangshan Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed