Instead of repeatedly locking and unlocking css_set_rwsem inside cgroup_task_migrate(), update cgroup_attach_task() to grab it outside of the loop and update cgroup_task_migrate() to use put_css_set_locked().
Signed-off-by: Tejun Heo <[email protected]> --- kernel/cgroup.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 63d1a4e..ac78311 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1713,10 +1713,13 @@ int cgroup_taskset_size(struct cgroup_taskset *tset) EXPORT_SYMBOL_GPL(cgroup_taskset_size); -/* +/** * cgroup_task_migrate - move a task from one cgroup to another. + * @old_cgrp; the cgroup @tsk is being migrated from + * @tsk: the task being migrated + * @new_cset: the new css_set @tsk is being attached to * - * Must be called with cgroup_mutex and threadgroup locked. + * Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked. */ static void cgroup_task_migrate(struct cgroup *old_cgrp, struct task_struct *tsk, @@ -1724,6 +1727,9 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp, { struct css_set *old_cset; + lockdep_assert_held(&cgroup_mutex); + lockdep_assert_held(&css_set_rwsem); + /* * We are synchronized through threadgroup_lock() against PF_EXITING * setting such that we can't race against cgroup_exit() changing the @@ -1737,9 +1743,7 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp, task_unlock(tsk); /* Update the css_set linked lists if we're using them */ - down_write(&css_set_rwsem); list_move(&tsk->cg_list, &new_cset->tasks); - up_write(&css_set_rwsem); /* * We just gained a reference on old_cset by taking it from the @@ -1747,7 +1751,7 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp, * we're safe to drop it here; it will be freed under RCU. */ set_bit(CGRP_RELEASABLE, &old_cgrp->flags); - put_css_set(old_cset, false); + put_css_set_locked(old_cset, false); } /** @@ -1870,10 +1874,12 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk, * proceed to move all tasks to the new cgroup. There are no * failure cases after here, so this is the commit point. */ + down_write(&css_set_rwsem); for (i = 0; i < group_size; i++) { tc = flex_array_get(group, i); cgroup_task_migrate(tc->cgrp, tc->task, tc->cset); } + up_write(&css_set_rwsem); /* nothing is sensitive to fork() after this point. */ /* -- 1.8.5.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
