[PATCH 3/5] cgroup: only need to check oldcgrp==newgrp once
From: Mandeep Singh Baines <hidden>
Date: 2011-12-20 23:14:53
Also in:
lkml
Subsystem:
the rest · Maintainer:
Linus Torvalds
In cgroup_attach_proc it is now sufficient to only check that oldcgrp==newcgrp once. Now that we are using threadgroup_lock() during the migrations, oldcgrp will not change. Signed-off-by: Mandeep Singh Baines <redacted> Cc: Tejun Heo <redacted> Cc: Li Zefan <redacted> Cc: containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: KAMEZAWA Hiroyuki <redacted> Cc: Frederic Weisbecker <redacted> Cc: Oleg Nesterov <redacted> Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org> Cc: Paul Menage <redacted> --- kernel/cgroup.c | 17 ++++++----------- 1 files changed, 6 insertions(+), 11 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 6649529..4668a3f 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c@@ -2069,7 +2069,7 @@ static int css_set_prefetch(struct cgroup *cgrp, struct css_set *cg, */ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) { - int retval, i, group_size, nr_migrating_tasks; + int retval, i, group_size; struct cgroup_subsys *ss, *failed_ss = NULL; /* guaranteed to be initialized later, but the compiler needs this */ struct css_set *oldcg;
@@ -2120,7 +2120,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) } /* take a reference on each task in the group to go in the array. */ tsk = leader; - i = nr_migrating_tasks = 0; + i = 0; do { struct task_and_cgroup ent;
@@ -2136,11 +2136,12 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) */ ent.task = tsk; ent.cgrp = task_cgroup_from_root(tsk, root); + /* nothing to do if this task is already in the cgroup */ + if (ent.cgrp == cgrp) + continue; retval = flex_array_put(group, i, &ent, GFP_ATOMIC); BUG_ON(retval != 0); i++; - if (ent.cgrp != cgrp) - nr_migrating_tasks++; } while_each_thread(leader, tsk); /* remember the number of threads in the array for later. */ group_size = i;
@@ -2150,7 +2151,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) /* methods shouldn't be called if no task is actually migrating */ retval = 0; - if (!nr_migrating_tasks) + if (!group_size) goto out_free_group_list; /*
@@ -2173,9 +2174,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) INIT_LIST_HEAD(&newcg_list); for (i = 0; i < group_size; i++) { tc = flex_array_get(group, i); - /* nothing to do if this task is already in the cgroup */ - if (tc->cgrp == cgrp) - continue; /* get old css_set pointer */ task_lock(tc->task); oldcg = tc->task->cgroups;
@@ -2193,9 +2191,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) */ for (i = 0; i < group_size; i++) { tc = flex_array_get(group, i); - /* leave current thread as it is if it's already there */ - if (tc->cgrp == cgrp) - continue; retval = cgroup_task_migrate(cgrp, tc->cgrp, tc->task, true); BUG_ON(retval); }
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1.7.3.1