threadgroup_lock() guarantees that the target threadgroup will
remain stable - no new task will be added, no new PF_EXITING
will be set and exec won't happen.
Signed-off-by: Mandeep Singh Baines <msb@xxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: containers@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: cgroups@xxxxxxxxxxxxxxx
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul Menage <paul@xxxxxxxxxxxxxx>
---
kernel/cgroup.c | 12 +-----------
1 files changed, 1 insertions(+), 11 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 4166066..6649529 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2130,7 +2130,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
/* as per above, nr_threads may decrease, but not increase. */
BUG_ON(i >= group_size);
- get_task_struct(tsk);
/*
* saying GFP_ATOMIC has no effect here because we did prealloc
* earlier, but it's good form to communicate our expectations.
@@ -2152,7 +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)
- goto out_put_tasks;
+ goto out_free_group_list;
/*
* step 1: check that we can legitimately attach to the cgroup.
@@ -2233,12 +2232,6 @@ out_cancel_attach:
ss->cancel_attach(ss, cgrp, &tset);
}
}
-out_put_tasks:
- /* clean up the array of referenced threads in the group. */
- for (i = 0; i < group_size; i++) {
- tc = flex_array_get(group, i);
- put_task_struct(tc->task);
- }
out_free_group_list:
flex_array_free(group);
return retval;
@@ -2287,14 +2280,12 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
cgroup_unlock();
return -EACCES;
}
- get_task_struct(tsk);
rcu_read_unlock();
} else {
if (threadgroup)
tsk = current->group_leader;
else
tsk = current;
- get_task_struct(tsk);
}
threadgroup_lock(tsk);
@@ -2306,7 +2297,6 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
threadgroup_unlock(tsk);
- put_task_struct(tsk);
cgroup_unlock();
return ret;
}
--
1.7.3.1
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