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authorOleg Nesterov <oleg@redhat.com>2015-11-27 19:57:19 +0100
committerTejun Heo <tj@kernel.org>2015-11-30 09:48:18 -0500
commitc9e75f0492b248aeaa7af8991a6fc9a21506bc96 (patch)
tree65b6a47aabaa91a19d1f0c01a613d73ab3cecee3 /kernel/fork.c
parent53254f900bd9ff1e3cc5628e76126bb403d9d160 (diff)
downloadlinux-sh-c9e75f0492b248aeaa7af8991a6fc9a21506bc96.tar.gz
cgroup: pids: fix race between cgroup_post_fork() and cgroup_migrate()
If the new child migrates to another cgroup before cgroup_post_fork() calls subsys->fork(), then both pids_can_attach() and pids_fork() will do the same pids_uncharge(old_pids) + pids_charge(pids) sequence twice. Change copy_process() to call threadgroup_change_begin/threadgroup_change_end unconditionally. percpu_down_read() is cheap and this allows other cleanups, see the next changes. Also, this way we can unify cgroup_threadgroup_rwsem and dup_mmap_sem. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Zefan Li <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c9
1 files changed, 3 insertions, 6 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index f97f2c449f5c..fce002ee3ddf 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1368,8 +1368,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
p->real_start_time = ktime_get_boot_ns();
p->io_context = NULL;
p->audit_context = NULL;
- if (clone_flags & CLONE_THREAD)
- threadgroup_change_begin(current);
+ threadgroup_change_begin(current);
cgroup_fork(p);
#ifdef CONFIG_NUMA
p->mempolicy = mpol_dup(p->mempolicy);
@@ -1610,8 +1609,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
proc_fork_connector(p);
cgroup_post_fork(p, cgrp_ss_priv);
- if (clone_flags & CLONE_THREAD)
- threadgroup_change_end(current);
+ threadgroup_change_end(current);
perf_event_fork(p);
trace_task_newtask(p, clone_flags);
@@ -1652,8 +1650,7 @@ bad_fork_cleanup_policy:
mpol_put(p->mempolicy);
bad_fork_cleanup_threadgroup_lock:
#endif
- if (clone_flags & CLONE_THREAD)
- threadgroup_change_end(current);
+ threadgroup_change_end(current);
delayacct_tsk_free(p);
bad_fork_cleanup_count:
atomic_dec(&p->cred->user->processes);