diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2019-01-28 17:00:13 +0100 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2019-01-31 06:55:57 -0800 |
| commit | 51bee5abeab2058ea5813c5615d6197a23dbf041 (patch) | |
| tree | 5747f7ee7faf9589d1cf49ca690e598b222cef92 /include | |
| parent | af0c9af1b3f66052c369d08be3f60fa9a9559e48 (diff) | |
cgroup/pids: turn cgroup_subsys->free() into cgroup_subsys->release() to fix the accounting
The only user of cgroup_subsys->free() callback is pids_cgrp_subsys which
needs pids_free() to uncharge the pid.
However, ->free() is called from __put_task_struct()->cgroup_free() and this
is too late. Even the trivial program which does
for (;;) {
int pid = fork();
assert(pid >= 0);
if (pid)
wait(NULL);
else
exit(0);
}
can run out of limits because release_task()->call_rcu(delayed_put_task_struct)
implies an RCU gp after the task/pid goes away and before the final put().
Test-case:
mkdir -p /tmp/CG
mount -t cgroup2 none /tmp/CG
echo '+pids' > /tmp/CG/cgroup.subtree_control
mkdir /tmp/CG/PID
echo 2 > /tmp/CG/PID/pids.max
perl -e 'while ($p = fork) { wait; } $p // die "fork failed: $!\n"' &
echo $! > /tmp/CG/PID/cgroup.procs
Without this patch the forking process fails soon after migration.
Rename cgroup_subsys->free() to cgroup_subsys->release() and move the callsite
into the new helper, cgroup_release(), called by release_task() which actually
frees the pid(s).
Reported-by: Herton R. Krzesinski <hkrzesin@redhat.com>
Reported-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/cgroup-defs.h | 2 | ||||
| -rw-r--r-- | include/linux/cgroup.h | 2 |
2 files changed, 3 insertions, 1 deletions
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 8fcbae1b8db0..120d1d40704b 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -602,7 +602,7 @@ struct cgroup_subsys { void (*cancel_fork)(struct task_struct *task); void (*fork)(struct task_struct *task); void (*exit)(struct task_struct *task); - void (*free)(struct task_struct *task); + void (*release)(struct task_struct *task); void (*bind)(struct cgroup_subsys_state *root_css); bool early_init:1; diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 9968332cceed..81f58b4a5418 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -121,6 +121,7 @@ extern int cgroup_can_fork(struct task_struct *p); extern void cgroup_cancel_fork(struct task_struct *p); extern void cgroup_post_fork(struct task_struct *p); void cgroup_exit(struct task_struct *p); +void cgroup_release(struct task_struct *p); void cgroup_free(struct task_struct *p); int cgroup_init_early(void); @@ -697,6 +698,7 @@ static inline int cgroup_can_fork(struct task_struct *p) { return 0; } static inline void cgroup_cancel_fork(struct task_struct *p) {} static inline void cgroup_post_fork(struct task_struct *p) {} static inline void cgroup_exit(struct task_struct *p) {} +static inline void cgroup_release(struct task_struct *p) {} static inline void cgroup_free(struct task_struct *p) {} static inline int cgroup_init_early(void) { return 0; } |