Re: [RFC][PATCH] cgroup_threadgroup_rwsem - affects scalability and OOM

[Oleg Nesterov <oleg@redhat.com>]

On 08/09, Balbir Singh wrote:
>
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1406,7 +1406,6 @@ 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;
> -	threadgroup_change_begin(current);
>  	cgroup_fork(p);
>  #ifdef CONFIG_NUMA
>  	p->mempolicy = mpol_dup(p->mempolicy);
> @@ -1558,6 +1557,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
>  	INIT_LIST_HEAD(&p->thread_group);
>  	p->task_works = NULL;
>  
> +	threadgroup_change_begin(current);
>  	/*
>  	 * Ensure that the cgroup subsystem policies allow the new process to be
>  	 * forked. It should be noted the the new process's css_set can be changed
> @@ -1658,6 +1658,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
>  bad_fork_cancel_cgroup:
>  	cgroup_cancel_fork(p);
>  bad_fork_free_pid:
> +	threadgroup_change_end(current);
>  	if (pid != &init_struct_pid)
>  		free_pid(pid);
>  bad_fork_cleanup_thread:
> @@ -1690,7 +1691,6 @@ bad_fork_cleanup_policy:
>  	mpol_put(p->mempolicy);
>  bad_fork_cleanup_threadgroup_lock:
>  #endif
> -	threadgroup_change_end(current);
>  	delayacct_tsk_free(p);
>  bad_fork_cleanup_count:
>  	atomic_dec(&p->cred->user->processes);

I can't really review this change... but it looks good to me.

Oleg.

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