From: Oleg Nesterov <oleg@redhat.com>
To: Richard Weinberger <richard@nod.at>
Cc: hannes@cmpxchg.org, mhocko@suse.cz, bsingharora@gmail.com,
kamezawa.hiroyu@jp.fujitsu.com, akpm@linux-foundation.org,
vdavydov@parallels.com, tj@kernel.org, handai.szj@taobao.com,
rientjes@google.com, rusty@rustcorp.com.au,
kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org,
cgroups@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC][PATCH] oom: Be less verbose if the oom_control event fd has listeners
Date: Thu, 5 Jun 2014 16:18:41 +0200 [thread overview]
Message-ID: <20140605141841.GA23796@redhat.com> (raw)
In-Reply-To: <1401976841-3899-2-git-send-email-richard@nod.at>
On 06/05, Richard Weinberger wrote:
>
> +int mem_cgroup_has_listeners(struct mem_cgroup *memcg)
> +{
> + int ret = 0;
> +
> + if (!memcg)
> + goto out;
> +
> + spin_lock(&memcg_oom_lock);
> + ret = !list_empty(&memcg->oom_notify);
> + spin_unlock(&memcg_oom_lock);
> +
> +out:
> + return ret;
> +}
Do we really need memcg_oom_lock to check list_empty() ? With or without
this lock we can race with list_add/del anyway, and I guess we do not care.
And perhaps the caller should check memcg != NULL. but this is subjective,
I won't argue.
Oleg.
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WARNING: multiple messages have this Message-ID (diff)
From: Oleg Nesterov <oleg@redhat.com>
To: Richard Weinberger <richard@nod.at>
Cc: hannes@cmpxchg.org, mhocko@suse.cz, bsingharora@gmail.com,
kamezawa.hiroyu@jp.fujitsu.com, akpm@linux-foundation.org,
vdavydov@parallels.com, tj@kernel.org, handai.szj@taobao.com,
rientjes@google.com, rusty@rustcorp.com.au,
kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org,
cgroups@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [RFC][PATCH] oom: Be less verbose if the oom_control event fd has listeners
Date: Thu, 5 Jun 2014 16:18:41 +0200 [thread overview]
Message-ID: <20140605141841.GA23796@redhat.com> (raw)
In-Reply-To: <1401976841-3899-2-git-send-email-richard@nod.at>
On 06/05, Richard Weinberger wrote:
>
> +int mem_cgroup_has_listeners(struct mem_cgroup *memcg)
> +{
> + int ret = 0;
> +
> + if (!memcg)
> + goto out;
> +
> + spin_lock(&memcg_oom_lock);
> + ret = !list_empty(&memcg->oom_notify);
> + spin_unlock(&memcg_oom_lock);
> +
> +out:
> + return ret;
> +}
Do we really need memcg_oom_lock to check list_empty() ? With or without
this lock we can race with list_add/del anyway, and I guess we do not care.
And perhaps the caller should check memcg != NULL. but this is subjective,
I won't argue.
Oleg.
next prev parent reply other threads:[~2014-06-05 14:18 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-05 14:00 oom: Be less verbose Richard Weinberger
2014-06-05 14:00 ` Richard Weinberger
2014-06-05 14:00 ` [RFC][PATCH] oom: Be less verbose if the oom_control event fd has listeners Richard Weinberger
2014-06-05 14:00 ` Richard Weinberger
2014-06-05 14:18 ` Oleg Nesterov [this message]
2014-06-05 14:18 ` Oleg Nesterov
[not found] ` <20140605141841.GA23796-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2014-06-05 15:46 ` Richard Weinberger
2014-06-05 15:46 ` Richard Weinberger
2014-06-05 15:46 ` Richard Weinberger
2014-06-05 16:00 ` Oleg Nesterov
2014-06-05 16:00 ` Oleg Nesterov
[not found] ` <20140605160029.GA28812-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2014-06-05 16:10 ` Richard Weinberger
2014-06-05 16:10 ` Richard Weinberger
2014-06-05 16:10 ` Richard Weinberger
2014-06-05 15:00 ` Michal Hocko
2014-06-05 15:00 ` Michal Hocko
2014-06-05 15:55 ` Richard Weinberger
2014-06-05 15:55 ` Richard Weinberger
2014-06-05 16:18 ` Michal Hocko
2014-06-05 16:18 ` Michal Hocko
[not found] ` <20140605161807.GD15939-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2014-06-05 21:58 ` Richard Weinberger
2014-06-05 21:58 ` Richard Weinberger
2014-06-05 21:58 ` Richard Weinberger
2014-06-05 21:01 ` David Rientjes
2014-06-05 21:01 ` David Rientjes
2014-06-06 9:10 ` Michal Hocko
2014-06-06 9:10 ` Michal Hocko
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