From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH 2/5] mm, memcg: narrow the scope of percpu_charge_mutex Date: Tue, 3 Aug 2021 09:11:25 +0200 Message-ID: References: <20210729125755.16871-1-linmiaohe@huawei.com> <20210729125755.16871-3-linmiaohe@huawei.com> <4a3c23c4-054c-2896-29c5-8cf9a4deee98@huawei.com> <95629d91-6ae8-b445-e7fc-b51c888cad59@huawei.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1627974687; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=yTB1aRzTEEw2dTSaIA3iMc8Rd5LQIIGML6amfYHIZt4=; b=bwvEpu8IwlMFzHs+yKzQ5BkflANLVPluliOGC2khS0BvVK9MnKiTUjZtExbHtFh63auwUB A2SyUrkYvGA5kzCzUMoQ2b6UCYU84Nn/R6P49iaFug5gcjrDZ5SLblSEEmEXSS6LWs/dko mnKrOFfiafycrcdUJ2jxarlFUwEfmJk= Content-Disposition: inline In-Reply-To: <95629d91-6ae8-b445-e7fc-b51c888cad59-hv44wF8Li93QT0dZR+AlfA@public.gmane.org> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Miaohe Lin Cc: Roman Gushchin , hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, alexs-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, songmuchun-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On Tue 03-08-21 14:29:13, Miaohe Lin wrote: [...] > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 616d1a72ece3..6210b1124929 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2208,11 +2208,11 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) > */ > static void drain_all_stock(struct mem_cgroup *root_memcg) > { > - static DEFINE_MUTEX(percpu_charge_mutex); > int cpu, curcpu; > + static atomic_t drainer = ATOMIC_INIT(0); > > /* If someone's already draining, avoid adding running more workers. */ > - if (!mutex_trylock(&percpu_charge_mutex)) > + if (atomic_cmpxchg(&drainer, 0, 1) != 0) > return; > /* > * Notify other cpus that system-wide "drain" is running > @@ -2244,7 +2244,7 @@ static void drain_all_stock(struct mem_cgroup *root_memcg) > } > } > put_cpu(); > - mutex_unlock(&percpu_charge_mutex); > + atomic_set(&drainer, 0); atomic_set doesn't imply memory barrier IIRC. Is this safe? -- Michal Hocko SUSE Labs