From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933492AbbENPRs (ORCPT ); Thu, 14 May 2015 11:17:48 -0400 Received: from mail-qg0-f43.google.com ([209.85.192.43]:33416 "EHLO mail-qg0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933403AbbENPRq (ORCPT ); Thu, 14 May 2015 11:17:46 -0400 Date: Thu, 14 May 2015 11:17:42 -0400 From: Tejun Heo To: Sergey Senozhatsky Cc: lizefan@huawei.com, cgroups@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] sched, cgroup: reorganize threadgroup locking Message-ID: <20150514151742.GJ11388@htj.duckdns.org> References: <1431549318-16756-1-git-send-email-tj@kernel.org> <1431549318-16756-2-git-send-email-tj@kernel.org> <20150514010913.GA4441@swordfish> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150514010913.GA4441@swordfish> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Sergey. On Thu, May 14, 2015 at 10:09:13AM +0900, Sergey Senozhatsky wrote: > > +static inline void threadgroup_change_begin(struct task_struct *tsk) > > { > > - down_write(&tsk->signal->group_rwsem); > > + might_sleep(); > > I think cgroup_threadgroup_change_begin()->down_read() already does > might_sleep() check. Sure but it's a layering thing. threadgroup_change_begin() should be called from a blockable context whether the hook users actually make use of it or not. e.g. We want might_sleep() even when !CONFIG_CGROUP. Thanks. -- tejun From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 1/3] sched, cgroup: reorganize threadgroup locking Date: Thu, 14 May 2015 11:17:42 -0400 Message-ID: <20150514151742.GJ11388@htj.duckdns.org> References: <1431549318-16756-1-git-send-email-tj@kernel.org> <1431549318-16756-2-git-send-email-tj@kernel.org> <20150514010913.GA4441@swordfish> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; bh=XyQ4j4pKrSQEgn3Urw1HEWUXeoioZUFkmssxJAUa3Aw=; b=m4YsbeyB+Qg0mbkYsPW+OSGtfZTcHZVfGHCL87FDjn9mnlprHCuhG88ltJE25FHtyg vs9CKYmwaAexp/vFPanr5a2F8JTKQKZlxaSXwQ7lF/lvp/fYrhI610lPiBRNsJ9jdQtQ MCM0Xj2LaOfC2wVyNXHq1KEsrTAHQldz1rY/codg65XHYsFny9740ggMwF8F5mfYVs2T MQwICqbWF3NhkZ/SWoMlsKHcNaFm5UbWgxMaE66+K3XjXL0JWE2RLki9/GReaIf0/idT lqUCa904LapUe/wSdshwM7wag5DTKGN5zPRPNE9Xlafj5zcBmzJXCfef4Yb441vYmJAL 6RJA== Content-Disposition: inline In-Reply-To: <20150514010913.GA4441@swordfish> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Sergey Senozhatsky Cc: lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Hello, Sergey. On Thu, May 14, 2015 at 10:09:13AM +0900, Sergey Senozhatsky wrote: > > +static inline void threadgroup_change_begin(struct task_struct *tsk) > > { > > - down_write(&tsk->signal->group_rwsem); > > + might_sleep(); > > I think cgroup_threadgroup_change_begin()->down_read() already does > might_sleep() check. Sure but it's a layering thing. threadgroup_change_begin() should be called from a blockable context whether the hook users actually make use of it or not. e.g. We want might_sleep() even when !CONFIG_CGROUP. Thanks. -- tejun