From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8F830C32771 for ; Mon, 27 Jan 2020 09:30:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 663142168B for ; Mon, 27 Jan 2020 09:30:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="PimJ8yow" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729616AbgA0JaF (ORCPT ); Mon, 27 Jan 2020 04:30:05 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:55677 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726191AbgA0JaF (ORCPT ); Mon, 27 Jan 2020 04:30:05 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580117404; h=from:from:reply-to:subject:subject: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=nDSg7vKNkgUU6jWUsJmpRRkdzJQUOjJxGGK53N4Ir/o=; b=PimJ8yow41winEJrvjM0uws+1/oPWOKGIkQbU5oPxmv3ImPyBl5yCcjC3Qhzlv3jiXIArq xo6BrKHLVMaJ/kr5Wwfb8LmJpiUu3nrDT5E/qNEET8shRMN+0VqgzXFbykB+dwRhUsBpzZ Sn+KR48fVaOn++ib9MB0Sig+zwX9Jkc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-368-U0vpYBDcMXmf1lpVbUuKfQ-1; Mon, 27 Jan 2020 04:29:59 -0500 X-MC-Unique: U0vpYBDcMXmf1lpVbUuKfQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DE97B8024F1; Mon, 27 Jan 2020 09:29:57 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.70]) by smtp.corp.redhat.com (Postfix) with SMTP id D1CC98704A; Mon, 27 Jan 2020 09:29:52 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 27 Jan 2020 10:29:57 +0100 (CET) Date: Mon, 27 Jan 2020 10:29:52 +0100 From: Oleg Nesterov To: madhuparnabhowmik10@gmail.com Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, ebiederm@xmission.com, christian.brauner@ubuntu.com, paulmck@kernel.org, joel@joelfernandes.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, frextrite@gmail.com, rcu@vger.kernel.org Subject: Re: [PATCH] sched.h: Annotate sighand_struct with __rcu Message-ID: <20200127092951.GA1116@redhat.com> References: <20200124045908.26389-1-madhuparnabhowmik10@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200124045908.26389-1-madhuparnabhowmik10@gmail.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On 01/24, madhuparnabhowmik10@gmail.com wrote: > > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -918,7 +918,7 @@ struct task_struct { > > /* Signal handlers: */ > struct signal_struct *signal; > - struct sighand_struct *sighand; > + struct sighand_struct __rcu *sighand; > sigset_t blocked; > sigset_t real_blocked; > /* Restored if set_restore_sigmask() was used: */ > diff --git a/kernel/signal.c b/kernel/signal.c > index bcd46f547db3..9ad8dea93dbb 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -1383,7 +1383,7 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk, > * must see ->sighand == NULL. > */ > spin_lock_irqsave(&sighand->siglock, *flags); > - if (likely(sighand == tsk->sighand)) > + if (likely(sighand == rcu_access_pointer(tsk->sighand))) > break; > spin_unlock_irqrestore(&sighand->siglock, *flags); > } ACK, perhaps you can also cleanup copy_sighand(). rcu_assign_pointer() makes no sense, we should either move it down or simply use RCU_INIT_POINTER(). Oleg.