From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-872320-1520612520-2-3077408226570638122 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='198.145.29.99', Host='mail.kernel.org', Country='US', FromHeader='org', MailFrom='org' X-Spam-charsets: plain='us-ascii' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: SRS0=NefA=F7=gmail.com=htejun@kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1520612519; b=dmOYhueFvmnJSp1SwHy2O5Q2NMXM9OcdkCvkMdUxi9QN7bv cUFNM0YuTLQHblLMhVO1OkdkMCRLwx3Wm/QxGrRPQ5GDqWOZK7kmJOznbm8E3GXh k06yOyywPMNr8ItnZ7QmYcumyEGLQ1Q9I7riHP0qzJh4m/hveSTnHik49Q+F142L L1G0BXpEt7kkXDiQPaDPjD7QVDjz7y012aAMvoSfbJAyCp+AOGy07ezuwvges8GX HV6nIxfwsb1XU47KndGJqFfHsKxOZcMwDaSXGhpTqJmZmRvOj14FKzhb8kU2nLY6 XgH9nRK52GhazHQbF8bqF8uU+ypC64qmT/j18rA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=sender:date:from:to:cc:subject:message-id :references:mime-version:content-type:in-reply-to; s=arctest; t= 1520612519; bh=9tVU5LF2w9A9q8uDUo++Cqgj94x8Mq979i0Nyj2/8XU=; b=m YMhvrd3Ev0NNYDz44zQmUmbA8HaidxHIXxmWsXsV69LmtQ1ySpjg3Ta6uCGJqWJE RVXSxtNVBSqV93OVEqPW5Atz4seTwcZM9IALUFdkczX1/3C7BWJB/fniMplkdZo2 AJEXicnZnrB46o/ArnOLib3dFgJZMytI0hMQfnkAPq+1ES05q/zGbT4+T/hp7EFO DPAhfa4Vyt78z22sm3y4m9oAqSnujM8JMHeKX/iIhD9E+5Eg1c181RCaXNnbPCXK zC36FGpkJrDnEInM2Rfj/4SkSv5fqm5JX5TteOi+sZTVhAhGUSLyzJowDA2e1xMM bK52JMTTCqPUlZVSK5VrQ== ARC-Authentication-Results: i=1; mx3.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=IDoamUxL x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,d=none) header.from=kernel.org; iprev=pass policy.iprev=198.145.29.99 (mail.kernel.org); spf=none smtp.mailfrom=SRS0=NefA=F7=gmail.com=htejun@kernel.org smtp.helo=mail.kernel.org; x-aligned-from=domain_pass; x-category=clean score=-100 state=0; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=E+1wQ3rf; x-ptr=pass x-ptr-helo=mail.kernel.org x-ptr-lookup=mail.kernel.org; x-return-mx=pass smtp.domain=kernel.org smtp.result=pass smtp_is_org_domain=yes header.domain=kernel.org header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 Authentication-Results: mx3.messagingengine.com; arc=none (no signatures found); dkim=pass (2048-bit rsa key sha256) header.d=gmail.com header.i=@gmail.com header.b=IDoamUxL x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=20161025; dmarc=none (p=none,d=none) header.from=kernel.org; iprev=pass policy.iprev=198.145.29.99 (mail.kernel.org); spf=none smtp.mailfrom=SRS0=NefA=F7=gmail.com=htejun@kernel.org smtp.helo=mail.kernel.org; x-aligned-from=domain_pass; x-category=clean score=-100 state=0; x-google-dkim=pass (2048-bit rsa key) header.d=1e100.net header.i=@1e100.net header.b=E+1wQ3rf; x-ptr=pass x-ptr-helo=mail.kernel.org x-ptr-lookup=mail.kernel.org; x-return-mx=pass smtp.domain=kernel.org smtp.result=pass smtp_is_org_domain=yes header.domain=kernel.org header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128 X-Remote-Delivered-To: security@kernel.org DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 37E21205F4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=htejun@gmail.com X-Google-Smtp-Source: AG47ELuGsZvAdL9Xw9vDNFyWsyZdglagUr+vKI5k5fVSsmjQd5z6oRtdrz8EyU1O5FNq6BkGtEqTXg== Sender: Tejun Heo Date: Fri, 9 Mar 2018 08:21:37 -0800 From: Tejun Heo To: Lai Jiangshan Cc: "Paul E. McKenney" , torvalds@linux-foundation.org, Jann Horn , bcrl@kvack.org, viro@zeniv.linux.org.uk, Kent Overstreet , security@kernel.org, LKML , kernel-team@fb.com Subject: Re: [PATCH 7/7] RCU, workqueue: Implement rcu_work Message-ID: <20180309162137.GC2943022@devbig577.frc2.facebook.com> References: <20180306172657.3060270-1-tj@kernel.org> <20180306173316.3088458-1-tj@kernel.org> <20180306173316.3088458-7-tj@kernel.org> <20180307145408.GC3918@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Hello, On Thu, Mar 08, 2018 at 08:29:53AM +0800, Lai Jiangshan wrote: > I mentioned a subtle use case that user would think it is supported > since the comment doesn't disallow it. > > It is clear that the user expects > the work must be called at least once after the API returns > the work must be called after an RCU grace period > > But in the case when the user expects the work must be called > at least once again after "queue_rcu_work() + an RCU grace period", > the API is not competent to it if the work is queued. > Although the user can detect it by the return value of > queue_rcu_work(), the user hardly makes his expectation > happen by adding appropriate code. We should definitely document it better but it isn't any different from delayed_work, and I don't see a reason to deviate. Thanks. -- tejun