From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-3138558-1521737582-2-7788914252993886383 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.25, ME_NOAUTH 0.01, 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='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='uk', MailFrom='org' X-Spam-charsets: plain='us-ascii' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: linux-api-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1521737581; b=UVV7+GSmBpwGOA6aMfE6TeE4REORTvD+oYAbEvRRDVTETsC +eILkSQXeDcuuTsh/4V5yZ40NOsa21lWAifKZHwoaaiXn7znCp3+luFEG6R6EPI7 dQ1DVPJ+Ajbore22QIprbvdimPgFcDVkBMMFXtcwFyY5S35Sc0spcWnwlPMxlx/D oxVQYA9oNW6sKbHXHKSDpNr91WggF/ipfCbuDh0NFGmYadG2fo+EivMJ3v8p6X1K eOvn1hHTy0qG9iLwxfS5lxzzDW0bJVVO0Hcjb8HWxn1l8wUbBHXFWonxMtkYvvwF lnHD+l7X+nL/3FvzV5urpInGhhUQAEWu7N9hsMA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=date:from:to:cc:subject:message-id :references:mime-version:content-type:in-reply-to:sender :list-id; s=arctest; t=1521737581; bh=H/zGSU3mrRlSl4ucRGvzT1ukao z9KBWwNbneb81sEyo=; b=whruqB11Btr0dPkbPiRK+x1X9Z4cMWZ5tz9Erwi5sS OgTz9PXDW0CjgbASD+CbPZ+h6kqj04CjuDZq6/c2qiC8zMXF3FdIXadOKSnItNPX sAvew06HUfoLjZ5aP3jC2wKUo0VPZ+7w9boOfpN8nV+hvpku494yQnvWXVW1WHut B5ucbb3QOmnzPRIhmFTOe2hHpye6vzhy0FhtwH/syjum/93jMlYpSn456ETzRbp4 U3imuqcz4qpyUK/sX4P9qHBp3M4qVDxq3tnPYyUbwLYZBqrASS6aaD/c6HBR2RzJ dTm6vDKvPX5gxl51RHTUBNFMAjkov4bNcPYnf+4lR3nA== ARC-Authentication-Results: i=1; mx5.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=zeniv.linux.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-api-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=zeniv.linux.org.uk header.mx.error=NOERROR header.result=warn header_org.domain=linux.org.uk header_org.result=pass header_is_org_domain=no; x-vs=clean score=-100 state=0 Authentication-Results: mx5.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,has-list-id=yes,d=none) header.from=zeniv.linux.org.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-api-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=zeniv.linux.org.uk header.mx.error=NOERROR header.result=warn header_org.domain=linux.org.uk header_org.result=pass header_is_org_domain=no; x-vs=clean score=-100 state=0 X-ME-VSCategory: clean Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751729AbeCVQw6 (ORCPT ); Thu, 22 Mar 2018 12:52:58 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:35984 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751692AbeCVQw5 (ORCPT ); Thu, 22 Mar 2018 12:52:57 -0400 Date: Thu, 22 Mar 2018 16:52:55 +0000 From: Al Viro To: Christoph Hellwig Cc: Avi Kivity , linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 06/28] aio: implement IOCB_CMD_POLL Message-ID: <20180322165255.GI30522@ZenIV.linux.org.uk> References: <20180321074032.14211-1-hch@lst.de> <20180321074032.14211-7-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180321074032.14211-7-hch@lst.de> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-api-owner@vger.kernel.org X-Mailing-List: linux-api@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Wed, Mar 21, 2018 at 08:40:10AM +0100, Christoph Hellwig wrote: > Simple one-shot poll through the io_submit() interface. To poll for > a file descriptor the application should submit an iocb of type > IOCB_CMD_POLL. It will poll the fd for the events specified in the > the first 32 bits of the aio_buf field of the iocb. > > Unlike poll or epoll without EPOLLONESHOT this interface always works > in one shot mode, that is once the iocb is completed, it will have to be > resubmitted. AFAICS, your wakeup can race with io_cancel(), leading to double fput(). You are checking the "somebody had committed itself to cancelling that thing" bit outside of ->ctx_lock on the wakeup side, and I don't see anything to prevent both getting to __aio_poll_complete() on the same iocb, with obvious results. I might be missing something subtle in there, but then it would be nice to have it covered in commit message...