From patchwork Wed Oct 9 06:05:16 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: hev X-Patchwork-Id: 11180509 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id CCB591575 for ; Wed, 9 Oct 2019 06:06:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AD43520B7C for ; Wed, 9 Oct 2019 06:06:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=hev-cc.20150623.gappssmtp.com header.i=@hev-cc.20150623.gappssmtp.com header.b="rip4MRuL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727363AbfJIGGZ (ORCPT ); Wed, 9 Oct 2019 02:06:25 -0400 Received: from mail-oi1-f193.google.com ([209.85.167.193]:46506 "EHLO mail-oi1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727002AbfJIGGX (ORCPT ); Wed, 9 Oct 2019 02:06:23 -0400 Received: by mail-oi1-f193.google.com with SMTP id k25so742064oiw.13 for ; Tue, 08 Oct 2019 23:06:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=hev-cc.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=Y+9GPoOhQkd1vjT/R/kfNbg6XiPOzhDYEx2wXKpxJ7A=; b=rip4MRuLxRKbEYLy1YE4w3O3PPOi7w2wSYKOiqasHNPIh/Ev8/EDOSEviq9tC1lug+ o/pV3taf7p5JEHK1yy79jNzaAqTSg9QKRS9MW7vi6Sg2eScp8OPiJyeeVafKYQh+pbl0 ASC6U6fCo00dER/kiPFcR+p99aMDTw/7whu5tCPOUFxJz33HcgTh58eQ2y/Lenh6IX/N qek4qqAbUyk8B0UApQWXA7AN0/4eQeGPUmPSjrd6bJL4TS4ii8RzPDwBpL0kF/aTpwj6 PwgxqiSoRhBimXrUpLSuKg6G+l+bJXH9BI/0gNmhs6cLPdX8sHGEhS6nKpGeKfVlZMOl t3Ig== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=Y+9GPoOhQkd1vjT/R/kfNbg6XiPOzhDYEx2wXKpxJ7A=; b=FE3VO+tsY8/6fvnouYFqTQL5bKz66Vp6OFi6Vw7brOsgeJKfr051JmZv671cgc7QAx TjA8f2Mw73NbbanuDm6k1a4N2eiOKx0T4gh7D4JfkAaLGpEel2fWKKNI8hKnlsrKdw4q pqjLXm3wwu73DqqArLZCVgtOALK1DyK/lYjAFLLA7zA3yr1zPw2Tw8evswZpXnpsS54f Rw8Ph1TitoWz/kOasrpb7l6ecZX0dODjQkh+JD40kzVGCZ0ydOB6f/V7AQ9LBvazSI7K Zv3ZyAZ6ZRHFk87/HTssQnrQ7bkAb68VyusFqkrb3POmy3tv/mJVse7FnzudI/1xIHYr s9EQ== X-Gm-Message-State: APjAAAVOtBpi0epUk9lbwYXHv0xlnvUzedmIcj6sTdWWPIwNUdEpvMHl 3AOK4ODoDnuCICthr+WRr518EpA5i1HekIZrbYM= X-Google-Smtp-Source: APXvYqzMqRRhxCkaJC5ejgVi3EFrI3LKlZiFtWlEAqcprwyaDmtuspogFJWg189veCgcyPO3oVjuoA== X-Received: by 2002:aca:882:: with SMTP id 124mr1020541oii.54.1570601181711; Tue, 08 Oct 2019 23:06:21 -0700 (PDT) Received: from hev-sbc.hz.ali.com ([47.89.83.40]) by smtp.gmail.com with ESMTPSA id o23sm396444ote.67.2019.10.08.23.06.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Oct 2019 23:06:20 -0700 (PDT) From: hev To: linux-fsdevel@vger.kernel.org Cc: Heiher , Al Viro , Andrew Morton , Davide Libenzi , Davidlohr Bueso , Dominik Brodowski , Eric Wong , Jason Baron , Linus Torvalds , Roman Penyaev , Sridhar Samudrala , linux-kernel@vger.kernel.org Subject: [PATCH RESEND v5] fs/epoll: Remove unnecessary wakeups of nested epoll Date: Wed, 9 Oct 2019 14:05:16 +0800 Message-Id: <20191009060516.3577-1-r@hev.cc> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Heiher Take the case where we have: t0 | (ew) e0 | (et) e1 | (lt) s0 t0: thread 0 e0: epoll fd 0 e1: epoll fd 1 s0: socket fd 0 ew: epoll_wait et: edge-trigger lt: level-trigger We remove unnecessary wakeups to prevent the nested epoll that working in edge- triggered mode to waking up continuously. Test code: #include #include #include int main(int argc, char *argv[]) { int sfd[2]; int efd[2]; struct epoll_event e; if (socketpair(AF_UNIX, SOCK_STREAM, 0, sfd) < 0) goto out; efd[0] = epoll_create(1); if (efd[0] < 0) goto out; efd[1] = epoll_create(1); if (efd[1] < 0) goto out; e.events = EPOLLIN; if (epoll_ctl(efd[1], EPOLL_CTL_ADD, sfd[0], &e) < 0) goto out; e.events = EPOLLIN | EPOLLET; if (epoll_ctl(efd[0], EPOLL_CTL_ADD, efd[1], &e) < 0) goto out; if (write(sfd[1], "w", 1) != 1) goto out; if (epoll_wait(efd[0], &e, 1, 0) != 1) goto out; if (epoll_wait(efd[0], &e, 1, 0) != 0) goto out; close(efd[0]); close(efd[1]); close(sfd[0]); close(sfd[1]); return 0; out: return -1; } More tests: https://github.com/heiher/epoll-wakeup Cc: Al Viro Cc: Andrew Morton Cc: Davide Libenzi Cc: Davidlohr Bueso Cc: Dominik Brodowski Cc: Eric Wong Cc: Jason Baron Cc: Linus Torvalds Cc: Roman Penyaev Cc: Sridhar Samudrala Cc: linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Signed-off-by: hev Reviewed-by: Roman Penyaev --- fs/eventpoll.c | 16 ---------------- 1 file changed, 16 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index c4159bcc05d9..75fccae100b5 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -671,7 +671,6 @@ static __poll_t ep_scan_ready_list(struct eventpoll *ep, void *priv, int depth, bool ep_locked) { __poll_t res; - int pwake = 0; struct epitem *epi, *nepi; LIST_HEAD(txlist); @@ -738,26 +737,11 @@ static __poll_t ep_scan_ready_list(struct eventpoll *ep, */ list_splice(&txlist, &ep->rdllist); __pm_relax(ep->ws); - - if (!list_empty(&ep->rdllist)) { - /* - * Wake up (if active) both the eventpoll wait list and - * the ->poll() wait list (delayed after we release the lock). - */ - if (waitqueue_active(&ep->wq)) - wake_up(&ep->wq); - if (waitqueue_active(&ep->poll_wait)) - pwake++; - } write_unlock_irq(&ep->lock); if (!ep_locked) mutex_unlock(&ep->mtx); - /* We have to call this outside the lock */ - if (pwake) - ep_poll_safewake(&ep->poll_wait); - return res; }