From patchwork Tue Dec 22 14:52:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yongji Xie X-Patchwork-Id: 11986855 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=-16.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 950CAC433E6 for ; Tue, 22 Dec 2020 14:54:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6395C229CA for ; Tue, 22 Dec 2020 14:54:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727758AbgLVOyd (ORCPT ); Tue, 22 Dec 2020 09:54:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43466 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727674AbgLVOyZ (ORCPT ); Tue, 22 Dec 2020 09:54:25 -0500 Received: from mail-pf1-x434.google.com (mail-pf1-x434.google.com [IPv6:2607:f8b0:4864:20::434]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EC09CC061257 for ; Tue, 22 Dec 2020 06:53:17 -0800 (PST) Received: by mail-pf1-x434.google.com with SMTP id t22so8615651pfl.3 for ; Tue, 22 Dec 2020 06:53:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=hq6cLGhX+YOdloZCBCv76n2UjaYC8NZfkFs6/p+ZtOg=; b=y40ttjV/YgM4wvX349wPEo/KuCxAMjRA2ZGiQMlh4+FFb89YrcRj657ZyIInGzamOW 0vfsCDqIluk6oIsB2jIj87YdKSM/exKmrbFfY4NkHc0YRPVvxD1OzSOfHVxKTOTiLzAd tDe5wUQyRxNUbx5fMBoA8omQ1MJbSMpIFuetQZnAfhieIp+CYT7UAaOXwKoXffCnem1D 3V0DJz+Bxy3VchfzYjJwwfj5DFYGxerszby07BkOCNCactVeA6L6eyBtoh7l4VcAwVVM ghNSomkizu0oUUr2IPwpiyVTKNdcXxHRdQYbXfIxvKEvTvFlRJik1/kfoVSrotdEaDwp YYmw== 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:in-reply-to :references:mime-version:content-transfer-encoding; bh=hq6cLGhX+YOdloZCBCv76n2UjaYC8NZfkFs6/p+ZtOg=; b=uU9zc5AuZpnuH2bsAx+qObtJOJa1cQA/vqfxdoa6rvS3MebsQkdmawseeWdWOScijM w8/zrXo62LHt/3KjC2Tzxh9+djydLK+U9ggy2MgUAOyxgwkUKrFakTMgbuHothYU5wWp vNteUbuc7I7DgHID9dOP/a6ouuCtDPh0dnNf7xwQbX7Fw0QNpmdnuOba2zUVTmqscMaB gmu5/guWMhq/5RIUzNearM+bxjPHKSnGnHfpOj51GYmQJuculL5TtIRGAws+UoWEyOuy Q8YiXKUbAT7ZlzD8r/fkTahAOYo88vYl7tAtd59ZY63LXQz8IyNxJVcS8ntlz2ch+EV5 qXIQ== X-Gm-Message-State: AOAM533jz+5k2j2BBVSEkcH4eYrW4sJUKMTn3yLbDLfkbw2pT5g++PlX 8pYR7z+BrpVSb1mXOoqzkCzT X-Google-Smtp-Source: ABdhPJwOIJpirmt9ZpOuYali2BMic+XSa8v1hT8Vzzl1Qawx8gam4Ow7LO4po33/t7B2y9SJvYO7HQ== X-Received: by 2002:a63:a516:: with SMTP id n22mr19707227pgf.125.1608648797542; Tue, 22 Dec 2020 06:53:17 -0800 (PST) Received: from localhost ([139.177.225.248]) by smtp.gmail.com with ESMTPSA id h12sm6357200pgk.70.2020.12.22.06.53.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Dec 2020 06:53:17 -0800 (PST) From: Xie Yongji To: mst@redhat.com, jasowang@redhat.com, stefanha@redhat.com, sgarzare@redhat.com, parav@nvidia.com, akpm@linux-foundation.org, rdunlap@infradead.org, willy@infradead.org, viro@zeniv.linux.org.uk, axboe@kernel.dk, bcrl@kvack.org, corbet@lwn.net Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC v2 02/13] eventfd: track eventfd_signal() recursion depth separately in different cases Date: Tue, 22 Dec 2020 22:52:10 +0800 Message-Id: <20201222145221.711-3-xieyongji@bytedance.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201222145221.711-1-xieyongji@bytedance.com> References: <20201222145221.711-1-xieyongji@bytedance.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Now we have a global percpu counter to limit the recursion depth of eventfd_signal(). This can avoid deadlock or stack overflow. But in stack overflow case, it should be OK to increase the recursion depth if needed. So we add a percpu counter in eventfd_ctx to limit the recursion depth for deadlock case. Then it could be fine to increase the global percpu counter later. Signed-off-by: Xie Yongji --- fs/aio.c | 3 ++- fs/eventfd.c | 20 +++++++++++++++++++- include/linux/eventfd.h | 5 +---- 3 files changed, 22 insertions(+), 6 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 1f32da13d39e..5d82903161f5 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1698,7 +1698,8 @@ static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, list_del(&iocb->ki_list); iocb->ki_res.res = mangle_poll(mask); req->done = true; - if (iocb->ki_eventfd && eventfd_signal_count()) { + if (iocb->ki_eventfd && + eventfd_signal_count(iocb->ki_eventfd)) { iocb = NULL; INIT_WORK(&req->work, aio_poll_put_work); schedule_work(&req->work); diff --git a/fs/eventfd.c b/fs/eventfd.c index e265b6dd4f34..2df24f9bada3 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -25,6 +25,8 @@ #include #include +#define EVENTFD_WAKE_DEPTH 0 + DEFINE_PER_CPU(int, eventfd_wake_count); static DEFINE_IDA(eventfd_ida); @@ -42,9 +44,17 @@ struct eventfd_ctx { */ __u64 count; unsigned int flags; + int __percpu *wake_count; int id; }; +bool eventfd_signal_count(struct eventfd_ctx *ctx) +{ + return (this_cpu_read(*ctx->wake_count) || + this_cpu_read(eventfd_wake_count) > EVENTFD_WAKE_DEPTH); +} +EXPORT_SYMBOL_GPL(eventfd_signal_count); + /** * eventfd_signal - Adds @n to the eventfd counter. * @ctx: [in] Pointer to the eventfd context. @@ -71,17 +81,19 @@ __u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n) * it returns true, the eventfd_signal() call should be deferred to a * safe context. */ - if (WARN_ON_ONCE(this_cpu_read(eventfd_wake_count))) + if (WARN_ON_ONCE(eventfd_signal_count(ctx))) return 0; spin_lock_irqsave(&ctx->wqh.lock, flags); this_cpu_inc(eventfd_wake_count); + this_cpu_inc(*ctx->wake_count); if (ULLONG_MAX - ctx->count < n) n = ULLONG_MAX - ctx->count; ctx->count += n; if (waitqueue_active(&ctx->wqh)) wake_up_locked_poll(&ctx->wqh, EPOLLIN); this_cpu_dec(eventfd_wake_count); + this_cpu_dec(*ctx->wake_count); spin_unlock_irqrestore(&ctx->wqh.lock, flags); return n; @@ -92,6 +104,7 @@ static void eventfd_free_ctx(struct eventfd_ctx *ctx) { if (ctx->id >= 0) ida_simple_remove(&eventfd_ida, ctx->id); + free_percpu(ctx->wake_count); kfree(ctx); } @@ -423,6 +436,11 @@ static int do_eventfd(unsigned int count, int flags) kref_init(&ctx->kref); init_waitqueue_head(&ctx->wqh); + ctx->wake_count = alloc_percpu(int); + if (!ctx->wake_count) { + kfree(ctx); + return -ENOMEM; + } ctx->count = count; ctx->flags = flags; ctx->id = ida_simple_get(&eventfd_ida, 0, 0, GFP_KERNEL); diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h index fa0a524baed0..1a11ebbd74a9 100644 --- a/include/linux/eventfd.h +++ b/include/linux/eventfd.h @@ -45,10 +45,7 @@ void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt); DECLARE_PER_CPU(int, eventfd_wake_count); -static inline bool eventfd_signal_count(void) -{ - return this_cpu_read(eventfd_wake_count); -} +bool eventfd_signal_count(struct eventfd_ctx *ctx); #else /* CONFIG_EVENTFD */