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=-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 3AEF4C433E0 for ; Tue, 19 Jan 2021 08:42:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EA2ED23121 for ; Tue, 19 Jan 2021 08:41:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727933AbhASFVr (ORCPT ); Tue, 19 Jan 2021 00:21:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388564AbhASFGL (ORCPT ); Tue, 19 Jan 2021 00:06:11 -0500 Received: from mail-pf1-x42a.google.com (mail-pf1-x42a.google.com [IPv6:2607:f8b0:4864:20::42a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 83368C0613CF for ; Mon, 18 Jan 2021 21:04:38 -0800 (PST) Received: by mail-pf1-x42a.google.com with SMTP id i63so4441357pfg.7 for ; Mon, 18 Jan 2021 21:04:38 -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=W8y876Dbq8gZuEg5QYXKhKTizoMMwtFxcmKeIZtDQdx+XEt3dW/eHtSMhQvknQYW4K DnsCpn+GirhCRLFyk/uVDaIJoXZgyWsH6gU53zdrGPud9lsener1pfIQEwdiCZRktfE+ Ne1ZR7dli2HUDcE+3V2rbyvftav5V4WgBCwhpQ0bHoynV0GboyaGO/cjnRSZdzh0GmFw r/A5ZX/PxqxanTpbUqh+VaClMqoh4p4eePPZY6MRWFJ7BiyHJsTxQWwUiwGliuSOKvLc PCreg4kS3gTI+lm3d0KE5HrHAWJ4B0/fMhjVOWrn+u+7Kwg0P9wxlbpTSDhJDbdRaU+G Y9Jg== 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=CDJzaNB9y3wPQ8I8u97aaGnxL/8KfrXqCw1VOQLosxFy9WhCX3HJjgcdzdgDlBJi8q WhxyP6njlfH4yooV660b/F8GHAvchYzgbNlexnjPgODClNTOcMIJzYcanvArpS45dKKE WTOqrIHTxEqgF0tudAZcRszTnV3jNb02Jh6WrK4NE0tXDW6pC1mexk/U9jfA5O9g+rqq CFANBzjkSGszG3fpAmLfazwcXuSBAJe4c4xz4ycUuVnGz//SztJ2n7APLDC04b6PQ/KF ZqGz7TYqnbVQVt94z411KR1hXC8iqoSJEoto9CJtSX4NSAr81n0jyecukj1jIETdQ2eo OjlQ== X-Gm-Message-State: AOAM533kiUO/CuHUxcVdBW8/PjZZ20zZ6Wr1u7Rle/BJR24o2t7JIjx/ Bpe+fiIewRd39LUpeI7Knt2T X-Google-Smtp-Source: ABdhPJwhMmXGRAF9exzwdYFbs4DDh7HaNjaSgRVmLvyUt1TO1CzzbUW14r26LDKrseM7tbJ/BRrzFA== X-Received: by 2002:a62:ddcd:0:b029:1a6:99ff:a75e with SMTP id w196-20020a62ddcd0000b02901a699ffa75emr2486197pff.42.1611032678076; Mon, 18 Jan 2021 21:04:38 -0800 (PST) Received: from localhost ([139.177.225.243]) by smtp.gmail.com with ESMTPSA id gv22sm1047509pjb.56.2021.01.18.21.04.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Jan 2021 21:04:37 -0800 (PST) From: Xie Yongji To: mst@redhat.com, jasowang@redhat.com, stefanha@redhat.com, sgarzare@redhat.com, parav@nvidia.com, bob.liu@oracle.com, hch@infradead.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 Subject: [RFC v3 01/11] eventfd: track eventfd_signal() recursion depth separately in different cases Date: Tue, 19 Jan 2021 12:59:10 +0800 Message-Id: <20210119045920.447-2-xieyongji@bytedance.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210119045920.447-1-xieyongji@bytedance.com> References: <20210119045920.447-1-xieyongji@bytedance.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 */ -- 2.11.0