From patchwork Mon Jun 24 21:01:10 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jason Gunthorpe X-Patchwork-Id: 11014893 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A20AF14BB for ; Tue, 25 Jun 2019 07:29:18 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8CE8E1FE8B for ; Tue, 25 Jun 2019 07:29:18 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8032828AD9; Tue, 25 Jun 2019 07:29:18 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id DD91B1FE8B for ; Tue, 25 Jun 2019 07:29:17 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 07C0B89FEC; Tue, 25 Jun 2019 07:27:36 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mail-wm1-x342.google.com (mail-wm1-x342.google.com [IPv6:2a00:1450:4864:20::342]) by gabe.freedesktop.org (Postfix) with ESMTPS id 9826B89DE1 for ; Mon, 24 Jun 2019 21:02:08 +0000 (UTC) Received: by mail-wm1-x342.google.com with SMTP id u8so721112wmm.1 for ; Mon, 24 Jun 2019 14:02:08 -0700 (PDT) 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=S3r5edHB129w6+WHP2qce1cv++fCEyzuU0DGZG/FVjU=; b=nX/aCtVlA8NO1oQc9vTgf2kW8jf9GrnBaU5Q4cN+mbxTizC7A1E0039Hl+KM5u3BSl YsZw7v+/0B046dk8h7pEfbZ24wQzJhNGoeZSt/Tq5BhTrNzfb4bYpNeGBFZ/PLKX5PcE RDPhQdk+UX5sgtnkJqDF5vsV2ou5mc+Nv4Mannq7euIADZaQPALUHsYhxEmOHZojdhZo ZocFtIKHzxhRv3wLp8qD3fXEWw+NzQLOm3Xw0acIxo1To2fPL2rYKJQEpygj9qMrx1Lt BYu4oq8FcpHW70rqiQvMJFitpLwrQ30eMBbWSgokqcZ9vqFRrnTLVTzlnyn+yVL8oUYj pT2A== X-Gm-Message-State: APjAAAWbcC5jmduo9/VX36Q8a44LwSuZa+XFb1aJyfehNbMDeAfkwSNd cEr1hmp9wOuPn3EN3kZLJ7jXTQ== X-Google-Smtp-Source: APXvYqyInST0pwmwLzJ/uxOPmS6zD6FzKVUhnIxI9FAO5JkPPLVhNSreFOU/LTKh9NST5RUcH7Pi3Q== X-Received: by 2002:a1c:3:: with SMTP id 3mr16798813wma.6.1561410127205; Mon, 24 Jun 2019 14:02:07 -0700 (PDT) Received: from ziepe.ca ([66.187.232.66]) by smtp.gmail.com with ESMTPSA id l4sm411869wmh.18.2019.06.24.14.02.02 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 24 Jun 2019 14:02:02 -0700 (PDT) Received: from jgg by jggl.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1hfW6D-0001N7-5h; Mon, 24 Jun 2019 18:02:01 -0300 From: Jason Gunthorpe To: Jerome Glisse , Ralph Campbell , John Hubbard , Felix.Kuehling@amd.com Subject: [PATCH v4 hmm 12/12] mm/hmm: Fix error flows in hmm_invalidate_range_start Date: Mon, 24 Jun 2019 18:01:10 -0300 Message-Id: <20190624210110.5098-13-jgg@ziepe.ca> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190624210110.5098-1-jgg@ziepe.ca> References: <20190624210110.5098-1-jgg@ziepe.ca> MIME-Version: 1.0 X-Mailman-Approved-At: Tue, 25 Jun 2019 07:27:07 +0000 X-Mailman-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=S3r5edHB129w6+WHP2qce1cv++fCEyzuU0DGZG/FVjU=; b=hxllCZWingbWA/f5vgNASI2pGcmQkq+YMV0+41KqM+6SHez+NGQ1uJO082ws99YMd9 a02GfWbWiybTgkW5XKpp58ScKdfgpRyQkF+lx8bQgY/E0sad83Uy5xKeM+5fDXk5l+dn kREAcw817qhEHGbJzh/JPNg+S+obDw/5JZAk7sJkD1VoJOjy+A9WMNZt4hUg76s0LIwA 7CnwGTdpr/y52OLSiCtTuB/yhZqVQPS2pkaGeOalh4K4i+1u3/L+S9jsgkydPV6oBOsv +C7ZAWxMOYu5gNiQFVoJHSQaBp2JqH18fs4FjehP3vhAnvD2AIJi3c1yJBiWTS4qwHYX +fIw== X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrea Arcangeli , Philip Yang , linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org, linux-mm@kvack.org, Jason Gunthorpe , dri-devel@lists.freedesktop.org, Ira Weiny , Christoph Hellwig , Ben Skeggs Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP From: Jason Gunthorpe If the trylock on the hmm->mirrors_sem fails the function will return without decrementing the notifiers that were previously incremented. Since the caller will not call invalidate_range_end() on EAGAIN this will result in notifiers becoming permanently incremented and deadlock. If the sync_cpu_device_pagetables() required blocking the function will not return EAGAIN even though the device continues to touch the pages. This is a violation of the mmu notifier contract. Switch, and rename, the ranges_lock to a spin lock so we can reliably obtain it without blocking during error unwind. The error unwind is necessary since the notifiers count must be held incremented across the call to sync_cpu_device_pagetables() as we cannot allow the range to become marked valid by a parallel invalidate_start/end() pair while doing sync_cpu_device_pagetables(). Signed-off-by: Jason Gunthorpe Reviewed-by: Ralph Campbell Reviewed-by: Christoph Hellwig Tested-by: Philip Yang Signed-off-by: Jason Gunthorpe Reviewed-by: Ralph Campbell Reviewed-by: Christoph Hellwig Tested-by: Philip Yang --- include/linux/hmm.h | 2 +- mm/hmm.c | 72 +++++++++++++++++++++++++++------------------ 2 files changed, 45 insertions(+), 29 deletions(-) diff --git a/include/linux/hmm.h b/include/linux/hmm.h index bf013e96525771..0fa8ea34ccef6d 100644 --- a/include/linux/hmm.h +++ b/include/linux/hmm.h @@ -86,7 +86,7 @@ struct hmm { struct mm_struct *mm; struct kref kref; - struct mutex lock; + spinlock_t ranges_lock; struct list_head ranges; struct list_head mirrors; struct mmu_notifier mmu_notifier; diff --git a/mm/hmm.c b/mm/hmm.c index b224ea635a7716..89549eac03d506 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -64,7 +64,7 @@ static struct hmm *hmm_get_or_create(struct mm_struct *mm) init_rwsem(&hmm->mirrors_sem); hmm->mmu_notifier.ops = NULL; INIT_LIST_HEAD(&hmm->ranges); - mutex_init(&hmm->lock); + spin_lock_init(&hmm->ranges_lock); kref_init(&hmm->kref); hmm->notifiers = 0; hmm->mm = mm; @@ -144,6 +144,23 @@ static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm) hmm_put(hmm); } +static void notifiers_decrement(struct hmm *hmm) +{ + lockdep_assert_held(&hmm->ranges_lock); + + hmm->notifiers--; + if (!hmm->notifiers) { + struct hmm_range *range; + + list_for_each_entry(range, &hmm->ranges, list) { + if (range->valid) + continue; + range->valid = true; + } + wake_up_all(&hmm->wq); + } +} + static int hmm_invalidate_range_start(struct mmu_notifier *mn, const struct mmu_notifier_range *nrange) { @@ -151,6 +168,7 @@ static int hmm_invalidate_range_start(struct mmu_notifier *mn, struct hmm_mirror *mirror; struct hmm_update update; struct hmm_range *range; + unsigned long flags; int ret = 0; if (!kref_get_unless_zero(&hmm->kref)) @@ -161,12 +179,7 @@ static int hmm_invalidate_range_start(struct mmu_notifier *mn, update.event = HMM_UPDATE_INVALIDATE; update.blockable = mmu_notifier_range_blockable(nrange); - if (mmu_notifier_range_blockable(nrange)) - mutex_lock(&hmm->lock); - else if (!mutex_trylock(&hmm->lock)) { - ret = -EAGAIN; - goto out; - } + spin_lock_irqsave(&hmm->ranges_lock, flags); hmm->notifiers++; list_for_each_entry(range, &hmm->ranges, list) { if (update.end < range->start || update.start >= range->end) @@ -174,7 +187,7 @@ static int hmm_invalidate_range_start(struct mmu_notifier *mn, range->valid = false; } - mutex_unlock(&hmm->lock); + spin_unlock_irqrestore(&hmm->ranges_lock, flags); if (mmu_notifier_range_blockable(nrange)) down_read(&hmm->mirrors_sem); @@ -182,16 +195,26 @@ static int hmm_invalidate_range_start(struct mmu_notifier *mn, ret = -EAGAIN; goto out; } + list_for_each_entry(mirror, &hmm->mirrors, list) { - int ret; + int rc; - ret = mirror->ops->sync_cpu_device_pagetables(mirror, &update); - if (!update.blockable && ret == -EAGAIN) + rc = mirror->ops->sync_cpu_device_pagetables(mirror, &update); + if (rc) { + if (WARN_ON(update.blockable || rc != -EAGAIN)) + continue; + ret = -EAGAIN; break; + } } up_read(&hmm->mirrors_sem); out: + if (ret) { + spin_lock_irqsave(&hmm->ranges_lock, flags); + notifiers_decrement(hmm); + spin_unlock_irqrestore(&hmm->ranges_lock, flags); + } hmm_put(hmm); return ret; } @@ -200,23 +223,14 @@ static void hmm_invalidate_range_end(struct mmu_notifier *mn, const struct mmu_notifier_range *nrange) { struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier); + unsigned long flags; if (!kref_get_unless_zero(&hmm->kref)) return; - mutex_lock(&hmm->lock); - hmm->notifiers--; - if (!hmm->notifiers) { - struct hmm_range *range; - - list_for_each_entry(range, &hmm->ranges, list) { - if (range->valid) - continue; - range->valid = true; - } - wake_up_all(&hmm->wq); - } - mutex_unlock(&hmm->lock); + spin_lock_irqsave(&hmm->ranges_lock, flags); + notifiers_decrement(hmm); + spin_unlock_irqrestore(&hmm->ranges_lock, flags); hmm_put(hmm); } @@ -868,6 +882,7 @@ int hmm_range_register(struct hmm_range *range, { unsigned long mask = ((1UL << page_shift) - 1UL); struct hmm *hmm = mirror->hmm; + unsigned long flags; range->valid = false; range->hmm = NULL; @@ -886,7 +901,7 @@ int hmm_range_register(struct hmm_range *range, return -EFAULT; /* Initialize range to track CPU page table updates. */ - mutex_lock(&hmm->lock); + spin_lock_irqsave(&hmm->ranges_lock, flags); range->hmm = hmm; kref_get(&hmm->kref); @@ -898,7 +913,7 @@ int hmm_range_register(struct hmm_range *range, */ if (!hmm->notifiers) range->valid = true; - mutex_unlock(&hmm->lock); + spin_unlock_irqrestore(&hmm->ranges_lock, flags); return 0; } @@ -914,10 +929,11 @@ EXPORT_SYMBOL(hmm_range_register); void hmm_range_unregister(struct hmm_range *range) { struct hmm *hmm = range->hmm; + unsigned long flags; - mutex_lock(&hmm->lock); + spin_lock_irqsave(&hmm->ranges_lock, flags); list_del_init(&range->list); - mutex_unlock(&hmm->lock); + spin_unlock_irqrestore(&hmm->ranges_lock, flags); /* Drop reference taken by hmm_range_register() */ mmput(hmm->mm);