From patchwork Fri Jun 12 07:01:04 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 11601305 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 CB535138C for ; Fri, 12 Jun 2020 07:01:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ADBAF20801 for ; Fri, 12 Jun 2020 07:01:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="Z/0PZJen" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726364AbgFLHBQ (ORCPT ); Fri, 12 Jun 2020 03:01:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43302 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726287AbgFLHBP (ORCPT ); Fri, 12 Jun 2020 03:01:15 -0400 Received: from mail-wm1-x341.google.com (mail-wm1-x341.google.com [IPv6:2a00:1450:4864:20::341]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8F38BC08C5C1 for ; Fri, 12 Jun 2020 00:01:13 -0700 (PDT) Received: by mail-wm1-x341.google.com with SMTP id u13so7073970wml.1 for ; Fri, 12 Jun 2020 00:01:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=mwb5lgpix4XST2DTfjgAUf64Z8hdMDaqX2rqhJ09+Dc=; b=Z/0PZJenemEubopMdJxXwCvFPmitS5sp/UJwCCmirspo81er4XWRzvTWGAvd2s9iVi bYVp1SG0UQK4AfZtyeTwGO6+q3A3rAwk9hrgQScpVHsnLxjxkAURJM9DwCyP8raHfOGR 7WgNqH8c9EjkqHvSLazvcH8b7u3A8RrAuj6Ww= 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=mwb5lgpix4XST2DTfjgAUf64Z8hdMDaqX2rqhJ09+Dc=; b=TU/OcVjHDl53ybQb9g5NkCFHTMWKQsVONNnxFvrymf+Eq9zYNFwwCkIA7q+JFdt6a1 G45TtJ8pasnY0WuqrA8O01w3ykUZUi0kGUN2iZZ1+Ak7uMlF9QaaqZ3tuK4/fHSS883b mScG8cxVMMrCXP52Y/5rGJNOM1XO0pEmavlcM20yzGLJHs817cesRWbasOIR2bCZowyW m7xgkeE7y6f98oc3eK1nKZYcHROYQZPPMlAlVpSgmyWW4UONuCp1RB030Fu0CM8wL0o4 6hUyvHBFpNRysjfNOvyecF6miCe2CNIONoqILDUE2pdIrvSXLp3I3uIFaA5D8/diGeEZ ReHg== X-Gm-Message-State: AOAM533NI+W8TVaq+7X7dFev512I0dWgMhY6OLlZT7g6o3xO2CLhtbSR NCcBCxbuNsScn21/leJnijfFdQ== X-Google-Smtp-Source: ABdhPJwwh20KqP8ubgxA8aiC04aO22feyqX8T0rjSDRNgUxaOSxk42eulIqfnoix/xEi29+H7leXtw== X-Received: by 2002:a1c:9ec5:: with SMTP id h188mr11662120wme.9.1591945270420; Fri, 12 Jun 2020 00:01:10 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id c5sm9401610wrb.72.2020.06.12.00.01.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Jun 2020 00:01:09 -0700 (PDT) From: Daniel Vetter To: DRI Development Cc: Intel Graphics Development , Daniel Vetter , kernel test robot , =?utf-8?q?Thomas_Hellstr=C3=B6m?= , Mika Kuoppala , linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org, Chris Wilson , Maarten Lankhorst , =?utf-8?q?Christian_?= =?utf-8?q?K=C3=B6nig?= , Daniel Vetter Subject: [PATCH] dma-fence: prime lockdep annotations Date: Fri, 12 Jun 2020 09:01:04 +0200 Message-Id: <20200612070104.1777608-1-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200604081224.863494-5-daniel.vetter@ffwll.ch> References: <20200604081224.863494-5-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Two in one go: - it is allowed to call dma_fence_wait() while holding a dma_resv_lock(). This is fundamental to how eviction works with ttm, so required. - it is allowed to call dma_fence_wait() from memory reclaim contexts, specifically from shrinker callbacks (which i915 does), and from mmu notifier callbacks (which amdgpu does, and which i915 sometimes also does, and probably always should, but that's kinda a debate). Also for stuff like HMM we really need to be able to do this, or things get real dicey. Consequence is that any critical path necessary to get to a dma_fence_signal for a fence must never a) call dma_resv_lock nor b) allocate memory with GFP_KERNEL. Also by implication of dma_resv_lock(), no userspace faulting allowed. That's some supremely obnoxious limitations, which is why we need to sprinkle the right annotations to all relevant paths. The one big locking context we're leaving out here is mmu notifiers, added in commit 23b68395c7c78a764e8963fc15a7cfd318bf187f Author: Daniel Vetter Date: Mon Aug 26 22:14:21 2019 +0200 mm/mmu_notifiers: add a lockdep map for invalidate_range_start/end that one covers a lot of other callsites, and it's also allowed to wait on dma-fences from mmu notifiers. But there's no ready-made functions exposed to prime this, so I've left it out for now. v2: Also track against mmu notifier context. v3: kerneldoc to spec the cross-driver contract. Note that currently i915 throws in a hard-coded 10s timeout on foreign fences (not sure why that was done, but it's there), which is why that rule is worded with SHOULD instead of MUST. Also some of the mmu_notifier/shrinker rules might surprise SoC drivers, I haven't fully audited them all. Which is infeasible anyway, we'll need to run them with lockdep and dma-fence annotations and see what goes boom. v4: A spelling fix from Mika v5: #ifdef for CONFIG_MMU_NOTIFIER. Reported by 0day. Unfortunately this means lockdep enforcement is slightly inconsistent, it won't spot GFP_NOIO and GFP_NOFS allocations in the wrong spot if CONFIG_MMU_NOTIFIER is disabled in the kernel config. Oh well. Cc: kernel test robot Reviewed-by: Thomas Hellström (v4) Cc: Mika Kuoppala Cc: Thomas Hellstrom Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Cc: linux-rdma@vger.kernel.org Cc: amd-gfx@lists.freedesktop.org Cc: intel-gfx@lists.freedesktop.org Cc: Chris Wilson Cc: Maarten Lankhorst Cc: Christian König Signed-off-by: Daniel Vetter --- Documentation/driver-api/dma-buf.rst | 6 ++++ drivers/dma-buf/dma-fence.c | 41 ++++++++++++++++++++++++++++ drivers/dma-buf/dma-resv.c | 8 ++++++ include/linux/dma-fence.h | 1 + 4 files changed, 56 insertions(+) diff --git a/Documentation/driver-api/dma-buf.rst b/Documentation/driver-api/dma-buf.rst index 05d856131140..f8f6decde359 100644 --- a/Documentation/driver-api/dma-buf.rst +++ b/Documentation/driver-api/dma-buf.rst @@ -133,6 +133,12 @@ DMA Fences .. kernel-doc:: drivers/dma-buf/dma-fence.c :doc: DMA fences overview +DMA Fence Cross-Driver Contract +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +.. kernel-doc:: drivers/dma-buf/dma-fence.c + :doc: fence cross-driver contract + DMA Fence Signalling Annotations ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c index 0005bc002529..754e6fb84fb7 100644 --- a/drivers/dma-buf/dma-fence.c +++ b/drivers/dma-buf/dma-fence.c @@ -64,6 +64,47 @@ static atomic64_t dma_fence_context_counter = ATOMIC64_INIT(1); * &dma_buf.resv pointer. */ +/** + * DOC: fence cross-driver contract + * + * Since &dma_fence provide a cross driver contract, all drivers must follow the + * same rules: + * + * * Fences must complete in a reasonable time. Fences which represent kernels + * and shaders submitted by userspace, which could run forever, must be backed + * up by timeout and gpu hang recovery code. Minimally that code must prevent + * further command submission and force complete all in-flight fences, e.g. + * when the driver or hardware do not support gpu reset, or if the gpu reset + * failed for some reason. Ideally the driver supports gpu recovery which only + * affects the offending userspace context, and no other userspace + * submissions. + * + * * Drivers may have different ideas of what completion within a reasonable + * time means. Some hang recovery code uses a fixed timeout, others a mix + * between observing forward progress and increasingly strict timeouts. + * Drivers should not try to second guess timeout handling of fences from + * other drivers. + * + * * To ensure there's no deadlocks of dma_fence_wait() against other locks + * drivers should annotate all code required to reach dma_fence_signal(), + * which completes the fences, with dma_fence_begin_signalling() and + * dma_fence_end_signalling(). + * + * * Drivers are allowed to call dma_fence_wait() while holding dma_resv_lock(). + * This means any code required for fence completion cannot acquire a + * &dma_resv lock. Note that this also pulls in the entire established + * locking hierarchy around dma_resv_lock() and dma_resv_unlock(). + * + * * Drivers are allowed to call dma_fence_wait() from their &shrinker + * callbacks. This means any code required for fence completion cannot + * allocate memory with GFP_KERNEL. + * + * * Drivers are allowed to call dma_fence_wait() from their &mmu_notifier + * respectively &mmu_interval_notifier callbacks. This means any code required + * for fence completeion cannot allocate memory with GFP_NOFS or GFP_NOIO. + * Only GFP_ATOMIC is permissible, which might fail. + */ + static const char *dma_fence_stub_get_name(struct dma_fence *fence) { return "stub"; diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c index 99c0a33c918d..51f0583ead19 100644 --- a/drivers/dma-buf/dma-resv.c +++ b/drivers/dma-buf/dma-resv.c @@ -35,6 +35,7 @@ #include #include #include +#include /** * DOC: Reservation Object Overview @@ -115,6 +116,13 @@ static int __init dma_resv_lockdep(void) if (ret == -EDEADLK) dma_resv_lock_slow(&obj, &ctx); fs_reclaim_acquire(GFP_KERNEL); +#ifdef CONFIG_MMU_NOTIFIER + lock_map_acquire(&__mmu_notifier_invalidate_range_start_map); + __dma_fence_might_wait(); + lock_map_release(&__mmu_notifier_invalidate_range_start_map); +#else + __dma_fence_might_wait(); +#endif fs_reclaim_release(GFP_KERNEL); ww_mutex_unlock(&obj.lock); ww_acquire_fini(&ctx); diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h index 3f288f7db2ef..09e23adb351d 100644 --- a/include/linux/dma-fence.h +++ b/include/linux/dma-fence.h @@ -360,6 +360,7 @@ dma_fence_get_rcu_safe(struct dma_fence __rcu **fencep) #ifdef CONFIG_LOCKDEP bool dma_fence_begin_signalling(void); void dma_fence_end_signalling(bool cookie); +void __dma_fence_might_wait(void); #else static inline bool dma_fence_begin_signalling(void) {