From patchwork Thu Jun 4 08:12:20 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 11587409 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 F202E90 for ; Thu, 4 Jun 2020 08:13:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D4501207DA for ; Thu, 4 Jun 2020 08:13:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="MQtZQlsV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728016AbgFDINU (ORCPT ); Thu, 4 Jun 2020 04:13:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51512 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727779AbgFDIMv (ORCPT ); Thu, 4 Jun 2020 04:12:51 -0400 Received: from mail-wr1-x444.google.com (mail-wr1-x444.google.com [IPv6:2a00:1450:4864:20::444]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 633D0C08C5C5 for ; Thu, 4 Jun 2020 01:12:51 -0700 (PDT) Received: by mail-wr1-x444.google.com with SMTP id t18so5046131wru.6 for ; Thu, 04 Jun 2020 01:12:51 -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=cSDqH5ij1BPhN02yjRk7X7Ch94EKjTTeY1hANr+YPIg=; b=MQtZQlsVT4D6M/TZ/TTIidOW50d1o6Q0AiFZHAR30zUPft45srmFqn7Q/chHCQgEwb QuUQyDP7PvsPZgFWkvGTZI4QJxfIwFPjWqa5WQ26vsMQBqacHIfA9jXi1YXDD4rvkBs/ wmbeqc0eo5WnTY22+0zRQvessA2Qhc3AShHpw= 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=cSDqH5ij1BPhN02yjRk7X7Ch94EKjTTeY1hANr+YPIg=; b=OX+/lRUouI2T4n3pamDQINjgrara7cOqLBxirAhfT1a3aDTxg7FvNn0QUMPeX2BTLX nz2WlnGTZya6JJ0c00fSQ0KtTi0nptnNxe8a5wq8vYFhDv54oQf7vAL1BhqCu8h92l4b DlVepD+fo4gvJnnZLn7nWns/tiQvHG5Cm2FRFhHXYEQXcB0putsxdJa/0BKQrYZHAO6I SChU9gka404mae7LbCaDCKaJ2//nLC+ETD/kYVJC/7QxrJgOgZV48DWXTqCz8nMouu/1 z0ASWdfIkws4EOUL+sJpI+wJbUgrJH2GD4p8EY48UAWOyCgtfxu64c26/TrvP0Dq3VhB bZ9Q== X-Gm-Message-State: AOAM533nOLHws7KSUovdyNjvzaIZHNftCbztHMG0ofzJTXLwrFAprwzn BXgucpNfTrAXYQeSRqav76ZBdQ== X-Google-Smtp-Source: ABdhPJwTJtq4ZMbXkz9yUomRGTcjfw0qYxpotGG6g0Tb3unDYU1epqhHkACAq8ejGSpX2fZsvYsoJQ== X-Received: by 2002:a05:6000:7:: with SMTP id h7mr3471787wrx.55.1591258370059; Thu, 04 Jun 2020 01:12:50 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id f11sm6873305wrj.2.2020.06.04.01.12.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Jun 2020 01:12:49 -0700 (PDT) From: Daniel Vetter To: DRI Development Cc: Intel Graphics Development , LKML , linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org, Daniel Vetter , linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, Chris Wilson , Maarten Lankhorst , =?utf-8?q?Christian_?= =?utf-8?q?K=C3=B6nig?= , Daniel Vetter Subject: [PATCH 14/18] drm/scheduler: use dma-fence annotations in tdr work Date: Thu, 4 Jun 2020 10:12:20 +0200 Message-Id: <20200604081224.863494-15-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200604081224.863494-1-daniel.vetter@ffwll.ch> References: <20200604081224.863494-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org In the face of unpriviledged userspace being able to submit bogus gpu workloads the kernel needs gpu timeout and reset (tdr) to guarantee that dma_fences actually complete. Annotate this worker to make sure we don't have any accidental locking inversions or other problems lurking. Originally this was part of the overall scheduler annotation patch. But amdgpu has some glorious inversions here: - grabs console_lock - does a full modeset, which grabs all kinds of locks (drm_modeset_lock, dma_resv_lock) which can deadlock with dma_fence_wait held inside them. - almost minor at that point, but the modeset code also allocates memory These all look like they'll be very hard to fix properly, the hardware seems to require a full display reset with any gpu recovery. Hence split out as a seperate patch. Since amdgpu isn't the only hardware driver that needs to reset the display (at least gen2/3 on intel have the same problem) we need a generic solution for this. There's two tricks we could still from drm/i915 and lift to dma-fence: - The big whack, aka force-complete all fences. i915 does this for all pending jobs if the reset is somehow stuck. Trouble is we'd need to do this for all fences in the entire system, and just the book-keeping for that will be fun. Plus lots of drivers use fences for all kinds of internal stuff like memory management, so unconditionally resetting all of them doesn't work. I'm also hoping that with these fence annotations we could enlist lockdep in finding the last offenders causing deadlocks, and we could remove this get-out-of-jail trick. - The more feasible approach (across drivers at least as part of the dma_fence contract) is what drm/i915 does for gen2/3: When we need to reset the display we wake up all dma_fence_wait_interruptible calls, or well at least the equivalent of those in i915 internally. Relying on ioctl restart we force all other threads to release their locks, which means the tdr thread is guaranteed to be able to get them. I think we could implement this at the dma_fence level, including proper lockdep annotations. dma_fence_begin_tdr(): - must be nested within a dma_fence_begin/end_signalling section - will wake up all interruptible (but not the non-interruptible) dma_fence_wait() calls and force them to complete with a -ERESTARTSYS errno code. All new interrupitble calls to dma_fence_wait() will immeidately fail with the same error code. dma_fence_end_trdr(): - this will convert dma_fence_wait() calls back to normal. Of course interrupting dma_fence_wait is only ok if the caller specified that, which means we need to split the annotations into interruptible and non-interruptible version. If we then make sure that we only use interruptible dma_fence_wait() calls while holding drm_modeset_lock we can grab them in tdr code, and allow display resets. Doing the same for dma_resv_lock might be a lot harder, so buffer updates must be avoided. What's worse, we're not going to be able to make the dma_fence_wait calls in mmu-notifiers interruptible, that doesn't work. So allocating memory still wont' be allowed, even in tdr sections. Plus obviously we can use this trick only in tdr, it is rather intrusive. 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 --- drivers/gpu/drm/scheduler/sched_main.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c index 06a736e506ad..e34a44376e87 100644 --- a/drivers/gpu/drm/scheduler/sched_main.c +++ b/drivers/gpu/drm/scheduler/sched_main.c @@ -279,9 +279,12 @@ static void drm_sched_job_timedout(struct work_struct *work) { struct drm_gpu_scheduler *sched; struct drm_sched_job *job; + bool fence_cookie; sched = container_of(work, struct drm_gpu_scheduler, work_tdr.work); + fence_cookie = dma_fence_begin_signalling(); + /* Protects against concurrent deletion in drm_sched_get_cleanup_job */ spin_lock(&sched->job_list_lock); job = list_first_entry_or_null(&sched->ring_mirror_list, @@ -313,6 +316,8 @@ static void drm_sched_job_timedout(struct work_struct *work) spin_lock(&sched->job_list_lock); drm_sched_start_timeout(sched); spin_unlock(&sched->job_list_lock); + + dma_fence_end_signalling(fence_cookie); } /**