From patchwork Tue May 12 08:59:40 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 11542461 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 552F81668 for ; Tue, 12 May 2020 09:00:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 375C4214DB for ; Tue, 12 May 2020 09:00:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="LgQftZug" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729465AbgELJAP (ORCPT ); Tue, 12 May 2020 05:00:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42806 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1729457AbgELJAO (ORCPT ); Tue, 12 May 2020 05:00:14 -0400 Received: from mail-wr1-x441.google.com (mail-wr1-x441.google.com [IPv6:2a00:1450:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 48168C05BD0C for ; Tue, 12 May 2020 02:00:12 -0700 (PDT) Received: by mail-wr1-x441.google.com with SMTP id v12so14306026wrp.12 for ; Tue, 12 May 2020 02:00:12 -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=LgQftZug1+s6r/6sfV0w6yEj/NMgDnXPjQ9rogWtkgMYDejoFBo0bPnwGW56hu1d7I qs3FiIgJnTmbmBqRQhBg/d/9mf6F8tXHWnk5q6Y4hrcpMMBBXw0ZHjxKx/PXQDwpH8gi /lG4giH5AqDaIZXE6JQNuQUTWIUktkeQZkN8E= 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=EqAq2wGskzVHQGw1sYfIybsxSd79ZSBNJCQU4Dp39EisMROnlu2KPBfQL262pfowjW PCHnuPtre6Y4DWxJHZjseAFOEGHVyPt5/kob8Y0/s9mTysrb6BeBSLka+ymzcsAwr5Bs Kx6Rv9n/rDRQO5bhWjSHOCRmnvN2IkCAFsLeeoHAc+/XVHrjj+8TUOxLfGJEQiUpS9Ki 9h9CtHpPVzlYRb+n6K9/WsPccz1S8LoaY3rJpqr/MvBiNi2nh5+5D+Gfu2xjBdbCALtG dla9YkpM356X+h+/sgF4z/hSAPRHSwntwJEHbaHiIE5W1SI1+Cd1UFr+Da641XFSWJpM 2L8w== X-Gm-Message-State: AGi0PubYZ1+cTYpJquQA2v/MsSGu6HoaWenuWnZD1gwiJuGXq/UtHVte 6w1x91aHMrJ9fApGrEIVRIcOvQ== X-Google-Smtp-Source: APiQypIHDkKnk39vr0THs9MDd2lPRfxpCvBWLiPU8TBM9Ly4fBvHufkGUrgX+LdKysku7drbWjQ/Mg== X-Received: by 2002:a5d:68c7:: with SMTP id p7mr25405016wrw.29.1589274010831; Tue, 12 May 2020 02:00:10 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id y10sm18845457wrd.95.2020.05.12.02.00.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 May 2020 02:00:10 -0700 (PDT) From: Daniel Vetter To: DRI Development Cc: LKML , Daniel Vetter , linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, Chris Wilson , Maarten Lankhorst , =?utf-8?q?Christian_?= =?utf-8?q?K=C3=B6nig?= , Daniel Vetter Subject: [RFC 13/17] drm/scheduler: use dma-fence annotations in tdr work Date: Tue, 12 May 2020 10:59:40 +0200 Message-Id: <20200512085944.222637-14-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200512085944.222637-1-daniel.vetter@ffwll.ch> References: <20200512085944.222637-1-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 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); } /**