From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f73.google.com (mail-ej1-f73.google.com [209.85.218.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2DF2130648C for ; Wed, 10 Sep 2025 06:39:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757486390; cv=none; b=ej06bKN0GDmyb8nyVQfKr8cztlpG1fSuL8LVdnQt2KMNDofzweRQ2lo+VU9gboc5IlqGmEbrHxcon2HRIjP9+wBMP12tvdEaFa/EtMUfOypeo/RABnBuC8JBESU3LvjUwTp3+yuokcx1ySIBzmQgiBxYFVGp3T51ARkAmFD4PZY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757486390; c=relaxed/simple; bh=rfQe+ePDp4Zo0AgaP4d2M/YN/CS2BDKY5Aq9m9aG2wI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=SZ55NFgF2vauht9RhP39MYVMSUcNiAxBoILX96canuIZOyGPfcUmhJbcIRo6l5nPPJq/AdHUreeW1kz10gbjsXl11pVGrny+5weporbQrx0UYlUGgsBuOrIsAZ57Twm8d4kkYFzC609+l0gJA4Pxe2/7Smajru9h2z5PZhZpmJQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=sfA9CzK1; arc=none smtp.client-ip=209.85.218.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="sfA9CzK1" Received: by mail-ej1-f73.google.com with SMTP id a640c23a62f3a-b046fc9f28bso554960466b.0 for ; Tue, 09 Sep 2025 23:39:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1757486387; x=1758091187; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=0ZgO5jwANFMehJfMoLYUsZTxd5NY3ndlOci6BOUflzQ=; b=sfA9CzK13Vexf+5Y5pM3KwocHcTeSTzAoISTLeF2IRgev8EvfJ/Y+XOsZMmwq80ma/ t7gHyDuaWeeVXSDmViqqjkfjYkMFkxJ2NSxMBAq9ALlqRQkGDV6mbYibUYZEoDZCdikw ixM0gc1hIizGNhaC9uw2PAwAfwKLlcNpV8vSY2Xl0v+25YBraocT2/Zb+mbeiMrLsojj hH5HANPsWyYf4CX/P3r+pMKCQbPbAw+u/I6810PyENH5LZs6nWGItNAdYGpIhTLfgUpQ cCC/iS/Mj1IQCWA6FjsNsj+O9v4B6JX6lwnkSDG/o8naR4oyB99VjwqcW/2npXMYxX1S frfQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1757486387; x=1758091187; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=0ZgO5jwANFMehJfMoLYUsZTxd5NY3ndlOci6BOUflzQ=; b=C5y5xqHA7Ws4CPyAux7CEfMcluGBFJd/wUo5D68R77Y7OhNZE9ZYEsLbYsvjWvnzXy 55phVdRoTOIrM3Jo+Grtr/Cw9fknrS0iZp3umNBiGxBlzViv1FVLJsqmU3hwjPImbb2m nMt0mXbC8GsWkJrCKtaX7hpM8G8LFRbFACbLBS3/xKL3EOiEtvLCKFo+UMB141fcTTDj kYZBR7xA1c3+gYh6TxKLvPecJFMANA09C+q1FPzbRv8BHbsiSQKDlwAEW84EpMlgmK5Y ErMTBfdaGPNYlQgaNJCi3CLeqTN32NtQV0JPPMxZGvsfN1+++0aFFJP59bawJUkzLxLD iblQ== X-Forwarded-Encrypted: i=1; AJvYcCV0WpeXpdciOmgPtoDWPy6aeEiOoXYO4O0bUBjQUXqmflRdT8fmwNbfwR5OgfQR72ZeX2okvIqOfUqcQqRmVw==@vger.kernel.org X-Gm-Message-State: AOJu0YwhelvbfiQDThws0aYhb48U0j+2yuSPG0dLscyGXxL5GXtVirc4 zfRrmYH4b4BN9l+mqk1gO3Wr4R/g7kCu4HU+1xn+bLSISjdTyvBPSeKVpn2e4eZc/55ER/DKgj8 BsgdL/fSeJtSfEpYlgg== X-Google-Smtp-Source: AGHT+IF290sfWDJWyXR0CbzZnHAG1Yyq7SWKBAx8oPF32kqB1mi5kcbwO1hzeAGXP44801EWVIisUmt4Rpwov5g= X-Received: from edh22.prod.google.com ([2002:a05:6402:5056:b0:62b:f094:4936]) (user=aliceryhl job=prod-delivery.src-stubby-dispatcher) by 2002:a17:907:3f2a:b0:b04:9d90:a7e6 with SMTP id a640c23a62f3a-b04b1741ac2mr1432308366b.55.1757486387560; Tue, 09 Sep 2025 23:39:47 -0700 (PDT) Date: Wed, 10 Sep 2025 06:39:46 +0000 In-Reply-To: Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250909-vmbo-defer-v2-0-9835d7349089@google.com> <20250909-vmbo-defer-v2-1-9835d7349089@google.com> Message-ID: Subject: Re: [PATCH v2 1/2] drm/gpuvm: add deferred vm_bo cleanup From: Alice Ryhl To: "Thomas =?utf-8?Q?Hellstr=C3=B6m?=" Cc: Danilo Krummrich , Matthew Brost , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Boris Brezillon , Steven Price , Daniel Almeida , Liviu Dudau , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Tue, Sep 09, 2025 at 04:20:32PM +0200, Thomas Hellstr=C3=B6m wrote: > On Tue, 2025-09-09 at 13:36 +0000, Alice Ryhl wrote: > > When using GPUVM in immediate mode, it is necessary to call > > drm_gpuvm_unlink() from the fence signalling critical path. However, > > unlink may call drm_gpuvm_bo_put(), which causes some challenges: > >=20 > > 1. drm_gpuvm_bo_put() often requires you to take resv locks, which > > you > > =C2=A0=C2=A0 can't do from the fence signalling critical path. > > 2. drm_gpuvm_bo_put() calls drm_gem_object_put(), which is often > > going > > =C2=A0=C2=A0 to be unsafe to call from the fence signalling critical pa= th. > >=20 > > To solve these issues, add a deferred version of drm_gpuvm_unlink() > > that > > adds the vm_bo to a deferred cleanup list, and then clean it up > > later. > >=20 > > The new methods take the GEMs GPUVA lock internally rather than > > letting > > the caller do it because it also needs to perform an operation after > > releasing the mutex again. This is to prevent freeing the GEM while > > holding the mutex (more info as comments in the patch). This means > > that > > the new methods can only be used with DRM_GPUVM_IMMEDIATE_MODE. > >=20 > > Signed-off-by: Alice Ryhl > > --- > > =C2=A0drivers/gpu/drm/drm_gpuvm.c | 174 > > ++++++++++++++++++++++++++++++++++++++++++++ > > =C2=A0include/drm/drm_gpuvm.h=C2=A0=C2=A0=C2=A0=C2=A0 |=C2=A0 26 ++++++= + > > =C2=A02 files changed, 200 insertions(+) > >=20 > > diff --git a/drivers/gpu/drm/drm_gpuvm.c > > b/drivers/gpu/drm/drm_gpuvm.c > > index > > 78a1a4f095095e9379bdf604d583f6c8b9863ccb..5aa8b3813019705f70101950af2 > > d8fe4e648e9d0 100644 > > --- a/drivers/gpu/drm/drm_gpuvm.c > > +++ b/drivers/gpu/drm/drm_gpuvm.c > > @@ -876,6 +876,27 @@ __drm_gpuvm_bo_list_add(struct drm_gpuvm *gpuvm, > > spinlock_t *lock, > > =C2=A0 cond_spin_unlock(lock, !!lock); > > =C2=A0} > > =C2=A0 > > +/** > > + * drm_gpuvm_bo_is_dead() - check whether this vm_bo is scheduled >=20 > NIT: Is zombie a better name than dead? I could see that name make sense. > > =C2=A0/** > > =C2=A0 * drm_gpuvm_bo_list_add() - insert a vm_bo into the given list > > =C2=A0 * @__vm_bo: the &drm_gpuvm_bo > > @@ -1081,6 +1102,9 @@ drm_gpuvm_init(struct drm_gpuvm *gpuvm, const > > char *name, > > =C2=A0 INIT_LIST_HEAD(&gpuvm->evict.list); > > =C2=A0 spin_lock_init(&gpuvm->evict.lock); > > =C2=A0 > > + INIT_LIST_HEAD(&gpuvm->bo_defer.list); > > + spin_lock_init(&gpuvm->bo_defer.lock); > > + >=20 > This list appears to exactly follow the pattern a lockless list was > designed for. Saves some space in the vm_bo and gets rid of the > excessive locking. Good point. Alice