From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id AB345C433F5 for ; Wed, 2 Mar 2022 21:59:29 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7B40210E25C; Wed, 2 Mar 2022 21:59:26 +0000 (UTC) Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by gabe.freedesktop.org (Postfix) with ESMTPS id E485A10E4ED; Wed, 2 Mar 2022 21:59:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1646258365; x=1677794365; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=yawzHkXCNEi4OGTe3ZX3h2CkuTgqHVGcefmuT5KID7w=; b=F+YLpV5jfW4i2IZDDncHmV68nIu58aCh7JyMi8ymvprGXKrEJHsjJoMe IXLCKJNMTDWdhfWxsUcPnWB59z63Ay7uBzY2SVjQngtRaDKSGN3EI3UqN rDXPPpoSroqF5Ly8DUWo+K7V1AD3F5R88I/97yV6ldnAn1kNrgN+fG5YZ mUm9Ve7ffOqh+yWtdhLM106cTS0kPVlNt9xHHwzqmP4/gR7dVbHk2AO4Q RaOphA9t4wVEktr8GDbZ7YhoF20vDpJzdRsYuGq4wX5IetU7CltSwdpU0 w2zkk0KANFgIrBDKGfr58RmWqJg7i0ynlDkNwOAR/hr1WX1eUe0mkjALO A==; X-IronPort-AV: E=McAfee;i="6200,9189,10274"; a="237024883" X-IronPort-AV: E=Sophos;i="5.90,150,1643702400"; d="scan'208";a="237024883" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Mar 2022 13:59:24 -0800 X-IronPort-AV: E=Sophos;i="5.90,150,1643702400"; d="scan'208";a="641858442" Received: from nvishwa1-desk.sc.intel.com (HELO nvishwa1-DESK) ([172.25.29.76]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Mar 2022 13:59:24 -0800 Date: Wed, 2 Mar 2022 14:01:41 -0800 From: Niranjana Vishwanathapura To: Thomas =?iso-8859-1?Q?Hellstr=F6m?= Subject: Re: [PATCH v2 2/3] drm/i915: Remove the vma refcount Message-ID: <20220302220139.GH25117@nvishwa1-DESK> References: <20220302102200.158637-1-thomas.hellstrom@linux.intel.com> <20220302102200.158637-3-thomas.hellstrom@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220302102200.158637-3-thomas.hellstrom@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: intel-gfx@lists.freedesktop.org, matthew.auld@intel.com, dri-devel@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Wed, Mar 02, 2022 at 11:21:59AM +0100, Thomas Hellström wrote: >Now that i915_vma_parked() is taking the object lock on vma destruction, >and the only user of the vma refcount, i915_gem_object_unbind() >also takes the object lock, remove the vma refcount. > >Signed-off-by: Thomas Hellström >--- > drivers/gpu/drm/i915/i915_gem.c | 17 +++++++++++++---- > drivers/gpu/drm/i915/i915_vma.c | 14 +++----------- > drivers/gpu/drm/i915/i915_vma.h | 14 -------------- > drivers/gpu/drm/i915/i915_vma_types.h | 1 - > 4 files changed, 16 insertions(+), 30 deletions(-) > >diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c >index dd84ebabb50f..c26110abcc0b 100644 >--- a/drivers/gpu/drm/i915/i915_gem.c >+++ b/drivers/gpu/drm/i915/i915_gem.c >@@ -151,14 +151,25 @@ int i915_gem_object_unbind(struct drm_i915_gem_object *obj, > break; > } > >+ /* >+ * Requiring the vm destructor to take the object lock >+ * before destroying a vma would help us eliminate the >+ * i915_vm_tryget() here, AND thus also the barrier stuff >+ * at the end. That's an easy fix, but sleeping locks in >+ * a kthread should generally be avoided. >+ */ > ret = -EAGAIN; > if (!i915_vm_tryget(vma->vm)) > break; > >- /* Prevent vma being freed by i915_vma_parked as we unbind */ >- vma = __i915_vma_get(vma); > spin_unlock(&obj->vma.lock); > >+ /* >+ * Since i915_vma_parked() takes the object lock >+ * before vma destruction, it won't race us here, >+ * and destroy the vma from under us. >+ */ >+ > if (vma) { > bool vm_trylock = !!(flags & I915_GEM_OBJECT_UNBIND_VM_TRYLOCK); > ret = -EBUSY; >@@ -180,8 +191,6 @@ int i915_gem_object_unbind(struct drm_i915_gem_object *obj, > ret = i915_vma_unbind(vma); > } > } >- >- __i915_vma_put(vma); > } > > i915_vm_put(vma->vm); One issue still left in i915_gem_object_unbind is that it temporarily removes vmas from the obj->vma.list and adds back later as vma needs to be unbind outside the obj->vma.lock spinlock. This is an issue for other places where we iterate over the obj->vma.list. i915_debugfs_describe_obj is one such case (upcoming vm_bind will be another) that iterates over this list. What is the plan here? Do we need to take object lock while iterating over the list? But this just something I noticed and not related to this patch. This patch looks good to me. Reviewed-by: Niranjana Vishwanathapura >diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c >index 91538bc38110..6fd25b39748f 100644 >--- a/drivers/gpu/drm/i915/i915_vma.c >+++ b/drivers/gpu/drm/i915/i915_vma.c >@@ -122,7 +122,6 @@ vma_create(struct drm_i915_gem_object *obj, > if (vma == NULL) > return ERR_PTR(-ENOMEM); > >- kref_init(&vma->ref); > vma->ops = &vm->vma_ops; > vma->obj = obj; > vma->size = obj->base.size; >@@ -1628,15 +1627,6 @@ void i915_vma_reopen(struct i915_vma *vma) > __i915_vma_remove_closed(vma); > } > >-void i915_vma_release(struct kref *ref) >-{ >- struct i915_vma *vma = container_of(ref, typeof(*vma), ref); >- >- i915_active_fini(&vma->active); >- GEM_WARN_ON(vma->resource); >- i915_vma_free(vma); >-} >- > static void force_unbind(struct i915_vma *vma) > { > if (!drm_mm_node_allocated(&vma->node)) >@@ -1665,7 +1655,9 @@ static void release_references(struct i915_vma *vma, bool vm_ddestroy) > if (vm_ddestroy) > i915_vm_resv_put(vma->vm); > >- __i915_vma_put(vma); >+ i915_active_fini(&vma->active); >+ GEM_WARN_ON(vma->resource); >+ i915_vma_free(vma); > } > > /** >diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h >index 67ae7341c7e0..6034991d89fe 100644 >--- a/drivers/gpu/drm/i915/i915_vma.h >+++ b/drivers/gpu/drm/i915/i915_vma.h >@@ -222,20 +222,6 @@ void i915_vma_unlink_ctx(struct i915_vma *vma); > void i915_vma_close(struct i915_vma *vma); > void i915_vma_reopen(struct i915_vma *vma); > >-static inline struct i915_vma *__i915_vma_get(struct i915_vma *vma) >-{ >- if (kref_get_unless_zero(&vma->ref)) >- return vma; >- >- return NULL; >-} >- >-void i915_vma_release(struct kref *ref); >-static inline void __i915_vma_put(struct i915_vma *vma) >-{ >- kref_put(&vma->ref, i915_vma_release); >-} >- > void i915_vma_destroy_locked(struct i915_vma *vma); > void i915_vma_destroy(struct i915_vma *vma); > >diff --git a/drivers/gpu/drm/i915/i915_vma_types.h b/drivers/gpu/drm/i915/i915_vma_types.h >index eac36be184e5..be6e028c3b57 100644 >--- a/drivers/gpu/drm/i915/i915_vma_types.h >+++ b/drivers/gpu/drm/i915/i915_vma_types.h >@@ -211,7 +211,6 @@ struct i915_vma { > * handles (but same file) for execbuf, i.e. the number of aliases > * that exist in the ctx->handle_vmas LUT for this vma. > */ >- struct kref ref; > atomic_t open_count; > atomic_t flags; > /** >-- >2.34.1 > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9E75FC433EF for ; Wed, 2 Mar 2022 21:59:26 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id DDBB310E6D1; Wed, 2 Mar 2022 21:59:25 +0000 (UTC) Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by gabe.freedesktop.org (Postfix) with ESMTPS id E485A10E4ED; Wed, 2 Mar 2022 21:59:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1646258365; x=1677794365; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=yawzHkXCNEi4OGTe3ZX3h2CkuTgqHVGcefmuT5KID7w=; b=F+YLpV5jfW4i2IZDDncHmV68nIu58aCh7JyMi8ymvprGXKrEJHsjJoMe IXLCKJNMTDWdhfWxsUcPnWB59z63Ay7uBzY2SVjQngtRaDKSGN3EI3UqN rDXPPpoSroqF5Ly8DUWo+K7V1AD3F5R88I/97yV6ldnAn1kNrgN+fG5YZ mUm9Ve7ffOqh+yWtdhLM106cTS0kPVlNt9xHHwzqmP4/gR7dVbHk2AO4Q RaOphA9t4wVEktr8GDbZ7YhoF20vDpJzdRsYuGq4wX5IetU7CltSwdpU0 w2zkk0KANFgIrBDKGfr58RmWqJg7i0ynlDkNwOAR/hr1WX1eUe0mkjALO A==; X-IronPort-AV: E=McAfee;i="6200,9189,10274"; a="237024883" X-IronPort-AV: E=Sophos;i="5.90,150,1643702400"; d="scan'208";a="237024883" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Mar 2022 13:59:24 -0800 X-IronPort-AV: E=Sophos;i="5.90,150,1643702400"; d="scan'208";a="641858442" Received: from nvishwa1-desk.sc.intel.com (HELO nvishwa1-DESK) ([172.25.29.76]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Mar 2022 13:59:24 -0800 Date: Wed, 2 Mar 2022 14:01:41 -0800 From: Niranjana Vishwanathapura To: Thomas =?iso-8859-1?Q?Hellstr=F6m?= Message-ID: <20220302220139.GH25117@nvishwa1-DESK> References: <20220302102200.158637-1-thomas.hellstrom@linux.intel.com> <20220302102200.158637-3-thomas.hellstrom@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220302102200.158637-3-thomas.hellstrom@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Subject: Re: [Intel-gfx] [PATCH v2 2/3] drm/i915: Remove the vma refcount X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: intel-gfx@lists.freedesktop.org, matthew.auld@intel.com, dri-devel@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Wed, Mar 02, 2022 at 11:21:59AM +0100, Thomas Hellström wrote: >Now that i915_vma_parked() is taking the object lock on vma destruction, >and the only user of the vma refcount, i915_gem_object_unbind() >also takes the object lock, remove the vma refcount. > >Signed-off-by: Thomas Hellström >--- > drivers/gpu/drm/i915/i915_gem.c | 17 +++++++++++++---- > drivers/gpu/drm/i915/i915_vma.c | 14 +++----------- > drivers/gpu/drm/i915/i915_vma.h | 14 -------------- > drivers/gpu/drm/i915/i915_vma_types.h | 1 - > 4 files changed, 16 insertions(+), 30 deletions(-) > >diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c >index dd84ebabb50f..c26110abcc0b 100644 >--- a/drivers/gpu/drm/i915/i915_gem.c >+++ b/drivers/gpu/drm/i915/i915_gem.c >@@ -151,14 +151,25 @@ int i915_gem_object_unbind(struct drm_i915_gem_object *obj, > break; > } > >+ /* >+ * Requiring the vm destructor to take the object lock >+ * before destroying a vma would help us eliminate the >+ * i915_vm_tryget() here, AND thus also the barrier stuff >+ * at the end. That's an easy fix, but sleeping locks in >+ * a kthread should generally be avoided. >+ */ > ret = -EAGAIN; > if (!i915_vm_tryget(vma->vm)) > break; > >- /* Prevent vma being freed by i915_vma_parked as we unbind */ >- vma = __i915_vma_get(vma); > spin_unlock(&obj->vma.lock); > >+ /* >+ * Since i915_vma_parked() takes the object lock >+ * before vma destruction, it won't race us here, >+ * and destroy the vma from under us. >+ */ >+ > if (vma) { > bool vm_trylock = !!(flags & I915_GEM_OBJECT_UNBIND_VM_TRYLOCK); > ret = -EBUSY; >@@ -180,8 +191,6 @@ int i915_gem_object_unbind(struct drm_i915_gem_object *obj, > ret = i915_vma_unbind(vma); > } > } >- >- __i915_vma_put(vma); > } > > i915_vm_put(vma->vm); One issue still left in i915_gem_object_unbind is that it temporarily removes vmas from the obj->vma.list and adds back later as vma needs to be unbind outside the obj->vma.lock spinlock. This is an issue for other places where we iterate over the obj->vma.list. i915_debugfs_describe_obj is one such case (upcoming vm_bind will be another) that iterates over this list. What is the plan here? Do we need to take object lock while iterating over the list? But this just something I noticed and not related to this patch. This patch looks good to me. Reviewed-by: Niranjana Vishwanathapura >diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c >index 91538bc38110..6fd25b39748f 100644 >--- a/drivers/gpu/drm/i915/i915_vma.c >+++ b/drivers/gpu/drm/i915/i915_vma.c >@@ -122,7 +122,6 @@ vma_create(struct drm_i915_gem_object *obj, > if (vma == NULL) > return ERR_PTR(-ENOMEM); > >- kref_init(&vma->ref); > vma->ops = &vm->vma_ops; > vma->obj = obj; > vma->size = obj->base.size; >@@ -1628,15 +1627,6 @@ void i915_vma_reopen(struct i915_vma *vma) > __i915_vma_remove_closed(vma); > } > >-void i915_vma_release(struct kref *ref) >-{ >- struct i915_vma *vma = container_of(ref, typeof(*vma), ref); >- >- i915_active_fini(&vma->active); >- GEM_WARN_ON(vma->resource); >- i915_vma_free(vma); >-} >- > static void force_unbind(struct i915_vma *vma) > { > if (!drm_mm_node_allocated(&vma->node)) >@@ -1665,7 +1655,9 @@ static void release_references(struct i915_vma *vma, bool vm_ddestroy) > if (vm_ddestroy) > i915_vm_resv_put(vma->vm); > >- __i915_vma_put(vma); >+ i915_active_fini(&vma->active); >+ GEM_WARN_ON(vma->resource); >+ i915_vma_free(vma); > } > > /** >diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h >index 67ae7341c7e0..6034991d89fe 100644 >--- a/drivers/gpu/drm/i915/i915_vma.h >+++ b/drivers/gpu/drm/i915/i915_vma.h >@@ -222,20 +222,6 @@ void i915_vma_unlink_ctx(struct i915_vma *vma); > void i915_vma_close(struct i915_vma *vma); > void i915_vma_reopen(struct i915_vma *vma); > >-static inline struct i915_vma *__i915_vma_get(struct i915_vma *vma) >-{ >- if (kref_get_unless_zero(&vma->ref)) >- return vma; >- >- return NULL; >-} >- >-void i915_vma_release(struct kref *ref); >-static inline void __i915_vma_put(struct i915_vma *vma) >-{ >- kref_put(&vma->ref, i915_vma_release); >-} >- > void i915_vma_destroy_locked(struct i915_vma *vma); > void i915_vma_destroy(struct i915_vma *vma); > >diff --git a/drivers/gpu/drm/i915/i915_vma_types.h b/drivers/gpu/drm/i915/i915_vma_types.h >index eac36be184e5..be6e028c3b57 100644 >--- a/drivers/gpu/drm/i915/i915_vma_types.h >+++ b/drivers/gpu/drm/i915/i915_vma_types.h >@@ -211,7 +211,6 @@ struct i915_vma { > * handles (but same file) for execbuf, i.e. the number of aliases > * that exist in the ctx->handle_vmas LUT for this vma. > */ >- struct kref ref; > atomic_t open_count; > atomic_t flags; > /** >-- >2.34.1 >