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![Rob Clark](/assets/img/avatar_default.png)
Signed-off-by: Rob Clark <robdclark@gmail.com> [danvet: Mark up as function for proper cross-linking.] Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/1471640134-30888-1-git-send-email-robdclark@gmail.com
545 lines
13 KiB
C
545 lines
13 KiB
C
/*
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* Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
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*
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* Based on bo.c which bears the following copyright notice,
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* but is dual licensed:
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*
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* Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
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* All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sub license, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice (including the
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* next paragraph) shall be included in all copies or substantial portions
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* of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
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* THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
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* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
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* USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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**************************************************************************/
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/*
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* Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
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*/
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#include <linux/reservation.h>
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#include <linux/export.h>
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/**
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* DOC: Reservation Object Overview
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*
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* The reservation object provides a mechanism to manage shared and
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* exclusive fences associated with a buffer. A reservation object
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* can have attached one exclusive fence (normally associated with
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* write operations) or N shared fences (read operations). The RCU
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* mechanism is used to protect read access to fences from locked
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* write-side updates.
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*/
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DEFINE_WW_CLASS(reservation_ww_class);
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EXPORT_SYMBOL(reservation_ww_class);
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struct lock_class_key reservation_seqcount_class;
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EXPORT_SYMBOL(reservation_seqcount_class);
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const char reservation_seqcount_string[] = "reservation_seqcount";
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EXPORT_SYMBOL(reservation_seqcount_string);
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/**
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* reservation_object_reserve_shared - Reserve space to add a shared
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* fence to a reservation_object.
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* @obj: reservation object
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*
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* Should be called before reservation_object_add_shared_fence(). Must
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* be called with obj->lock held.
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*
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* RETURNS
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* Zero for success, or -errno
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*/
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int reservation_object_reserve_shared(struct reservation_object *obj)
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{
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struct reservation_object_list *fobj, *old;
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u32 max;
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old = reservation_object_get_list(obj);
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if (old && old->shared_max) {
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if (old->shared_count < old->shared_max) {
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/* perform an in-place update */
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kfree(obj->staged);
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obj->staged = NULL;
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return 0;
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} else
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max = old->shared_max * 2;
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} else
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max = 4;
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/*
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* resize obj->staged or allocate if it doesn't exist,
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* noop if already correct size
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*/
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fobj = krealloc(obj->staged, offsetof(typeof(*fobj), shared[max]),
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GFP_KERNEL);
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if (!fobj)
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return -ENOMEM;
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obj->staged = fobj;
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fobj->shared_max = max;
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return 0;
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}
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EXPORT_SYMBOL(reservation_object_reserve_shared);
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static void
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reservation_object_add_shared_inplace(struct reservation_object *obj,
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struct reservation_object_list *fobj,
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struct fence *fence)
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{
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u32 i;
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fence_get(fence);
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preempt_disable();
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write_seqcount_begin(&obj->seq);
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for (i = 0; i < fobj->shared_count; ++i) {
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struct fence *old_fence;
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old_fence = rcu_dereference_protected(fobj->shared[i],
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reservation_object_held(obj));
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if (old_fence->context == fence->context) {
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/* memory barrier is added by write_seqcount_begin */
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RCU_INIT_POINTER(fobj->shared[i], fence);
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write_seqcount_end(&obj->seq);
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preempt_enable();
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fence_put(old_fence);
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return;
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}
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}
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/*
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* memory barrier is added by write_seqcount_begin,
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* fobj->shared_count is protected by this lock too
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*/
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RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
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fobj->shared_count++;
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write_seqcount_end(&obj->seq);
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preempt_enable();
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}
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static void
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reservation_object_add_shared_replace(struct reservation_object *obj,
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struct reservation_object_list *old,
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struct reservation_object_list *fobj,
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struct fence *fence)
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{
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unsigned i;
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struct fence *old_fence = NULL;
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fence_get(fence);
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if (!old) {
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RCU_INIT_POINTER(fobj->shared[0], fence);
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fobj->shared_count = 1;
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goto done;
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}
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/*
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* no need to bump fence refcounts, rcu_read access
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* requires the use of kref_get_unless_zero, and the
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* references from the old struct are carried over to
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* the new.
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*/
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fobj->shared_count = old->shared_count;
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for (i = 0; i < old->shared_count; ++i) {
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struct fence *check;
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check = rcu_dereference_protected(old->shared[i],
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reservation_object_held(obj));
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if (!old_fence && check->context == fence->context) {
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old_fence = check;
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RCU_INIT_POINTER(fobj->shared[i], fence);
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} else
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RCU_INIT_POINTER(fobj->shared[i], check);
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}
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if (!old_fence) {
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RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
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fobj->shared_count++;
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}
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done:
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preempt_disable();
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write_seqcount_begin(&obj->seq);
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/*
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* RCU_INIT_POINTER can be used here,
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* seqcount provides the necessary barriers
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*/
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RCU_INIT_POINTER(obj->fence, fobj);
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write_seqcount_end(&obj->seq);
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preempt_enable();
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if (old)
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kfree_rcu(old, rcu);
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if (old_fence)
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fence_put(old_fence);
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}
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/**
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* reservation_object_add_shared_fence - Add a fence to a shared slot
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* @obj: the reservation object
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* @fence: the shared fence to add
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*
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* Add a fence to a shared slot, obj->lock must be held, and
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* reservation_object_reserve_shared() has been called.
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*/
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void reservation_object_add_shared_fence(struct reservation_object *obj,
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struct fence *fence)
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{
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struct reservation_object_list *old, *fobj = obj->staged;
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old = reservation_object_get_list(obj);
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obj->staged = NULL;
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if (!fobj) {
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BUG_ON(old->shared_count >= old->shared_max);
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reservation_object_add_shared_inplace(obj, old, fence);
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} else
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reservation_object_add_shared_replace(obj, old, fobj, fence);
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}
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EXPORT_SYMBOL(reservation_object_add_shared_fence);
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/**
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* reservation_object_add_excl_fence - Add an exclusive fence.
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* @obj: the reservation object
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* @fence: the shared fence to add
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*
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* Add a fence to the exclusive slot. The obj->lock must be held.
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*/
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void reservation_object_add_excl_fence(struct reservation_object *obj,
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struct fence *fence)
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{
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struct fence *old_fence = reservation_object_get_excl(obj);
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struct reservation_object_list *old;
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u32 i = 0;
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old = reservation_object_get_list(obj);
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if (old)
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i = old->shared_count;
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if (fence)
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fence_get(fence);
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preempt_disable();
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write_seqcount_begin(&obj->seq);
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/* write_seqcount_begin provides the necessary memory barrier */
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RCU_INIT_POINTER(obj->fence_excl, fence);
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if (old)
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old->shared_count = 0;
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write_seqcount_end(&obj->seq);
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preempt_enable();
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/* inplace update, no shared fences */
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while (i--)
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fence_put(rcu_dereference_protected(old->shared[i],
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reservation_object_held(obj)));
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if (old_fence)
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fence_put(old_fence);
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}
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EXPORT_SYMBOL(reservation_object_add_excl_fence);
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/**
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* reservation_object_get_fences_rcu - Get an object's shared and exclusive
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* fences without update side lock held
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* @obj: the reservation object
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* @pfence_excl: the returned exclusive fence (or NULL)
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* @pshared_count: the number of shared fences returned
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* @pshared: the array of shared fence ptrs returned (array is krealloc'd to
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* the required size, and must be freed by caller)
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*
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* RETURNS
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* Zero or -errno
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*/
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int reservation_object_get_fences_rcu(struct reservation_object *obj,
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struct fence **pfence_excl,
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unsigned *pshared_count,
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struct fence ***pshared)
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{
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unsigned shared_count = 0;
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unsigned retry = 1;
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struct fence **shared = NULL, *fence_excl = NULL;
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int ret = 0;
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while (retry) {
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struct reservation_object_list *fobj;
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unsigned seq;
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seq = read_seqcount_begin(&obj->seq);
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rcu_read_lock();
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fobj = rcu_dereference(obj->fence);
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if (fobj) {
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struct fence **nshared;
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size_t sz = sizeof(*shared) * fobj->shared_max;
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nshared = krealloc(shared, sz,
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GFP_NOWAIT | __GFP_NOWARN);
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if (!nshared) {
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rcu_read_unlock();
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nshared = krealloc(shared, sz, GFP_KERNEL);
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if (nshared) {
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shared = nshared;
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continue;
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}
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ret = -ENOMEM;
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shared_count = 0;
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break;
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}
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shared = nshared;
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memcpy(shared, fobj->shared, sz);
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shared_count = fobj->shared_count;
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} else
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shared_count = 0;
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fence_excl = rcu_dereference(obj->fence_excl);
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retry = read_seqcount_retry(&obj->seq, seq);
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if (retry)
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goto unlock;
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if (!fence_excl || fence_get_rcu(fence_excl)) {
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unsigned i;
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for (i = 0; i < shared_count; ++i) {
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if (fence_get_rcu(shared[i]))
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continue;
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/* uh oh, refcount failed, abort and retry */
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while (i--)
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fence_put(shared[i]);
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if (fence_excl) {
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fence_put(fence_excl);
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fence_excl = NULL;
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}
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retry = 1;
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break;
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}
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} else
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retry = 1;
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unlock:
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rcu_read_unlock();
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}
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*pshared_count = shared_count;
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if (shared_count)
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*pshared = shared;
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else {
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*pshared = NULL;
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kfree(shared);
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}
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*pfence_excl = fence_excl;
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return ret;
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}
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EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
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/**
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* reservation_object_wait_timeout_rcu - Wait on reservation's objects
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* shared and/or exclusive fences.
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* @obj: the reservation object
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* @wait_all: if true, wait on all fences, else wait on just exclusive fence
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* @intr: if true, do interruptible wait
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* @timeout: timeout value in jiffies or zero to return immediately
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*
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* RETURNS
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* Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or
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* greater than zer on success.
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*/
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long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
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bool wait_all, bool intr,
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unsigned long timeout)
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{
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struct fence *fence;
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unsigned seq, shared_count, i = 0;
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long ret = timeout;
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if (!timeout)
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return reservation_object_test_signaled_rcu(obj, wait_all);
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retry:
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fence = NULL;
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shared_count = 0;
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seq = read_seqcount_begin(&obj->seq);
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rcu_read_lock();
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if (wait_all) {
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struct reservation_object_list *fobj =
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rcu_dereference(obj->fence);
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if (fobj)
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shared_count = fobj->shared_count;
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if (read_seqcount_retry(&obj->seq, seq))
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goto unlock_retry;
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for (i = 0; i < shared_count; ++i) {
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struct fence *lfence = rcu_dereference(fobj->shared[i]);
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if (test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags))
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continue;
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if (!fence_get_rcu(lfence))
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goto unlock_retry;
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if (fence_is_signaled(lfence)) {
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fence_put(lfence);
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continue;
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}
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fence = lfence;
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break;
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}
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}
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if (!shared_count) {
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struct fence *fence_excl = rcu_dereference(obj->fence_excl);
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if (read_seqcount_retry(&obj->seq, seq))
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goto unlock_retry;
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if (fence_excl &&
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!test_bit(FENCE_FLAG_SIGNALED_BIT, &fence_excl->flags)) {
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if (!fence_get_rcu(fence_excl))
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goto unlock_retry;
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if (fence_is_signaled(fence_excl))
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fence_put(fence_excl);
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else
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fence = fence_excl;
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}
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}
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rcu_read_unlock();
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if (fence) {
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ret = fence_wait_timeout(fence, intr, ret);
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fence_put(fence);
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if (ret > 0 && wait_all && (i + 1 < shared_count))
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goto retry;
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}
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return ret;
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unlock_retry:
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rcu_read_unlock();
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goto retry;
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}
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EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
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static inline int
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reservation_object_test_signaled_single(struct fence *passed_fence)
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{
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struct fence *fence, *lfence = passed_fence;
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int ret = 1;
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if (!test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
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fence = fence_get_rcu(lfence);
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if (!fence)
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return -1;
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ret = !!fence_is_signaled(fence);
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fence_put(fence);
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}
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return ret;
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}
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/**
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* reservation_object_test_signaled_rcu - Test if a reservation object's
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* fences have been signaled.
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* @obj: the reservation object
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* @test_all: if true, test all fences, otherwise only test the exclusive
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* fence
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*
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* RETURNS
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* true if all fences signaled, else false
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*/
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bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
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bool test_all)
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{
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unsigned seq, shared_count;
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int ret = true;
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retry:
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shared_count = 0;
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seq = read_seqcount_begin(&obj->seq);
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rcu_read_lock();
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if (test_all) {
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unsigned i;
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struct reservation_object_list *fobj =
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rcu_dereference(obj->fence);
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if (fobj)
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shared_count = fobj->shared_count;
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if (read_seqcount_retry(&obj->seq, seq))
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goto unlock_retry;
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for (i = 0; i < shared_count; ++i) {
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struct fence *fence = rcu_dereference(fobj->shared[i]);
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ret = reservation_object_test_signaled_single(fence);
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if (ret < 0)
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goto unlock_retry;
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else if (!ret)
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break;
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}
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/*
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* There could be a read_seqcount_retry here, but nothing cares
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* about whether it's the old or newer fence pointers that are
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* signaled. That race could still have happened after checking
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* read_seqcount_retry. If you care, use ww_mutex_lock.
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*/
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}
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if (!shared_count) {
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struct fence *fence_excl = rcu_dereference(obj->fence_excl);
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if (read_seqcount_retry(&obj->seq, seq))
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goto unlock_retry;
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if (fence_excl) {
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ret = reservation_object_test_signaled_single(
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fence_excl);
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if (ret < 0)
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goto unlock_retry;
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}
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}
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rcu_read_unlock();
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return ret;
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unlock_retry:
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|
rcu_read_unlock();
|
|
goto retry;
|
|
}
|
|
EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);
|