1c7f072d94
Even with the introduced vchan_synchronize() we can face race when terminating a cyclic transfer. If the terminate_all is called after the interrupt handler called vchan_cyclic_callback(), but before the vchan_complete tasklet is called: vc->cyclic is set to the cyclic descriptor, but the descriptor itself was freed up in the driver's terminate_all() callback. When the vhan_complete() is executed it will try to fetch the vc->cyclic vdesc, but the pointer is pointing now to uninitialized memory leading to (hard to reproduce) kernel crash. In order to fix this, drivers should: - call vchan_terminate_vdesc() from their terminate_all callback instead calling their free_desc function to free up the descriptor. - implement device_synchronize callback and call vchan_synchronize(). This way we can make sure that the descriptor is only going to be freed up after the vchan_callback was executed in a safe manner. Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Vinod Koul <vinod.koul@intel.com>
221 lines
5.8 KiB
C
221 lines
5.8 KiB
C
/*
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* Virtual DMA channel support for DMAengine
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*
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* Copyright (C) 2012 Russell King
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef VIRT_DMA_H
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#define VIRT_DMA_H
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#include <linux/dmaengine.h>
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#include <linux/interrupt.h>
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#include "dmaengine.h"
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struct virt_dma_desc {
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struct dma_async_tx_descriptor tx;
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/* protected by vc.lock */
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struct list_head node;
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};
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struct virt_dma_chan {
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struct dma_chan chan;
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struct tasklet_struct task;
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void (*desc_free)(struct virt_dma_desc *);
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spinlock_t lock;
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/* protected by vc.lock */
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struct list_head desc_allocated;
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struct list_head desc_submitted;
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struct list_head desc_issued;
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struct list_head desc_completed;
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struct virt_dma_desc *cyclic;
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struct virt_dma_desc *vd_terminated;
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};
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static inline struct virt_dma_chan *to_virt_chan(struct dma_chan *chan)
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{
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return container_of(chan, struct virt_dma_chan, chan);
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}
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void vchan_dma_desc_free_list(struct virt_dma_chan *vc, struct list_head *head);
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void vchan_init(struct virt_dma_chan *vc, struct dma_device *dmadev);
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struct virt_dma_desc *vchan_find_desc(struct virt_dma_chan *, dma_cookie_t);
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extern dma_cookie_t vchan_tx_submit(struct dma_async_tx_descriptor *);
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extern int vchan_tx_desc_free(struct dma_async_tx_descriptor *);
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/**
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* vchan_tx_prep - prepare a descriptor
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* @vc: virtual channel allocating this descriptor
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* @vd: virtual descriptor to prepare
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* @tx_flags: flags argument passed in to prepare function
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*/
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static inline struct dma_async_tx_descriptor *vchan_tx_prep(struct virt_dma_chan *vc,
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struct virt_dma_desc *vd, unsigned long tx_flags)
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{
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unsigned long flags;
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dma_async_tx_descriptor_init(&vd->tx, &vc->chan);
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vd->tx.flags = tx_flags;
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vd->tx.tx_submit = vchan_tx_submit;
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vd->tx.desc_free = vchan_tx_desc_free;
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spin_lock_irqsave(&vc->lock, flags);
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list_add_tail(&vd->node, &vc->desc_allocated);
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spin_unlock_irqrestore(&vc->lock, flags);
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return &vd->tx;
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}
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/**
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* vchan_issue_pending - move submitted descriptors to issued list
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* @vc: virtual channel to update
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*
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* vc.lock must be held by caller
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*/
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static inline bool vchan_issue_pending(struct virt_dma_chan *vc)
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{
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list_splice_tail_init(&vc->desc_submitted, &vc->desc_issued);
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return !list_empty(&vc->desc_issued);
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}
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/**
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* vchan_cookie_complete - report completion of a descriptor
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* @vd: virtual descriptor to update
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*
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* vc.lock must be held by caller
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*/
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static inline void vchan_cookie_complete(struct virt_dma_desc *vd)
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{
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struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
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dma_cookie_t cookie;
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cookie = vd->tx.cookie;
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dma_cookie_complete(&vd->tx);
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dev_vdbg(vc->chan.device->dev, "txd %p[%x]: marked complete\n",
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vd, cookie);
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list_add_tail(&vd->node, &vc->desc_completed);
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tasklet_schedule(&vc->task);
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}
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/**
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* vchan_vdesc_fini - Free or reuse a descriptor
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* @vd: virtual descriptor to free/reuse
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*/
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static inline void vchan_vdesc_fini(struct virt_dma_desc *vd)
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{
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struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
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if (dmaengine_desc_test_reuse(&vd->tx))
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list_add(&vd->node, &vc->desc_allocated);
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else
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vc->desc_free(vd);
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}
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/**
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* vchan_cyclic_callback - report the completion of a period
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* @vd: virtual descriptor
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*/
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static inline void vchan_cyclic_callback(struct virt_dma_desc *vd)
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{
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struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
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vc->cyclic = vd;
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tasklet_schedule(&vc->task);
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}
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/**
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* vchan_terminate_vdesc - Disable pending cyclic callback
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* @vd: virtual descriptor to be terminated
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*
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* vc.lock must be held by caller
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*/
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static inline void vchan_terminate_vdesc(struct virt_dma_desc *vd)
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{
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struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
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/* free up stuck descriptor */
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if (vc->vd_terminated)
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vchan_vdesc_fini(vc->vd_terminated);
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vc->vd_terminated = vd;
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if (vc->cyclic == vd)
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vc->cyclic = NULL;
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}
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/**
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* vchan_next_desc - peek at the next descriptor to be processed
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* @vc: virtual channel to obtain descriptor from
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*
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* vc.lock must be held by caller
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*/
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static inline struct virt_dma_desc *vchan_next_desc(struct virt_dma_chan *vc)
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{
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return list_first_entry_or_null(&vc->desc_issued,
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struct virt_dma_desc, node);
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}
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/**
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* vchan_get_all_descriptors - obtain all submitted and issued descriptors
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* @vc: virtual channel to get descriptors from
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* @head: list of descriptors found
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*
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* vc.lock must be held by caller
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*
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* Removes all submitted and issued descriptors from internal lists, and
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* provides a list of all descriptors found
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*/
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static inline void vchan_get_all_descriptors(struct virt_dma_chan *vc,
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struct list_head *head)
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{
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list_splice_tail_init(&vc->desc_allocated, head);
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list_splice_tail_init(&vc->desc_submitted, head);
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list_splice_tail_init(&vc->desc_issued, head);
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list_splice_tail_init(&vc->desc_completed, head);
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}
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static inline void vchan_free_chan_resources(struct virt_dma_chan *vc)
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{
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struct virt_dma_desc *vd;
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unsigned long flags;
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LIST_HEAD(head);
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spin_lock_irqsave(&vc->lock, flags);
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vchan_get_all_descriptors(vc, &head);
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list_for_each_entry(vd, &head, node)
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dmaengine_desc_clear_reuse(&vd->tx);
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spin_unlock_irqrestore(&vc->lock, flags);
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vchan_dma_desc_free_list(vc, &head);
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}
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/**
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* vchan_synchronize() - synchronize callback execution to the current context
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* @vc: virtual channel to synchronize
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*
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* Makes sure that all scheduled or active callbacks have finished running. For
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* proper operation the caller has to ensure that no new callbacks are scheduled
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* after the invocation of this function started.
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* Free up the terminated cyclic descriptor to prevent memory leakage.
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*/
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static inline void vchan_synchronize(struct virt_dma_chan *vc)
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{
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unsigned long flags;
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tasklet_kill(&vc->task);
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spin_lock_irqsave(&vc->lock, flags);
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if (vc->vd_terminated) {
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vchan_vdesc_fini(vc->vd_terminated);
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vc->vd_terminated = NULL;
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}
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spin_unlock_irqrestore(&vc->lock, flags);
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}
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#endif
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