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author | Peter Ujfalusi <peter.ujfalusi@ti.com> | 2017-11-14 16:32:04 +0200 |
---|---|---|
committer | Vinod Koul <vinod.koul@intel.com> | 2017-12-04 22:33:51 +0530 |
commit | 1c7f072d94e8b697fd9b70cdb268622a18faf522 (patch) | |
tree | 706d68a16f1c1b17b99fde45d830b730e33e4932 /drivers/dma | |
parent | 6af149d2b1422e0e873d8558274713e6f63142c2 (diff) | |
download | op-kernel-dev-1c7f072d94e8b697fd9b70cdb268622a18faf522.zip op-kernel-dev-1c7f072d94e8b697fd9b70cdb268622a18faf522.tar.gz |
dmaengine: virt-dma: Support for race free transfer termination
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>
Diffstat (limited to 'drivers/dma')
-rw-r--r-- | drivers/dma/virt-dma.h | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/drivers/dma/virt-dma.h b/drivers/dma/virt-dma.h index 2edb055..b09b75a 100644 --- a/drivers/dma/virt-dma.h +++ b/drivers/dma/virt-dma.h @@ -35,6 +35,7 @@ struct virt_dma_chan { struct list_head desc_completed; struct virt_dma_desc *cyclic; + struct virt_dma_desc *vd_terminated; }; static inline struct virt_dma_chan *to_virt_chan(struct dma_chan *chan) @@ -130,6 +131,25 @@ static inline void vchan_cyclic_callback(struct virt_dma_desc *vd) } /** + * vchan_terminate_vdesc - Disable pending cyclic callback + * @vd: virtual descriptor to be terminated + * + * vc.lock must be held by caller + */ +static inline void vchan_terminate_vdesc(struct virt_dma_desc *vd) +{ + struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan); + + /* free up stuck descriptor */ + if (vc->vd_terminated) + vchan_vdesc_fini(vc->vd_terminated); + + vc->vd_terminated = vd; + if (vc->cyclic == vd) + vc->cyclic = NULL; +} + +/** * vchan_next_desc - peek at the next descriptor to be processed * @vc: virtual channel to obtain descriptor from * @@ -182,10 +202,20 @@ static inline void vchan_free_chan_resources(struct virt_dma_chan *vc) * Makes sure that all scheduled or active callbacks have finished running. For * proper operation the caller has to ensure that no new callbacks are scheduled * after the invocation of this function started. + * Free up the terminated cyclic descriptor to prevent memory leakage. */ static inline void vchan_synchronize(struct virt_dma_chan *vc) { + unsigned long flags; + tasklet_kill(&vc->task); + + spin_lock_irqsave(&vc->lock, flags); + if (vc->vd_terminated) { + vchan_vdesc_fini(vc->vd_terminated); + vc->vd_terminated = NULL; + } + spin_unlock_irqrestore(&vc->lock, flags); } #endif |