atc_complete_all() had concurrency bugs, thus remove it: 1/ atc_complete_all() in its entirety was buggy, as when the atchan->queue list (the one that contains descriptors that are not yet issued to the hardware) contained descriptors, it fired just the first from the atchan->queue, but moved all the desc from atchan->queue to atchan->active_list and considered them all as fired. This could result in calling the completion of a descriptor that was not yet issued to the hardware. 2/ when in tasklet at atc_advance_work() time, atchan->active_list was queried without holding the lock of the chan. This can result in atchan->active_list concurrency problems between the tasklet and issue_pending().
Fixes: dc78baa2b90b ("dmaengine: at_hdmac: new driver for the Atmel AHB DMA Controller") Reported-by: Peter Rosin peda@axentia.se Signed-off-by: Tudor Ambarus tudor.ambarus@microchip.com Cc: stable@vger.kernel.org Link: https://lore.kernel.org/lkml/13c6c9a2-6db5-c3bf-349b-4c127ad3496a@axentia.se... --- drivers/dma/at_hdmac.c | 49 ++++-------------------------------------- 1 file changed, 4 insertions(+), 45 deletions(-)
diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c index deb4c6027436..f1e6fa6af6c2 100644 --- a/drivers/dma/at_hdmac.c +++ b/drivers/dma/at_hdmac.c @@ -485,42 +485,6 @@ atc_chain_complete(struct at_dma_chan *atchan, struct at_desc *desc) dma_run_dependencies(txd); }
-/** - * atc_complete_all - finish work for all transactions - * @atchan: channel to complete transactions for - * - * Eventually submit queued descriptors if any - * - * Assume channel is idle while calling this function - * Called with atchan->lock held and bh disabled - */ -static void atc_complete_all(struct at_dma_chan *atchan) -{ - struct at_desc *desc, *_desc; - LIST_HEAD(list); - unsigned long flags; - - dev_vdbg(chan2dev(&atchan->chan_common), "complete all\n"); - - spin_lock_irqsave(&atchan->lock, flags); - - /* - * Submit queued descriptors ASAP, i.e. before we go through - * the completed ones. - */ - if (!list_empty(&atchan->queue)) - atc_dostart(atchan, atc_first_queued(atchan)); - /* empty active_list now it is completed */ - list_splice_init(&atchan->active_list, &list); - /* empty queue list by moving descriptors (if any) to active_list */ - list_splice_init(&atchan->queue, &atchan->active_list); - - spin_unlock_irqrestore(&atchan->lock, flags); - - list_for_each_entry_safe(desc, _desc, &list, desc_node) - atc_chain_complete(atchan, desc); -} - /** * atc_advance_work - at the end of a transaction, move forward * @atchan: channel where the transaction ended @@ -528,25 +492,20 @@ static void atc_complete_all(struct at_dma_chan *atchan) static void atc_advance_work(struct at_dma_chan *atchan) { unsigned long flags; - int ret;
dev_vdbg(chan2dev(&atchan->chan_common), "advance_work\n");
spin_lock_irqsave(&atchan->lock, flags); - ret = atc_chan_is_enabled(atchan); + if (atc_chan_is_enabled(atchan) || list_empty(&atchan->active_list)) + return spin_unlock_irqrestore(&atchan->lock, flags); spin_unlock_irqrestore(&atchan->lock, flags); - if (ret) - return; - - if (list_empty(&atchan->active_list) || - list_is_singular(&atchan->active_list)) - return atc_complete_all(atchan);
atc_chain_complete(atchan, atc_first_active(atchan));
/* advance work */ spin_lock_irqsave(&atchan->lock, flags); - atc_dostart(atchan, atc_first_active(atchan)); + if (!list_empty(&atchan->active_list)) + atc_dostart(atchan, atc_first_active(atchan)); spin_unlock_irqrestore(&atchan->lock, flags); }