On 09/25/2017 04:38 PM, Stefan Roese wrote: > Hi Sylvain, > > On 18.09.2017 13:08, Sylvain Lesne wrote: >> Since this lock is acquired in both process and IRQ context, failing to >> to disable IRQs when trying to acquire the lock in process context can >> lead to deadlocks. >> >> Signed-off-by: Sylvain Lesne <lesne@xxxxxxxxxxx> >> --- >> I'm not sure that this is the "smartest" fix, but I think something >> should be done to fix the spinlock usage in this driver (lockdep >> agrees!). > > I'm a bit unsure here as well, as introducing the irqsave spinlocks > here will be a bit costly time-wise. > > Perhaps its better to move the addition of new descriptors in the IDLE > state from the ISR back the IRQ tasklet, as I've initially proposed in > v2 of this patch: > > https://patchwork.kernel.org/patch/9805967/ > > This way, the lock will not be used from IRQ context any more and > the "normal" spinlock calls should be enough. > > What do you think? Thanks for the feedback! I agree that simplifying the locks is probably the best idea. Since Vinod suggested that you move this in the IRQ for performance reasons, moving it back to the tasklet could cause a performance hit, but this is probably better than adding irqsave everywhere. Thanks, Sylvain > > Thanks, > Stefan > >> --- >> drivers/dma/altera-msgdma.c | 35 +++++++++++++++++++++-------------- >> 1 file changed, 21 insertions(+), 14 deletions(-) >> >> diff --git a/drivers/dma/altera-msgdma.c b/drivers/dma/altera-msgdma.c >> index 35cbf2365f68..339186f25a2a 100644 >> --- a/drivers/dma/altera-msgdma.c >> +++ b/drivers/dma/altera-msgdma.c >> @@ -212,11 +212,12 @@ struct msgdma_device { >> static struct msgdma_sw_desc *msgdma_get_descriptor(struct >> msgdma_device *mdev) >> { >> struct msgdma_sw_desc *desc; >> + unsigned long flags; >> - spin_lock_bh(&mdev->lock); >> + spin_lock_irqsave(&mdev->lock, flags); >> desc = list_first_entry(&mdev->free_list, struct msgdma_sw_desc, >> node); >> list_del(&desc->node); >> - spin_unlock_bh(&mdev->lock); >> + spin_unlock_irqrestore(&mdev->lock, flags); >> INIT_LIST_HEAD(&desc->tx_list); >> @@ -306,13 +307,14 @@ static dma_cookie_t msgdma_tx_submit(struct >> dma_async_tx_descriptor *tx) >> struct msgdma_device *mdev = to_mdev(tx->chan); >> struct msgdma_sw_desc *new; >> dma_cookie_t cookie; >> + unsigned long flags; >> new = tx_to_desc(tx); >> - spin_lock_bh(&mdev->lock); >> + spin_lock_irqsave(&mdev->lock, flags); >> cookie = dma_cookie_assign(tx); >> list_add_tail(&new->node, &mdev->pending_list); >> - spin_unlock_bh(&mdev->lock); >> + spin_unlock_irqrestore(&mdev->lock, flags); >> return cookie; >> } >> @@ -336,17 +338,18 @@ msgdma_prep_memcpy(struct dma_chan *dchan, >> dma_addr_t dma_dst, >> struct msgdma_extended_desc *desc; >> size_t copy; >> u32 desc_cnt; >> + unsigned long irqflags; >> desc_cnt = DIV_ROUND_UP(len, MSGDMA_MAX_TRANS_LEN); >> - spin_lock_bh(&mdev->lock); >> + spin_lock_irqsave(&mdev->lock, irqflags); >> if (desc_cnt > mdev->desc_free_cnt) { >> spin_unlock_bh(&mdev->lock); >> dev_dbg(mdev->dev, "mdev %p descs are not available\n", mdev); >> return NULL; >> } >> mdev->desc_free_cnt -= desc_cnt; >> - spin_unlock_bh(&mdev->lock); >> + spin_unlock_irqrestore(&mdev->lock, irqflags); >> do { >> /* Allocate and populate the descriptor */ >> @@ -397,18 +400,19 @@ msgdma_prep_slave_sg(struct dma_chan *dchan, >> struct scatterlist *sgl, >> u32 desc_cnt = 0, i; >> struct scatterlist *sg; >> u32 stride; >> + unsigned long irqflags; >> for_each_sg(sgl, sg, sg_len, i) >> desc_cnt += DIV_ROUND_UP(sg_dma_len(sg), MSGDMA_MAX_TRANS_LEN); >> - spin_lock_bh(&mdev->lock); >> + spin_lock_irqsave(&mdev->lock, irqflags); >> if (desc_cnt > mdev->desc_free_cnt) { >> spin_unlock_bh(&mdev->lock); >> dev_dbg(mdev->dev, "mdev %p descs are not available\n", mdev); >> return NULL; >> } >> mdev->desc_free_cnt -= desc_cnt; >> - spin_unlock_bh(&mdev->lock); >> + spin_unlock_irqrestore(&mdev->lock, irqflags); >> avail = sg_dma_len(sgl); >> @@ -566,10 +570,11 @@ static void msgdma_start_transfer(struct >> msgdma_device *mdev) >> static void msgdma_issue_pending(struct dma_chan *chan) >> { >> struct msgdma_device *mdev = to_mdev(chan); >> + unsigned long flags; >> - spin_lock_bh(&mdev->lock); >> + spin_lock_irqsave(&mdev->lock, flags); >> msgdma_start_transfer(mdev); >> - spin_unlock_bh(&mdev->lock); >> + spin_unlock_irqrestore(&mdev->lock, flags); >> } >> /** >> @@ -634,10 +639,11 @@ static void msgdma_free_descriptors(struct >> msgdma_device *mdev) >> static void msgdma_free_chan_resources(struct dma_chan *dchan) >> { >> struct msgdma_device *mdev = to_mdev(dchan); >> + unsigned long flags; >> - spin_lock_bh(&mdev->lock); >> + spin_lock_irqsave(&mdev->lock, flags); >> msgdma_free_descriptors(mdev); >> - spin_unlock_bh(&mdev->lock); >> + spin_unlock_irqrestore(&mdev->lock, flags); >> kfree(mdev->sw_desq); >> } >> @@ -682,8 +688,9 @@ static void msgdma_tasklet(unsigned long data) >> u32 count; >> u32 __maybe_unused size; >> u32 __maybe_unused status; >> + unsigned long flags; >> - spin_lock(&mdev->lock); >> + spin_lock_irqsave(&mdev->lock, flags); >> /* Read number of responses that are available */ >> count = ioread32(mdev->csr + MSGDMA_CSR_RESP_FILL_LEVEL); >> @@ -704,7 +711,7 @@ static void msgdma_tasklet(unsigned long data) >> msgdma_chan_desc_cleanup(mdev); >> } >> - spin_unlock(&mdev->lock); >> + spin_unlock_irqrestore(&mdev->lock, flags); >> } >> /** >> > > Viele Grüße, > Stefan > -- ALSE - Sylvain Lesne 8 Passage Barrault 75013 PARIS - FRANCE Tel (standard) : +33 1 84 16 32 32 Mail : lesne@xxxxxxxxxxx Web : http://www.alse-fr.com -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
