dmaengine: at_hdmac: fix race condition in atc_advance_work()

The BUG_ON() directive is triggered probably due to a latency
modification following inclusion of commit c10d73671ad3 ("softirq:
reduce latencies").  This condition has not been met before 3.9-rc1 and
doesn't trigger without this patch.

We now make sure that DMA channel is idle before calling
atc_complete_all() which makes the BUG_ON() "protection" useless.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 5 deletions

diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
index 6e13f262139a..88cfc61329d2 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -310,8 +310,6 @@ static void atc_complete_all(struct at_dma_chan *atchan)
 
         dev_vdbg(chan2dev(&atchan->chan_common), "complete all\n");
 
-        BUG_ON(atc_chan_is_enabled(atchan));
-
         /*
          * Submit queued descriptors ASAP, i.e. before we go through
          * the completed ones.
@@ -368,6 +366,9 @@ static void atc_advance_work(struct at_dma_chan *atchan)
 {
         dev_vdbg(chan2dev(&atchan->chan_common), "advance_work\n");
 
+        if (atc_chan_is_enabled(atchan))
+                return;
+
         if (list_empty(&atchan->active_list) ||
             list_is_singular(&atchan->active_list)) {
                 atc_complete_all(atchan);
@@ -1078,9 +1079,7 @@ static void atc_issue_pending(struct dma_chan *chan)
                 return;
 
         spin_lock_irqsave(&atchan->lock, flags);
-        if (!atc_chan_is_enabled(atchan)) {
-                atc_advance_work(atchan);
-        }
+        atc_advance_work(atchan);
         spin_unlock_irqrestore(&atchan->lock, flags);
 }