ioat: close potential BUG_ON race in the descriptor cleanup path
Dan Williams [Thu, 4 Mar 2010 04:21:10 +0000 (21:21 -0700)]
Since ioat_cleanup_preamble() and the update of the last completed
descriptor are not synchronized there is a chance that two cleanup threads
can see descriptors to clean.  If the first cleans up all pending
descriptors then the second will trigger the BUG_ON.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/dma/ioat/dma_v2.c
drivers/dma/ioat/dma_v3.c

index c6e4531..01ed1cf 100644 (file)
@@ -158,7 +158,7 @@ static void __cleanup(struct ioat2_dma_chan *ioat, unsigned long phys_complete)
                        seen_current = true;
        }
        ioat->tail += i;
-       BUG_ON(!seen_current); /* no active descs have written a completion? */
+       BUG_ON(active && !seen_current); /* no active descs have written a completion? */
 
        chan->last_completion = phys_complete;
        if (ioat->head == ioat->tail) {
index bff48e8..39520f2 100644 (file)
@@ -293,7 +293,7 @@ static void __cleanup(struct ioat2_dma_chan *ioat, unsigned long phys_complete)
                }
        }
        ioat->tail += i;
-       BUG_ON(!seen_current); /* no active descs have written a completion? */
+       BUG_ON(active && !seen_current); /* no active descs have written a completion? */
        chan->last_completion = phys_complete;
        if (ioat->head == ioat->tail) {
                dev_dbg(to_dev(chan), "%s: cancel completion timeout\n",