On Thu, Feb 13, 2014 at 4:49 PM, Sander Eikelenboom <[email protected]> wrote: > > Thursday, February 13, 2014, 9:14:47 PM, you wrote: > >> On Tue, 2014-02-11 at 20:17 -0800, Eric Dumazet wrote: >>> On Tue, 2014-02-11 at 18:07 -0800, Dan Williams wrote: >>> >>> > The overlap granularity is too large. Multiple dma_map_single >>> > mappings are allowed to a given page as long as they don't collide on >>> > the same cache line. >>> > >>> >>> I am not sure why you try number of mappings of a page. >>> >>> Try launching 100 concurrent netperf -t TCP_SENFILE >>> >>> Same page might be mapped more than 100 times, more than 10000 times in >>> some cases. > >> Thanks for that test case. > >> I updated the fix patch with the following. > >> diff --git a/lib/dma-debug.c b/lib/dma-debug.c >> index 42b12740940b..611010df1e9c 100644 >> --- a/lib/dma-debug.c >> +++ b/lib/dma-debug.c >> @@ -513,6 +513,13 @@ static int active_cln_insert(struct dma_debug_entry >> *entry) >> unsigned long flags; >> int rc; >> >> + /* If the device is not writing memory then we don't have any >> + * concerns about the cpu consuming stale data. This mitigates >> + * legitimate usages of overlapping mappings. >> + */ > + if (entry->>direction == DMA_TO_DEVICE) >> + return 0; >> + >> spin_lock_irqsave(&radix_lock, flags); >> rc = radix_tree_insert(&dma_active_cacheline, to_cln(entry), entry); >> if (rc == -EEXIST) >> @@ -526,6 +533,10 @@ static void active_cln_remove(struct dma_debug_entry >> *entry) >> { >> unsigned long flags; >> >> + /* ...mirror the insert case */ > + if (entry->>direction == DMA_TO_DEVICE) >> + return; >> + >> spin_lock_irqsave(&radix_lock, flags); >> /* since we are counting overlaps the final put of the >> * cacheline will occur when the overlap count is 0. > > >> Sander, barring a negative test result from you I'll send the attached >> patch to Andrew. > > Hi Dan, > > That seems to effectively suppress the warning, thanks and: > > Tested-by; Sander Eikelenboom <[email protected]>
Is there a reason this isn't in Linus' tree yet? josh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
