Re: [Qemu-devel] Qemu-KVM 0.12.3 and Multipath -> Assertion

[Kevin Wolf <kwolf@redhat.com>]

Am 04.05.2010 13:38, schrieb Peter Lieven:
> hi kevin,
> 
> i set a breakpint at bmdma_active_if. the first 2 breaks encountered 
> when the last path in the multipath
> failed, but the assertion was not true.
> when i kicked one path back in the breakpoint was reached again, this 
> time leading to an assert.
> the stacktrace is from the point shortly before.
> 
> hope this helps.

Hm, looks like there's something wrong with cancelling requests -
bdrv_aio_cancel might decide that it completes a request (and
consequently calls the callback for it) whereas the IDE emulation
decides that it's done with the request before calling bdrv_aio_cancel.

I haven't looked in much detail what this could break, but does
something like this help?

diff --git a/hw/ide/core.c b/hw/ide/core.c
index 0757528..3cd55e3 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -2838,10 +2838,6 @@ static void ide_dma_restart(IDEState *s, int is_read)
 void ide_dma_cancel(BMDMAState *bm)
 {
     if (bm->status & BM_STATUS_DMAING) {
-        bm->status &= ~BM_STATUS_DMAING;
-        /* cancel DMA request */
-        bm->unit = -1;
-        bm->dma_cb = NULL;
         if (bm->aiocb) {
 #ifdef DEBUG_AIO
             printf("aio_cancel\n");
@@ -2849,6 +2845,10 @@ void ide_dma_cancel(BMDMAState *bm)
             bdrv_aio_cancel(bm->aiocb);
             bm->aiocb = NULL;
         }
+        bm->status &= ~BM_STATUS_DMAING;
+        /* cancel DMA request */
+        bm->unit = -1;
+        bm->dma_cb = NULL;
     }
 }

Kevin