Kernel panic when reboot on server with a Promise SX4000 and two ATA disks RAID1.

[Alexander Motin]

Magnus Kling wrote:
> Addr2line gives me /usr/src/sys/dev/ata/chipsets/ata-promise.c:1066
> 
> struct ata_dma_prdentry *prd = request->dma->sg;
> 
> Can we do an if statement with pointer prd? Or check what "sg" is at the 
> moment? What is "sg"?

A-ha! That explains a lot! I have got it!

Flush command has no data and does not uses DMA. Dereference of NULL 
request->dma pointer crashes the system. That dereference is just not 
needed there. Try please attached patch.

-- 
Alexander Motin
-------------- next part --------------
--- ata-promise.c.prev	2009-05-20 01:24:31.000000000 +0300
+++ ata-promise.c	2009-05-20 09:51:13.000000000 +0300
@@ -1054,7 +1054,7 @@ ata_promise_sx4_command(struct ata_reque
     device_t gparent = GRANDPARENT(request->dev);
     struct ata_pci_controller *ctlr = device_get_softc(gparent);
     struct ata_channel *ch = device_get_softc(request->parent);
-    struct ata_dma_prdentry *prd = request->dma->sg;
+    struct ata_dma_prdentry *prd;
     caddr_t window = rman_get_virtual(ctlr->r_res1);
     u_int32_t *wordp;
     int i, idx, length = 0;
@@ -1098,6 +1098,7 @@ ata_promise_sx4_command(struct ata_reque
     case ATA_READ_DMA48:
     case ATA_WRITE_DMA:
     case ATA_WRITE_DMA48:
+	prd = request->dma->sg;
 	wordp = (u_int32_t *)
 	    (window + (ch->unit * ATA_PDC_CHN_OFFSET) + ATA_PDC_HSG_OFFSET);
 	i = idx = 0;