Messages in this thread Patch in this message | | | Subject | Re: Linux 2.5.44-ac1 | From | Jason Williams <> | Date | 23 Oct 2002 07:39:35 -0400 |
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On Tue, 2002-10-22 at 13:27, Alan Cox wrote: > ** I strongly recommend saying N to IDE TCQ options otherwise this > should hopefully build and run happily.
I don't have the IDE TCQ options on and am still having an issue with a kernel oops in the default kernel code. I did some digging after I noticed it in 2.5.43 and found a possibility for a null pointer in the code within the ide_iomio_dma function in ide-dma.c The problem shows itself if you only enable the secondary channel of your IDE controller. I understand this is a strange set up, but it could happen in a machine that boots off of SCSI and uses IDE disks for DATA or a CD Burner. I came up with a fix, some extra sanity checks before this line in the code:
hwif->dma_master = (hwif->channel) ? hwif->mate->dma_base : base;
Because it is the hwif->mate variable that is null when it gets here and if hwif->channel is not 0 I am taking it from the logic on this line that hwif->mate should not be a null variable. So I applied the sainity checks in the attached patch and this seems to work. I did this against the 2.5.43 and 2.5.44 kernels, and have posted patches for each of them but no one seems interested. If I am completely off base here, just let me know and I'll go back to the code and look for a different way to conquer this little bug.
Jason
diff -u -r linux-2.5.44-vanilla/drivers/ide/ide-dma.c linux-2.5.44/drivers/ide/ide-dma.c --- linux-2.5.44-vanilla/drivers/ide/ide-dma.c 2002-10-21 08:02:49.000000000 -0500 +++ linux-2.5.44/drivers/ide/ide-dma.c 2002-10-21 08:56:49.000000000 -0500 @@ -905,7 +905,12 @@ request_region(base+16, hwif->cds->extra, hwif->cds->name); hwif->dma_extra = hwif->cds->extra; } - hwif->dma_master = (hwif->channel) ? hwif->mate->dma_base : base; + if(!hwif->mate && hwif->channel){ + hwif->dma_master=base; + } + else{ + hwif->dma_master = (hwif->channel) ? hwif->mate->dma_base : base; + } if (hwif->dma_base2) { if (!check_mem_region(hwif->dma_base2, ports)) request_mem_region(hwif->dma_base2, ports, hwif->name); @@ -925,8 +930,13 @@ if ((hwif->cds->extra) && (hwif->channel == 0)) { request_region(base+16, hwif->cds->extra, hwif->cds->name); hwif->dma_extra = hwif->cds->extra; + } + if(!hwif->mate && hwif->channel){ + hwif->dma_master=base; + } + else{ + hwif->dma_master = (hwif->channel) ? hwif->mate->dma_base : base; } - hwif->dma_master = (hwif->channel) ? hwif->mate->dma_base : base; if (hwif->dma_base2) { if (!request_region(hwif->dma_base2, ports, hwif->name)) {
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