Re: OOPS in idescsi_end_request

["Andrey Borzenkov" <arvidjaar@mail.ru>]

As long as we cannot easily abort IDE request (correct me if I am wrong) the workaround seems to be to mark current request as aborted in idescsi_abort and ignore it later in idescsi_end_request, i.e. something like (with new flag PC_ABORTED)

struct request *rq = HWGROUP(idescsi_drives[cmd->target])->rq;
idescsi_pc_t *pc = (idescsi_pc_t *) rq->buffer;
pc->flags |= PC_ABORTED;

and later on assume we can ignore SCSI layer completely in this case in idescsi_end_request, just do general cleanup.

If you can reliably reproduce the problem you could give it a try.

Anybody sees yet another race condition here? :))

-andrey 

> While burning a CD tonight I ended up taking an oops on my system. I had 
> the lkcd patch applied to my 2.4.19 kernel, so I was able to look at the 
>   oops after my system rebooted. After digging into it a little and 
> looking at the ide-scsi code I think I found the problem but am not 
> sure. How can idescsi_reset simply return SCSI_RESET_SUCCESS to the scsi 
> mid layer? I think what is happening is that a command times out, 
> idescsi_abort is called, which returns SCSI_ABORT_SNOOZE. Later on 
> idescsi_reset gets called, which returns SCSI_RESET_SUCCESS. At this 
> point the scsi mid-layer owns the scsi_cmnd and returns the failure back 
> up the chain. Later on, the command gets run through 
> idescsi_end_request, which then tries to access the scsi_cmnd structure 
> which is it no longer owns.
> 
> Any help is appreciated. I have a complete lkcd dump of the failure if 
> anyone would like more information...
> 
> -Brian King
> 
> 
> Here is the last bit in the log buffer:
> 
>      <4>scsi : aborting command due to timeout : pid 2534304, scsi0, 
> channel 0, id 1, lun 0 Write (10) 00 00 01 1e 91 00 00 1b 00
>      <4>hdk: timeout waiting for DMA
>      <4>ide_dmaproc: chipset supported ide_dma_timeout func only: 14
>      <4>hdk: status timeout: status=0xd8 { Busy }
>      <4>hdk: drive not ready for command
>      <4>hdk: ATAPI reset complete
>      <4>hdk: irq timeout: status=0x80 { Busy }
>      <4>hdk: ATAPI reset complete
>      <4>hdk: irq timeout: status=0x80 { Busy }
>      <1>Unable to handle kernel NULL pointer dereference at virtual 
> address 00000184
>      <4> printing eip:
>      <4>e0fd22f1
>      <1>*pde = 00000000
>      <4>Oops: 0002
>      <4>CPU:    0
>      <4>EIP:    0010:[<e0fd22f1>]    Tainted: PF
>      <4>EFLAGS: 00010046
>      <4>eax: 00000000   ebx: 00000000   ecx: dfef8000   edx: c75bcbc0
>      <4>esi: 00000080   edi: c0491938   ebp: d5908000   esp: c0435ea4
>      <4>ds: 0018   es: 0018   ss: 0018
>      <4>Process swapper (pid: 0, stackpage=c0435000)
>      <4>Stack: c0491938 00000000 00000000 c0491938 00000088 000001f4 
> c03349e2 c75bcbc0
>      <4>       ce0a3b80 c0491938 00000080 00000080 c75bcbc0 c0222d6c 
> 00000000 c1671580
>      <4>       00000080 c04918f4 c0491938 c0434000 c1671580 e0fd2550 
> c0223b30 c0491938
>      <4>Call Trace:    [<c0222d6c>] [<e0fd2550>] [<c0223b30>] 
> [<c0223990>] [<c0127af0>]
>      <4>  [<c01233d4>] [<c01232a6>] [<c01230ed>] [<c010a97f>] 
> [<c010d173>] [<c0106f80>]
>      <4>  [<c0106fa3>] [<c0107012>] [<c0105000>]
>      <4>
>      <4>Code: c7 80 84 01 00 00 00 00 07 00 75 72 9c 5e fa bb 00 e0 ff ff
> 
> 
>  From lkcd:
> 
> ================================================================
> STACK TRACE FOR TASK: 0xc0434000 (swapper)
> 
>   0 [ide-scsi]idescsi_end_request+129 [0xe0fd22f1]
> TRACE ERROR 0x800000000