Re: OOPS in idescsi_end_request

[Brian King <brking@charter.net>]

Can the interrupt handler even look at the request structure in this 
scenario though? I can't say I know much about the ide subsystem but it 
seems like after ide-scsi returns success on the reset function then it 
should have already pushed scsi_done for the op and should not be 
looking at the request structure. Would it be possible to have the 
ide-scsi reset routine invoke ide_do_reset? Is there a problem with 
multiple callers of ide_do_reset? I would think the right solution would 
be to do this and not return success until the reset was successful and 
the op was sent back to the mid-layer.

-Brian


Andrey Borzenkov wrote:
> 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
> 
> 
> 


-- 
Some days it's just not worth chewing through the restraints...