On Wed, Oct 17 2007, Ingo Molnar wrote:
quoted text
> 
> ok, here's a different but similar crash that triggers on the testbox:
> 
> [  233.438890] BUG: unable to handle kernel paging request at virtual address 7d93e000
> [  233.446390] printing eip: 784e9480 *pde = 01000067 *pte = 0593e000 
> [  233.452630] Oops: 0000 [#1] DEBUG_PAGEALLOC
> [  233.456790] 
> [  233.458264] Pid: 0, comm: swapper Not tainted (2.6.23 #5)
> [  233.463637] EIP: 0060:[<784e9480>] EFLAGS: 00010087 CPU: 0
> [  233.469101] EIP is at ata_qc_issue+0x90/0x380
> [  233.473429] EAX: 7d93dff0 EBX: 0000001f ECX: 7d93dff0 EDX: 798daf80
> [  233.479668] ESI: 00000020 EDI: 7d93de00 EBP: 7b54007c ESP: 78a13e14
> [  233.485908]  DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068
> [  233.491282] Process swapper (pid: 0, ti=78a12000 task=789753e0 task.ti=78a12000)
> [  233.498473] Stack: 7d93de00 7b540000 7b540000 00000000 7d93dfe0 7b54007c 7d93db00 7b5417a4 
> [  233.506793]        784c2490 784ef69e 784f21f3 7b52de98 7d93db00 7b540000 7b5417a4 7d93db00 
> [  233.515112]        7b540000 7b524004 784f22e0 784ef380 784c2490 7d93db00 00000202 7b524004 
> [  233.523432] Call Trace:
> [  233.526033]  [<784c2490>] scsi_done+0x0/0x20
> [  233.530279]  [<784ef69e>] ata_scsi_translate+0xbe/0x140
> [  233.535478]  [<784f21f3>] ata_scsi_queuecmd+0x33/0x200
> [  233.540591]  [<784f22e0>] ata_scsi_queuecmd+0x120/0x200
> [  233.545791]  [<784ef380>] ata_scsi_rw_xlat+0x0/0x220
> [  233.550730]  [<784c2490>] scsi_done+0x0/0x20
> [  233.554976]  [<784c2d12>] scsi_dispatch_cmd+0x152/0x290
> [  233.560177]  [<78135c67>] trace_hardirqs_on+0x67/0xb0
> [  233.565202]  [<784c8c7e>] scsi_request_fn+0x1be/0x370
> [  233.570229]  [<78408086>] blk_run_queue+0x36/0x80
> [  233.574909]  [<784c7520>] scsi_next_command+0x30/0x50
> [  233.579935]  [<784c76ab>] scsi_end_request+0xab/0xe0
> [  233.584875]  [<784c83f9>] scsi_io_completion+0xa9/0x3d0
> [  233.590075]  [<78135c67>] trace_hardirqs_on+0x67/0xb0
> [  233.595100]  [<78405125>] blk_done_softirq+0x45/0x80
> [  233.600040]  [<78405153>] blk_done_softirq+0x73/0x80
> [  233.604981]  [<7811d4c3>] __do_softirq+0x53/0xb0
> [  233.609573]  [<7811d588>] do_softirq+0x68/0x70
> [  233.613993]  [<78105351>] do_IRQ+0x51/0x90
> [  233.618066]  [<78135c9c>] trace_hardirqs_on+0x9c/0xb0
> [  233.623092]  [<7810f2d0>] pgd_dtor+0x0/0x50
> [  233.627252]  [<7810388e>] common_interrupt+0x2e/0x40
> [  233.632192]  [<7810f2d0>] pgd_dtor+0x0/0x50
> [  233.636352]  [<7815f3be>] quicklist_trim+0x5e/0x90
> [  233.641118]  [<7810f2cb>] check_pgt_cache+0x1b/0x20
> [  233.645971]  [<78100c52>] cpu_idle+0x32/0x60
> [  233.650217]  [<78a14b35>] start_kernel+0x265/0x300
> [  233.654983]  [<78a14380>] unknown_bootoption+0x0/0x1e0
> [  233.660097]  =======================
> [  233.663649] Code: 00 00 00 8b 45 34 a8 02 0f 84 ed 00 00 00 8b bd 88 00 00 00 31 db 89 3c 24 8b 75 3c 89 f8 c7 44 24 10 00 00 00 00 eb 1b 8d 76 00 <8b> 50 10 8d 48 10 f6 c2 01 0f 85 be 02 00 00 89 44 24 10 83 c3 
> [  233.682455] EIP: [<784e9480>] ata_qc_issue+0x90/0x380 SS:ESP 0068:78a13e14
> [  233.689302] Kernel panic - not syncing: Fatal exception in interrupt
> 
> (gdb) list *0x784e9480
> 0x784e9480 is in ata_qc_issue (include/linux/scatterlist.h:48).
> 43       */
> 44      static inline struct scatterlist *sg_next(struct scatterlist *sg)
> 45      {
> 46              sg++;
> 47
> 48              if (unlikely(sg_is_chain(sg)))
> 49                      sg = sg_chain_ptr(sg);
> 50
> 51              return sg;
> 52      }
> (gdb)
> 
> so there's sg_next() involvement too. Below is the disassembly.

You must have a magic test box :-)

Will investigate... libata doesn't actually enable chaining, but since
i386 supports it, it ends up using the chain helpers anyway.

There seems to be some automatic inlining involved here, it must be
dying inside ata_sg_setup().

-- 
Jens Axboe

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