ATA READ command timeout (and worse)

[Stephen McKay]

On Tuesday, 17th June 2003, Jaw-Shiang Joshua Huang wrote:

>Because your machine will reboot automatically when the disk driver operation
>is abnormal, it makes me want to know more.
>
>Is your kernel compiled with DDB?  If not, it will reboot after 15 seconds
>while hitting panic.  If it's reproducable, would you mind to compile a new 
>kernel and try to find out where it panic or page fault?  I just want to know
>this bug will make FreeBSD kernel reboot or just hit panic or page fault.

I recompiled the kernel with DDB.  A few test runs and I got this:

Jun 18 19:19:44 peon /kernel: ad4: no status, reselecting device
Jun 18 19:19:44 peon /kernel: ad4: timeout sending command=c8 s=ff e=00
Jun 18 19:19:44 peon /kernel: ad4: error executing command - resetting
Jun 18 19:19:44 peon /kernel: ata2: resetting devices .. 
Jun 18 19:19:44 peon /kernel: ad4: removed from configuration
Jun 18 19:19:44 peon /kernel: ad5: removed from configuration
Jun 18 19:19:44 peon /kernel: done

Fatal trap 12: page fault while in kernel mode
fault virtual address   = 0x63657865
fault code              = supervisor read, page not present
instruction pointer     = 0x8:0xc0164cd9
stack pointer           = 0x10:0xc02bd438
frame pointer           = 0x10:0xc02bd4c0
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = Idle
interrupt mask          =
kernel: type 12 trap, code=0
Stopped at      kvprintf+0x545: repne scasb     (%esi)
db> trace
kvprintf(c028add6,c016456c,c02bd4e0,a,c02bd4fc) at kvprintf+0x545
printf(c028add4,63657865,c1246800,c02bd528,c012d908) at printf+0x44
ata_prtdev(c139a400,c028d280,c028d271,5b512a0,0,0) at ata_prtdev+0x1a
ad_timeout(c13bb200,400000,0,0,ffffffff) at ad_timeout+0x40
softclock(0,10,10,10,ffffffff) at softclock+0xd1
doreti_swi(e,665,2,183f9ff,756e6547) at doreti_swi+0xf
idle_loop() at idle_loop+0x1d
db>

Obviously 0x63657865 is suspicious.  On further investigation, the
ata_device structure at 0xc139a400 has been corrupted.  The unit and
subsequent fields have been replace by the text string "/libexec/ld-elf.so.1"
which is odd, to say the least.

Now I don't know what I'm chasing: a random VM bug, bad memory, PCI bus
errors, sagging power, bugs in the ata driver, cosmic rays, space aliens.

It's been a long time since I've had to do any kernel debugging, but I
suppose I'll have to set up a serial console and get to it.

Stephen.