On Mon, 24 Nov 2008, James Bottomley wrote: > On Mon, 2008-11-24 at 18:43 +0100, Thomas Gleixner wrote: > > > scsi0 : LSI SAS based MegaRAID driver > > > Driver 'sd' needs updating - please use bus_type methods > > > scsi 0:0:0:0: Direct-Access ATA SAMSUNG HE160HJ 0-24 PQ: 0 ANSI: 5 > > > ------------[ cut here ]------------ > > > WARNING: at lib/debugobjects.c:215 debug_print_object+0x4f/0x57() > > > ODEBUG: free active object type: timer_list > > > > That's the cause for your boot crash. The scsi/blk code is freeing a > > page which contains an active timer, so the timer code references gone > > memory. You triggered it because DEBUG_PAGEALLOC unmaps the page when > > it's freed. > > > > James, or other scsi experts please. > > Well, not sure. Most likely candidate is the new block timer code. > What seems to be happening is that the queue is being released with > either an outstanding request (refcounting problem) or ticking timer > with no work (block timer problem). The way scanning works is that we > create a request queue for each device we probe and then delete it again > if nothing appears after the bus settle time. The argument against > this is that it should show up on every scanned bus. However, these are > getting rarer; I was just about to write that I hadn't seen it when I > remembered that all my SCSI testing systems are currently running > hotplug reporting busses (i.e. don't do scanning). However, > fortunately, I've also booted voyager recently which does use parallel > SCSI and doesn't see this either, so it could also be megaraid_sas > specific. Yeah, block could it be as well. Jens, Mike ? One note about not seeing it: We have had such bugs before where the page was freed but not touched and the timer survived w/o tripping the system over. Alexander noticed because of DEBUG_PAGEALLOC and you can also see it by enabling debugobjects, which will give you the nice backtrace. CONFIG_DEBUG_OBJECTS=y CONFIG_DEBUG_OBJECTS_FREE=y CONFIG_DEBUG_OBJECTS_TIMERS=Y and add "debug_objects" to the kernel command line. > Could you turn on SCSI logging so we can see the sequences. Probably > since this is boot time, just enable all logging: > > echo 0xffffffff > /sys/module/scsi_mod/parameters/scsi_logging_level > > (kernel must be compiled with CONFIG_SCSI_LOGGING=y > > James > > -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
