if_sge related panics

[Pyun YongHyeon]

On Fri, Jun 04, 2010 at 07:52:19AM +0300, Nikolay Denev wrote:
> 
> On Jun 4, 2010, at 3:35 AM, Pyun YongHyeon wrote:
> 
> > On Thu, Jun 03, 2010 at 09:29:20AM +0300, Nikolay Denev wrote:
> >> On May 24, 2010, at 8:12 PM, Pyun YongHyeon wrote:
> >> 
> >>> On Mon, May 24, 2010 at 09:48:33AM -0400, John Baldwin wrote:
> >>>> On Monday 24 May 2010 6:35:01 am Nikolay Denev wrote:
> >>>>> On May 24, 2010, at 8:57 AM, Nikolay Denev wrote:
> >>>>> 
> >>>>>> Hi,
> >>>>>> 
> >>>>>> Recently I started to experience a if_sge(4) related panic.
> >>>>>> It happens almost every time I try to download a torrent file for example.
> >>>>>> Copying of large files over NFS seem not to trigger it, but I haven't tested extensively.
> >>>>>> 
> >>>>>> Here is the panic message :
> >>>>>> 
> >>>>>> Fatal trap 12: page fault while in kernel mode
> >>>>>> cpuid = 0; apic id = 00
> >>>>>> fault virtual address		= 0x8
> >>>>>> fault code				= supervisor write data, page not present
> >>>>>> instruction pointer		= 0x20:0xffffffff80230413
> >>>>>> stack pointer				= 0x28:0xffffff80001e9280
> >>>>>> frame pointer			= 0x28:0xffffff80001e9510
> >>>>>> code segment			= base 0x0, limit 0xfffff, type 0x1b
> >>>>>> 						= DPL 0, pres 1, long 1, def32 0, gran 1
> >>>>>> processor eflags			= interrupt enabled, resume, IOPL = 0
> >>>>>> current process			= 12 (irq19: sge0)
> >>>>>> trap number				= 12
> >>>>>> panic: page fault
> >>>>>> cpuid = 0
> >>>>>> Uptime: 1d20h56m20s
> >>>>>> Cannot dump. Device not defined or unavailable
> >>>>>> Automatic reboot in 15 seconds - press a key on the console to abort
> >>>>>> Sleeping thread (tid 100039, pid 12) owns a non-sleepable lock
> >>>>>> 
> >>>>>> My swap is on a zvol, so I don't have dump. I'll try to attach a disk on the eSATA port and dump there if needed.
> >>>>> 
> >>>>> Here is some info from the crashdump :
> >>>>> 
> >>>>> (kgdb) #0  doadump () at pcpu.h:223
> >>>>> #1  0xffffffff802fb149 in boot (howto=260)
> >>>>>   at /usr/src/sys/kern/kern_shutdown.c:416
> >>>>> #2  0xffffffff802fb57c in panic (fmt=0xffffffff8055d564 "%s")
> >>>>>   at /usr/src/sys/kern/kern_shutdown.c:590
> >>>>> #3  0xffffffff805055b8 in trap_fatal (frame=0xffffff000288a3e0, eva=Variable "eva" is not available.
> >>>>> )
> >>>>>   at /usr/src/sys/amd64/amd64/trap.c:777
> >>>>> #4  0xffffffff805059dc in trap_pfault (frame=0xffffff80001e91d0, usermode=0)
> >>>>>   at /usr/src/sys/amd64/amd64/trap.c:693
> >>>>> #5  0xffffffff805061c5 in trap (frame=0xffffff80001e91d0)
> >>>>>   at /usr/src/sys/amd64/amd64/trap.c:451
> >>>>> #6  0xffffffff804eb977 in calltrap ()
> >>>>>   at /usr/src/sys/amd64/amd64/exception.S:223
> >>>>> #7  0xffffffff80230413 in sge_start_locked (ifp=0xffffff000270d800)
> >>>>>   at /usr/src/sys/dev/sge/if_sge.c:1591
> >>>> 
> >>>> Try this.  sge_encap() can sometimes return an error with m_head set to NULL:
> >>>> 
> >>> 
> >>> Thanks John. Committed in r208512.
> >>> 
> >>>> Index: if_sge.c
> >>>> ===================================================================
> >>>> --- if_sge.c	(revision 208375)
> >>>> +++ if_sge.c	(working copy)
> >>>> @@ -1588,7 +1588,8 @@
> >>>> 		if (m_head == NULL)
> >>>> 			break;
> >>>> 		if (sge_encap(sc, &m_head)) {
> >>>> -			IFQ_DRV_PREPEND(&ifp->if_snd, m_head);
> >>>> +			if (m_head != NULL)
> >>>> +				IFQ_DRV_PREPEND(&ifp->if_snd, m_head);
> >>>> 			ifp->if_drv_flags |= IFF_DRV_OACTIVE;
> >>>> 			break;
> >>>> 		}
> >>>> 
> >>>> -- 
> >>>> John Baldwin
> >> 
> >> After the patch I experienced several network outages (ping reporting "no buffer space available")
> >> that were resolved by ifconfig down/up of the sge(4) interface.
> >> 
> > 
> > Because I don't have access to sge(4) controllers I never had chance
> > to run it. Does ping(8) generates "no buffer space available" when
> > the system is in idle state? Could you show me more information on
> > how you checked network outages?
> > 
> 
> It happened 4-5 times recently. I didn't do extensive investigation, but yes, ping
> returned "no buffer space avail" when I tried pinging from the machine itself.
> It was unreachable from other hosts on the network.
> I'm not sure what you bean by idle state but there was a torrent client running
> on the machine, which printed errors about inability to reach peers.
> 

If system is under heavy TX load(e.g. 64bytes UDP test), ping(8)
may show that message.

> 
> >> I can see that most of the other drivers that handle XXX_encap() returning m_head pointing NULL, break when this condition
> > 
> > Yes, most drivers written/touched by me behaves like that.
> > 
> >> is hit: i.e. :
> >> 
> >> Index: if_sge.c
> >> ===================================================================
> >> --- if_sge.c	(revision 208375)
> >> +++ if_sge.c	(working copy)
> >> @@ -1588,7 +1588,8 @@
> >> 		if (m_head == NULL)
> >> 			break;
> >> 		if (sge_encap(sc, &m_head)) {
> >> -			IFQ_DRV_PREPEND(&ifp->if_snd, m_head);
> >> +			if (m_head == NULL)
> >> +				break;
> >> 			IFQ_DRV_PREPEND(&ifp->if_snd, m_head);
> >> 			ifp->if_drv_flags |= IFF_DRV_OACTIVE;
> >> 			break;
> >> 		}
> >> 
> >> But here in sge(4) we always set IFF_DRV_OACTIVE.
> >> Do you think this can be the source of the problem ?
> >> 
> > 
> > More correct way to set IFF_DRV_OACTIVE would be check the number
> > of queued frames or just exit the transmit loop. If there is no
> > queued frames, IFF_DRV_OACTIVE would never be cleared which in turn
> > cause ENOBUFS in ping(8). I think your change looks more reasonable
> > to me. Do you still see the same issue with the change you suggested?
> 
> I'm runing with this change for a day or something now without any issues.

Ok, committed in r208806.
Thanks for the patch.