r244036 kernel hangs under load.
Rick Macklem
rmacklem at uoguelph.ca
Tue Dec 11 00:12:01 UTC 2012
Konstantin Belousov wrote:
> On Mon, Dec 10, 2012 at 01:38:21PM -0500, Rick Macklem wrote:
> > Adrian Chadd wrote:
> > > .. what was the previous kernel version?
> > >
> > Hopefully Tim has it narrowed down more, but I don't see
> > the hangs on a Sept. 7 kernel from head and I do see them
> > on a Dec. 3 kernel from head. (Don't know the eact rNNNNNN.)
> >
> > It seems to predate my commit (r244008), which was my first
> > concern.
> >
> > I use old single core i386 hardware and can fairly reliably
> > reproduce it by doing a kernel build and a "svn checkout"
> > concurrently. No NFS activity. These are running on a local
> > disk (UFS/FFS). (The kernel I reproduce it on is built via
> > GENERIC for i386. If you want me to start a "binary search"
> > for which rNNNNNN, I can do that, but it will take a while.:-)
> >
> > I can get out into DDB, but I'll admit I don't know enough
> > about it to know where to look;-)
> > Here's some lines from "db> ps", in case they give someone
> > useful information. (I can leave this box sitting in DB for
> > the rest of to-day, in case someone can suggest what I should
> > look for on it.)
> >
> > Just snippets...
> > Ss pause adjkerntz
> > DL sdflush [sofdepflush]
> > RL [syncer]
> > DL vlruwt [vnlru]
> > DL psleep [bufdaemon]
> > RL [pagezero]
> > DL psleep [vmdaemon]
> > DL psleep [pagedaemon]
> > DL ccb_scan [xpt_thrd]
> > DL waiting_ [sctp_iterator]
> > DL ctl_work [ctl_thrd]
> > DL cooling [acpi_cooling0]
> > DL tzpoll [acpi_thermal]
> > DL (threaded) [usb]
> > ...
> > DL - [yarrow]
> > DL (threaded) [geom]
> > D - [g_down]
> > D - [g_up]
> > D - [g_event]
> > RL (threaded) [intr]
> > I [irq15: ata1]
> > ...
> > Run CPU0 [swi6: Giant taskq]
> > --> does this one indicate the CPU is actually running this?
> > (after a db> cont, wait a while <ctrl><alt><esc> db> ps
> > it is still the same)
> > I [swi4: clock]
> > I [swi1: netisr 0]
> > I [swi3: vm]
> > RL [idle: cpu0]
> > SLs wait [init]
> > DL audit_wo [audit]
> > DLs (threaded) [kernel]
> > D - [deadlkres]
> > ...
> > D sched [swapper]
> >
> > I have no idea if this "ps" output helps, unless it indicates
> > that it is looping on the Giant taskq?
> Might be. You could do 'bt <pid>' for the process to see where it
> loops.
> Another good set of hints is at
> http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug-deadlocks.html
Kostik, you must be clairvoyant;-)
When I did "show alllocks", I found that the syncer process held
- exclusive sleep mutex mount mtx locked @ kern/vfs_subr.c:4720
- exclusive lockmgr syncer locked @ kern/vfs_subr.c:1780
The trace for this process goes like:
spinlock_exit
mtx_unlock_spin_flags
kern_yield
_mnt_vnode_next_active
vnode_next_active
vfs_msync()
So, it seems like your r244095 commit might have fixed this?
(I'm not good at this stuff, but from your description, it looks
like it did the kern_yield() with the mutex held and "maybe"
got into trouble trying to acquire Giant?)
Anyhow, I'm going to test a kernel with r244095 in it and see
if I can still reproduce the hang.
(There wasn't much else in the "show alllocks", except a
process that held the exclusive vnode interlock mutex plus
a ufs vnode lock, but it's just doing a witness_unlock.)
I'll email if/when I know more, rick
ps: Fingers/toes crossed that you've already fixed it.
>
> >
> > As I said, I can leave it in "db" for to-day, if anyone wants
> > me to do anything in the debugger and I can probably reproduce
> > it, if someone wants stuff tried later.
> >
> > rick
> >
> >
> > >
> > >
> > > adrian
> > >
> > >
> > > On 9 December 2012 22:08, Tim Kientzle <kientzle at freebsd.org>
> > > wrote:
> > > > I haven't found any useful clues yet, but thought I'd ask if
> > > > anyone
> > > > else
> > > > was seeing hangs in a recent kernel.
> > > >
> > > > I just upgraded to r244036 using a straight GENERIC i386 kernel.
> > > > (Straight buildworld/buildkernel, no local changes,
> > > > /etc/src.conf
> > > > doesn't
> > > > exist, /etc/make.conf just has PERL_VERSION defined.)
> > > >
> > > > When I try to cross build an ARM world on the resulting system,
> > > > the entire system hangs hard after about 30 minutes: No network,
> > > > no keyboard response, no nothing.
> > > >
> > > > Don't know if it's relevant, but the system is using NFS pretty
> > > > heavily (Parallels VM mounting NFS from Mac OS 10.7 host.)
> > > >
> > > > I'll try to get some more details ...
> > > >
> > > > Tim
> > > >
> > > > _______________________________________________
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