Re: "panic: malloc(M_WAITOK) with sleeping prohibited" at main-n245363-b3dac3913dc9

On Wed, Mar 10, 2021 at 5:37 AM David Wolfskill <david_at_catwhisker.org>
wrote:

> On Tue, Mar 09, 2021 at 04:04:56PM -0700, Warner Losh wrote:
> > On Tue, Mar 9, 2021 at 2:46 PM David Wolfskill <david_at_catwhisker.org>
> wrote:
> > ...
> > > uma_zalloc_debug: zone "malloc-1024"umass0 on uhub2
> > >  with the following non-sleepable locks held:
> > > umass0: <Bulk-In, Bulk-Out, Interface> on usbus0
> > > exclusive sleep mutex CAM device lockumass0:  SCSI over Bulk-Only;
> quirks
> > > = 0x4000
> > >  (CAM device lock) r = 0 (0xfffff800122c9cd0) locked _at_
> > > /usr/src/sys/cam/cam_xpt.c:2333
> > > umass0:6:0: Attached to scbus6
> > > stack backtrace:
> > > (probe0:umass-sim0:0:0:0): Down reving Protocol Version from 2 to 0?
> > > #0 0xffffffff80c7cce1 at witnesuhub3: 6 ports with 6 removable, self
> > > powered
> > > s_debugger+0x71
> > > pass6 at umass-sim0 bus 0 scbus6 target 0 lun 0
> > > #1 0xffffffff80pass6: uhub4: 8 ports with 8 removable, self powered
> > > c7ddfd at witness_warn+0x40d
> > > #2<Generic- Compact Flash 1.00> Removable Direct Access SCSI device
> > >  0xffffffff80f42fe6 at uma_zallpass6: Serial Number 20100818841300000
> > > oc_arg+0x46
> > > #3 0xffffffff80be34pass6: 40.000MB/s transfers
> > > panic: malloc(M_WAITOK) with sleeping prohibited
> > > cpuid = 1
> > > time = 22
> > > KDB: stack backtrace:
> > > db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame
> > > 0xfffffe00e157a2d0
> > > vpanic() at vpanic+0x181/frame 0xfffffe00e157a320
> > > panic() at panic+0x43/frame 0xfffffe00e157a380
> > > malloc_dbg() at malloc_dbg+0xd4/frame 0xfffffe00e157a3a0
> > > malloc() at malloc+0x34/frame 0xfffffe00e157a400
> > > g_post_event_x() at g_post_event_x+0x5a/frame 0xfffffe00e157a450
> > > g_post_event() at g_post_event+0x48/frame 0xfffffe00e157a4b0
> > > disk_create() at disk_create+0x16f/frame 0xfffffe00e157a600
> > > daregister() at daregister+0x70a/frame 0xfffffe00e157a880
> > > cam_periph_alloc() at cam_periph_alloc+0x57b/frame 0xfffffe00e157a950
> > > daasync() at daasync+0x2c2/frame 0xfffffe00e157a9c0
> > > xpt_async_process_dev() at xpt_async_process_dev+0x152/frame
> > > 0xfffffe00e157aa10
> > > xpt_async_process() at xpt_async_process+0x334/frame 0xfffffe00e157ab20
> > > xpt_done_process() at xpt_done_process+0x3a3/frame 0xfffffe00e157ab60
> > > xpt_done_td() at xpt_done_td+0xf5/frame 0xfffffe00e157abb0
> > > fork_exit() at fork_exit+0x80/frame 0xfffffe00e157abf0
> > > fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe00e157abf0
> > > --- trap 0, rip = 0, rsp = 0, rbp = 0 ---
> > > KDB: enter: panic
> > > [ thread pid 17 tid 100095 ]
> > > Stopped at      kdb_enter+0x37: movq    $0,0x128b8ce(%rip)
> > > db>
> > >
> > I'm willing to "poke at it" a bit, given a hint or two...
> > >
> >
> > OK. I know what's happening here. disk_create() posts an event and also
> > expects to sleep to get memory. I can fix that too, but then that's one
> > more 'no memory' hole.
> >
> > I'm unsure if we should keep playing whack-a-mole, or just defer this
> > creation to the taskqueue we already have hanging around...
> >
> > Warner
> > ....
>
> Same (build) machine had a similar panic after updating source to
> main-n245372-d1cbe7908986 & rebuilding.  FWIW.
>
> Also (as yesterday), neither laptop exhibited a problem after the
> corresponding update.
>

Yes it "works" without invariants. I'm working on a better fix that isn't
such a huge game of whack-a-mole that defers the async messages to an
taskqueue where they can sleep for memory, if need be.

Warner


> Peace,
> david
> --
> David H. Wolfskill                              david_at_catwhisker.org
> It is supremely disingenuous to claim a lack of jurisdiction, then
> proceed to participate in a decision on the same matter.
>
> See https://www.catwhisker.org/~david/publickey.gpg for my public key.
>