Hi Martin,
On Fri, Jun 27, 2025 at 3:34 AM Martin Pieuchot <[email protected]> wrote:
>
> On 26/06/25(Thu) 11:02, K R wrote:
> > On Wed, Jun 25, 2025 at 1:30 PM K R <[email protected]> wrote:
> > >
> > > [...]
> > > > Hi Alexander,
> > > >
> > > > The good news: I can consistently reproduce the hang problem. But the
> > > > bad news is that even with a WITNESS kernel and kern.witness.watch=2
> > > > (or even 3) I don't see any message or kernel panic.
>
> Do you mind sharing your recipe to reproduce the hang?
Sure, I'm running nfdump in a loop like this:
while :
do
nfdump -N6q -n 0 -R /path/to/flows/ -A proto,dstport \
> /dev/null 2>&1
sleep 1
done
3 instances of the above script and a large volume of netflows will do
the trick. I have set up a server for testing -- I'm happy to apply
kernel patches, provide ddb traces, etc. Please let me know how I can
help.
Thanks,
--Kor
>
> > > > Any additional suggestion in order to increase debug information or
> > > > force the machine to go into ddb?
> > >
> > > I tried a MP_LOCKDEBUG kernel and finally got a panic, shown below.
> > > Sorry for not including 'show locks' and all the cpus, but my serial
> >
> > Another hang, now with show locks:
> >
> > ddb{2}> show locks
> > exclusive rwlock amaplk r = 0 (0xfffffd9a244e4e78)
> > exclusive rwlock vmmaplk r = 0 (0xfffffd9c93c4ca90)
> > --
> > ddb{2}> ps /o
> > TID PID UID PRFLAGS PFLAGS CPU COMMAND
> > 322239 87810 0 0x3 0x4000000 0 semaphore
> > 86705 31331 0 0x3 0x4000000 11 semaphore
> > 383438 44550 0 0x3 0x4000000 14 semaphore
> > 257640 77711 0 0x3 0x4000000 13 semaphore
> > 450354 41159 0 0x3 0x4000000 7 semaphore
> > 427275 25212 0 0x3 0x4000000 12 semaphore
> > 227039 47648 0 0x3 0x4000000 8 semaphore
> > 28812 15439 0 0x3 0x4000000 6 semaphore
> > 37644 76378 0 0x100003 0 3K top
> > *305600 7089 0 0x3 0 2 nfdump
> > 192362 7089 0 0x3 0x4000000 9 nfdump
> > 160550 56545 0 0x3 0x4000000 4 nfdump
> > 367292 98858 0 0x3 0x4000000 1 nfdump
> > --
> > ddb{2}> trace
> > db_enter() at db_enter+0x14
> > pmap_do_remove(fffffd9c7aa25100,d6734d0000,d6734e0000,0) at
> > pmap_do_remove+0x4a9
> > uvm_unmap_kill_entry_withlock(fffffd9c93c4c990,fffffd9c80c83258,1) at
> > uvm_unmap_kill_entry_withlock+0x133
> > uvm_unmap_remove(fffffd9c93c4c990,d6734a0000,d6739a0000,ffff800055feaed0,0,1,7ff574ce4a271e31)
> > at uvm_unmap_remove+0x32f
> > sys_munmap(ffff8000fffe6070,ffff800055feafd0,ffff800055feaf50) at
> > sys_munmap+0x10b
> > syscall(ffff800055feafd0) at syscall+0x5f9
> > Xsyscall() at Xsyscall+0x128
> > end of kernel
> > end trace frame: 0x7365c97d4f10, count: -7
> > --
> > ddb{2}> machine ddbcpu 0
> > Stopped at x86_ipi_db+0x16: leave
> >
> > ddb{0}> trace
> > x86_ipi_db(ffffffff829e6ff0) at x86_ipi_db+0x16
> > x86_ipi_handler() at x86_ipi_handler+0x80
> > Xresume_lapic_ipi() at Xresume_lapic_ipi+0x27
> > __mp_lock(ffffffff82b2d348) at __mp_lock+0xbe
> > softintr_dispatch(0) at softintr_dispatch+0xeb
> > dosoftint(0) at dosoftint+0x3f
> > Xsoftclock() at Xsoftclock+0x27
> > end of kernel
> > end trace frame: 0x71789b60c60, count: -7
> > --
> > ddb{1}> machine ddbcpu 2
> > Stopped at db_enter+0x14: popq %rbp
> > ddb{2}> trace
> > db_enter() at db_enter+0x14
> > pmap_do_remove(fffffd9c7aa25100,d6734d0000,d6734e0000,0) at
> > pmap_do_remove+0x4a9
> > uvm_unmap_kill_entry_withlock(fffffd9c93c4c990,fffffd9c80c83258,1) at
> > uvm_unmap_kill_entry_withlock+0x133
> > uvm_unmap_remove(fffffd9c93c4c990,d6734a0000,d6739a0000,ffff800055feaed0,0,1,7ff574ce4a271e31)
> > at uvm_unmap_remove+0x32f
> > sys_munmap(ffff8000fffe6070,ffff800055feafd0,ffff800055feaf50) at
> > sys_munmap+0x10b
> > syscall(ffff800055feafd0) at syscall+0x5f9
> > Xsyscall() at Xsyscall+0x128
> > end of kernel
> > end trace frame: 0x7365c97d4f10, count: -7
> > --
> >
> > > console session froze before that.
> > >
> > > Hope it helps,
> > > --Kor
> > >
> > > pmap_tlb_shootwait: spun out
> > > Stopped at db_enter+0x14: popq %rbp
> > > ddb{13}>
> > > --
> > > ddb{13}> show panic
> > > the kernel did not panic
> > > --
> > > ddb{13}> ps /o
> > > TID PID UID PRFLAGS PFLAGS CPU COMMAND
> > > 307801 52176 0 0x2 0x4000000 10 semaphore
> > > 410431 54690 0 0x2 0x4000000 15 semaphore
> > > 257513 26918 0 0x2 0x4000000 11 semaphore
> > > 138054 68532 0 0x2 0x4000000 5 semaphore
> > > 203059 2408 0 0x2 0x4000000 9 semaphore
> > > 89141 5998 0 0x2 0x4000000 8 semaphore
> > > 263439 99498 0 0x2 0x4000000 7 semaphore
> > > 477129 15941 0 0x2 0x4000000 12 semaphore
> > > 41845 21800 0 0x3 0x4000000 2 nfdump
> > > 371022 21800 0 0x3 0x4000000 0 nfdump
> > > *391905 66338 0 0x3 0x4000000 13 nfdump
> > > 367615 66338 0 0x3 0x4000000 6 nfdump
> > > 394180 56727 0 0x3 0x4000000 3 nfdump
> > > 46184 33300 0 0x100003 0 1K top
> > > --
> > > ddb{13}> trace
> > > db_enter() at db_enter+0x14
> > > pmap_page_remove(fffffd8184bdc408) at pmap_page_remove+0x38e
> > > uvm_anfree_list(fffffd9c88e2be50,0) at uvm_anfree_list+0x63
> > > amap_wipeout(fffffd9ca390fc88) at amap_wipeout+0x198
> > > uvm_unmap_detach(ffff80005608fcc0,0) at uvm_unmap_detach+0xbe
> > > sys_munmap(ffff800055cda540,ffff80005608fdc0,ffff80005608fd40) at
> > > sys_munmap+0x185
> > > syscall(ffff80005608fdc0) at syscall+0x5f9
> > > Xsyscall() at Xsyscall+0x128
> > > end of kernel
> > > end trace frame: 0x123cf0e2b80, count: -8
> > > --
> > > ddb{13}> machine ddbcpu 1
> > > Stopped at x86_ipi_db+0x16: leave
> > >
> > > ddb{1}> trace
> > > x86_ipi_db(ffff8000552aaff0) at x86_ipi_db+0x16
> > > x86_ipi_handler() at x86_ipi_handler+0x80
> > > Xresume_lapic_ipi() at Xresume_lapic_ipi+0x27
> > > pmap_enter(fffffd9cd8988d00,7103880b6000,1c7767a000,3,33) at
> > > pmap_enter+0x703
> > > uvm_fault_upper(ffff800055da4928,ffff800055da4960,ffff800055da4820) at
> > > uvm_fault_upper+0x1e0
> > > uvm_fault(fffffd9ca1ab8b58,7103880b6000,2,3) at uvm_fault+0xce
> > > uvm_fault_wire(fffffd9ca1ab8b58,7103880b6000,7103880b7000,3) at
> > > uvm_fault_wire+0x58
> > > uvm_map_pageable_wire(fffffd9ca1ab8b58,fffffd9c8f522700,fffffd9ca0915ab8,0,3,0)
> > > at uvm_map_pageable_wire+0x19d
> > > sysctl_vslock(7103880b6d68,18) at sysctl_vslock+0x9b
> > > sys_sysctl(ffff800055d61c60,ffff800055da4c80,ffff800055da4c00) at
> > > sys_sysctl+0x187
> > > syscall(ffff800055da4c80) at syscall+0x5f9
> > > Xsyscall() at Xsyscall+0x128
> > > end of kernel
> > > end trace frame: 0x7103880b6dc0, count: -12
> > > --
> > >
> > > [...]
> >
>
>
