r358252 causes intermittent hangs where processes are stuck sleeping on btalloc
Rick Macklem
rmacklem at uoguelph.ca
Fri May 22 23:46:30 UTC 2020
Konstantin Belousov wrote:
>On Wed, May 20, 2020 at 11:58:50PM -0700, Ryan Libby wrote:
>> On Wed, May 20, 2020 at 6:04 PM Rick Macklem <rmacklem at uoguelph.ca> wrote:
>> >
>> > Hi,
>> >
>> > Since I hadn't upgraded a kernel through the winter, it took me a while
>> > to bisect this, but r358252 seems to be the culprit.
>> >
>> > If I do a kernel build over NFS using my not so big Pentium 4 (single core,
>> > 1.25Gbytes RAM, i386), about every second attempt will hang.
>> > When I do a "ps" in the debugger, I see processes sleeping on btalloc.
>> > If I revert to r358251, I cannot reproduce this.
>> >
>> > Any ideas?
>> >
>> > I can easily test any change you might suggest to see if it fixes the
>> > problem.
>> >
>> > If you want more debug info, let me know, since I can easily
>> > reproduce it.
>> >
>> > Thanks, rick
>>
>> Nothing obvious to me. I can maybe try a repro on a VM...
>>
>> ddb ps, acttrace, alltrace, show all vmem, show page would be welcome.
>>
>> "btalloc" is "We're either out of address space or lost a fill race."
>
>Yes, I would be not surprised to be out of something on 1G i386 machine.
>Please also add 'show alllocks'.
Ok, I used an up to date head kernel and it took longer to reproduce a hang.
This time, none of the processes are stuck on "btalloc".
I'll try and give you most of the above, but since I have to type it in by hand
from the screen, I might not get it all. (I'm no real typist;-)
> show alllocks
exclusive lockmgr ufs (ufs) r = 0 locked @ kern/vfs_subr.c: 3259
exclusive lockmgr nfs (nfs) r = 0 locked @ kern/vfs_lookup.c:737
exclusive sleep mutex kernel area domain (kernel arena domain) r = 0 locked @ kern/subr_vmem.c:1343
exclusive lockmgr bufwait (bufwait) r = 0 locked @ kern/vfs_bio.c:1663
exclusive lockmgr ufs (ufs) r = 0 locked @ kern/vfs_subr.c:2930
exclusive lockmgr syncer (syncer) r = 0 locked @ kern/vfs_subr.c:2474
Process 12 (intr) thread 0x.. (1000008)
exclusive sleep mutex Giant (Giant) r = 0 locked @ kern/kern_intr.c:1152
> ps
- Not going to list them all, but here are the ones that seem interesting...
18 0 0 0 DL vlruwt 0x11d939cc [vnlru]
16 0 0 0 DL (threaded) [bufdaemon]
100069 D qsleep [bufdaemon]
100074 D - [bufspacedaemon-0]
100084 D sdflush 0x11923284 [/ worker]
- and more of these for the other UFS file systems
9 0 0 0 DL psleep 0x1e2f830 [vmdaemon]
8 0 0 0 DL (threaded) [pagedaemon]
100067 D psleep 0x1e2e95c [dom0]
100072 D launds 0x1e2e968 [laundry: dom0]
100073 D umarcl 0x12cc720 [uma]
… a bunch of usb and cam ones
100025 D - 0x1b2ee40 [doneq0]
…
12 0 0 0 RL (threaded) [intr]
100007 I [swi6: task queue]
100008 Run CPU 0 [swi6: Giant taskq]
…
100000 D swapin 0x1d96dfc [swapper]
- and a bunch more in D state.
Does this mean the swapper was trying to swap in?
> acttrace
- just shows the keyboard
kdb_enter() at kdb_enter+0x35/frame
vt_kbdevent() at vt_kdbevent+0x329/frame
kdbmux_intr() at kbdmux_intr+0x19/frame
taskqueue_run_locked() at taskqueue_run_locked+0x175/frame
taskqueue_run() at taskqueue_run+0x44/frame
taskqueue_swi_giant_run(0) at taskqueue_swi_giant_run+0xe/frame
ithread_loop() at ithread_loop+0x237/frame
fork_exit() at fork_exit+0x6c/frame
fork_trampoline() at 0x../frame
> show all vmem
vmem 0x.. 'transient arena'
quantum: 4096
size: 23592960
inuse: 0
free: 23592960
busy tags: 0
free tags: 2
inuse size free size
16777216 0 0 1 23592960
vmem 0x.. 'buffer arena'
quantum: 4096
size: 94683136
inuse: 94502912
free: 180224
busy tags: 1463
free tags: 3
inuse size free size
16384 2 32768 1 16384
32768 39 1277952 1 32768
65536 1422 93192192 0 0
131072 0 0 1 131072
vmem 0x.. 'i386trampoline'
quantum: 1
size: 24576
inuse: 20860
free: 3716
busy tags: 9
free tags: 3
inuse size free size
32 1 48 1 52
64 2 208 0 0
128 2 280 0 0
2048 1 2048 1 3664
4096 2 8192 0 0
8192 1 10084 0 0
vmem 0x.. 'kernel rwx arena'
quantum: 4096
size: 0
inuse: 0
free: 0
busy tags: 0
free tags: 0
vmem 0x.. 'kernel area dom'
quantum: 4096
size: 56623104
inuse: 56582144
free: 40960
busy tags: 11224
free tags: 3
inuse size free size
4096 11091 45428736 0 0
8192 63 516096 0 0
16384 12 196608 0 0
32768 6 196608 0 0
40960 2 81920 1 40960
65536 16 1048576 0 0
94208 1 94208 0 0
110592 1 110592 0 0
131072 15 2441216 0 0
262144 15 3997696 0 0
524288 1 524288 0 0
1048576 1 1945600 0 0
vmem 0x.. 'kernel arena'
quantum: 4096
size: 390070272
inuse: 386613248
free: 3457024
busy tags: 873
free tags: 3
inuse size free size
4096 35 143360 1 4096
8192 2 16384 2 16384
12288 1 12288 0 0
16384 30 491520 0 0
20480 140 2867200 0 0
65536 1 65536 0 0
131072 631 82706432 0 0
1048576 0 0 1 1339392
2097152 27 56623104 1 2097152
8388608 1 13774848 0 0
16777216 3 74883072 0 0
33554432 1 36753408 0 0
67108864 1 118276096 0 0
> alltrace
- I can't face typing too much more, but I'll put a few
here that look interesting
- for csh
sched_switch()
mi_switch()
kern_yield()
getblkx()
breadn_flags()
ffs_update()
ufs_inactive()
VOP_INACTIVE()
vinactivef()
vput_final()
vm_object_deallocate()
vm_map_process_deferred()
kern_munmap()
sys_munmap()
- For cc
sched_switch()
mi_switch()
sleepq_switch()
sleepq_timedwait()
_sleep()
pause_sbt()
vmem_bt_alloc()
keg_alloc_slab()
zone_import()
cache_alloc()
cache_alloc_retry()
uma_zalloc_arg()
bt_fill()
vmem_xalloc()
vmem_alloc()
kmem_alloc()
kmem_malloc_domainset()
page_alloc()
keg_alloc_slab()
zone_import()
cache_alloc()
cache_alloc_retry()
uma_zalloc_arg()
nfscl_nget()
nfs_create()
vop_sigdefer()
nfs_vnodeops_bypass()
VOP_CREATE_APV()
vn_open_cred()
vn_open()
kern_openat()
sys_openat()
Then there are a bunch of these... for cc, make
sched_switch()
mi_switch()
sleepq_switch()
sleepq_catch_signals()
sleepq_wait_sig()
kern_wait6()
sys_wait4()
- for vnlru
sched_switch()
mi_switch()
sleepq_switch()
sleepq_timedwait()
_sleep()
vnlru_proc()
fork_exit()
fork_trampoline()
- for syncer
sched_switch()
mi_switch()
critical_exit_preempt()
intr_event_handle()
intr_execute_handlers()
lapic_handle_intr()
Xapic_isr1()
- interrupt
memset()
cache_alloc()
cache_alloc_retry()
uma_zalloc_arg()
vmem_xalloc()
vmem_bt_alloc()
keg_alloc_slab()
zone_import()
cache_alloc()
cache_alloc_retry()
uma_zalloc_arg()
bt_fill()
vmem_xalloc()
vmem_alloc()
bufkva_alloc()
getnewbuf()
getblkx()
breadn_flags()
ffs_update()
ffs_sync()
sync_fsync()
VOP_FSYNC_APV()
sched_sync()
fork_exit()
fork_trampoline()
- For bufdaemon (a bunch of these)
sched_switch()
mi_switch()
sleepq_switch()
sleepq_timedwait()
_sleep()
buf_daemon()
fork_exit()
fork_trampoline()
vmdaemon and pagedaemon are basically just like above,
sleeping in
vm_daemon()
or
vm_pageout_worker()
or
vm_pageout_laundry_worker()
or
uma_reclaim_worker()
That's all the typing I can take right now.
I can probably make this happen again if you want more specific stuff.
rick
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