zfs deadlock on r360452 relating to busy vm page

Bryan Drewery bdrewery at FreeBSD.org
Tue May 12 22:14:13 UTC 2020


> panic: deadlres_td_sleep_q: possible deadlock detected for 0xfffffe25eefa2e00 (find), blocked for 1802392 ticks

2 stuck processes from procstat -kk before panic
> 72559 101698 tail                -                   mi_switch+0x155 sleepq_switch+0x11a _cv_wait+0x15a rangelock_enter+0x306 zfs_freebsd_getpages+0x14f VOP_GETPAGES_APV+0x59 vnode_pager_getpages+0x37 vm_pager_get_pages+0x4f vm_fault+0x780 vm_fault_trap+0x6e trap_pfault+0x1ee

> 72985 107378 find                -                   mi_switch+0x155 sleepq_switch+0x11a sleeplk+0x106 lockmgr_slock_hard+0x1f5 VOP_LOCK1_APV+0x40 _vn_lock+0x54 lookup+0xdd namei+0x524 vn_open_cred+0x32b kern_openat+0x1fa filemon_wrapper_openat+0x15 amd64_syscall+0x73d


The only find running was thread 107378

I couldn't record much from ddb but got locked vnodes.
> 
> db> show lockedvnods
> Locked vnodes
> vnode 0xfffff804de66e500: type VDIR
>     usecount 3, writecount 0, refcount 2 mountedhere 0
>     flags ()
>     v_object 0xfffff809459cb420 ref 0 pages 0 cleanbuf 0 dirtybuf 0
>     lock type zfs: SHARED (count 1)
> #0 0xffffffff80b94a0f at lockmgr_slock+0xdf
> #1 0xffffffff810e2a40 at VOP_LOCK1_APV+0x40
> #2 0xffffffff80cb14f4 at _vn_lock+0x54
> #3 0xffffffff80c9b3ec at vget_finish+0x6c
> #4 0xffffffff80c8051c at cache_lookup+0x57c
> #5 0xffffffff80c84dad at vfs_cache_lookup+0x7d
> #6 0xffffffff810df996 at VOP_LOOKUP_APV+0x56
> #7 0xffffffff80c8ee61 at lookup+0x601
> #8 0xffffffff80c8e374 at namei+0x524
> #9 0xffffffff80caa83f at kern_statat+0x7f
> #10 0xffffffff80caafff at sys_fstatat+0x2f
> #11 0xffffffff81065c40 at amd64_syscall+0x140
> #12 0xffffffff8103b2a0 at fast_syscall_common+0x101
> vnode 0xfffff808a08f0a00: type VDIR
>     usecount 6, writecount 0, refcount 2 mountedhere 0
>     flags ()
>     v_object 0xfffff801eb930000 ref 0 pages 0 cleanbuf 0 dirtybuf 0
>     lock type zfs: EXCL by thread 0xfffffe24aadb6100 (pid 72267, gmake, tid 104356)
>  with shared waiters pending
> #0 0xffffffff80b94a0f at lockmgr_slock+0xdf
> #1 0xffffffff810e2a40 at VOP_LOCK1_APV+0x40
> #2 0xffffffff80cb14f4 at _vn_lock+0x54
> #3 0xffffffff80c8e93d at lookup+0xdd
> #4 0xffffffff80c8e374 at namei+0x524
> #5 0xffffffff80ca9e69 at kern_funlinkat+0xa9
> #6 0xffffffff80ca9db8 at sys_unlink+0x28
> #7 0xffffffff82780586 at filemon_wrapper_unlink+0x16
> #8 0xffffffff8106623d at amd64_syscall+0x73d
> #9 0xffffffff8103b2a0 at fast_syscall_common+0x101
> 
> vnode 0xfffff80571f29500: type VREG
>     usecount 6, writecount 1, refcount 2
>     flags ()
>     v_object 0xfffff806cb637c60 ref 2 pages 1 cleanbuf 0 dirtybuf 0
>     lock type zfs: SHARED (count 2)
>  with exclusive waiters pending
> #0 0xffffffff80b94a0f at lockmgr_slock+0xdf
> #1 0xffffffff810e2a40 at VOP_LOCK1_APV+0x40
> #2 0xffffffff80cb14f4 at _vn_lock+0x54
> #3 0xffffffff8243af40 at zfs_lookup+0x610
> #4 0xffffffff8243b61e at zfs_freebsd_cachedlookup+0x8e
> #5 0xffffffff810dfb46 at VOP_CACHEDLOOKUP_APV+0x56
> #6 0xffffffff80c84dd8 at vfs_cache_lookup+0xa8
> #7 0xffffffff810df996 at VOP_LOOKUP_APV+0x56
> #8 0xffffffff80c8ee61 at lookup+0x601
> #9 0xffffffff80c8e374 at namei+0x524
> #10 0xffffffff80caa83f at kern_statat+0x7f
> #11 0xffffffff80caafff at sys_fstatat+0x2f
> #12 0xffffffff8106623d at amd64_syscall+0x73d
> #13 0xffffffff8103b2a0 at fast_syscall_common+0x101

It's nice how recent threads are at the top in gdb...
> (kgdb) info threads
>   Id   Target Id                                                 Frame
>   1    Thread 107952 (PID=79390: zfs)                            sched_switch (td=0xfffffe26ebb36000, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
>   2    Thread 102764 (PID=73218: zfs)                            sched_switch (td=0xfffffe2490a12300, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
>   3    Thread 107378 (PID=72985: find)                           sched_switch (td=0xfffffe25eefa2e00, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
>   4    Thread 103940 (PID=72980: rm)                             sched_switch (td=0xfffffe2451932500, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
>   5    Thread 101698 (PID=72559: tail)                           sched_switch (td=0xfffffe255eac0000, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
>   6    Thread 103660 (PID=72280: timestamp)                      sched_switch (td=0xfffffe25f948aa00, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
>   7    Thread 101249 (PID=72280: timestamp/prefix_stdout)        sched_switch (td=0xfffffe264412a100, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
>   8    Thread 101255 (PID=72280: timestamp/prefix_stderr)        sched_switch (td=0xfffffe25c8e9bc00, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
>   9    Thread 104356 (PID=72267: gmake)                          sched_switch (td=0xfffffe24aadb6100, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
>   10   Thread 108476 (PID=66957: vim)                            sched_switch (td=0xfffffe26c8601500, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147

The 2 threads holding shared lock on vnode 0xfffff80571f29500:

The tail thread (101698) is waiting for a zfs rangelock getting pages
for vnode 0xfffff80571f29500

> (kgdb) thread 5
> [Switching to thread 5 (Thread 101698)]
> #0  sched_switch (td=0xfffffe255eac0000, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
> 2147                    cpuid = td->td_oncpu = PCPU_GET(cpuid);
> (kgdb) backtrace
> #0  sched_switch (td=0xfffffe255eac0000, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
> #1  0xffffffff80bce615 in mi_switch (flags=260) at /usr/src/sys/kern/kern_synch.c:542
> #2  0xffffffff80c1cfea in sleepq_switch (wchan=0xfffff810fb57dd48, pri=0) at /usr/src/sys/kern/subr_sleepqueue.c:625
> #3  0xffffffff80b57f0a in _cv_wait (cvp=0xfffff810fb57dd48, lock=0xfffff80049a99040) at /usr/src/sys/kern/kern_condvar.c:146
> #4  0xffffffff82434ab6 in rangelock_enter_reader (rl=0xfffff80049a99018, new=0xfffff8022cadb100) at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_rlock.c:429
> #5  rangelock_enter (rl=0xfffff80049a99018, off=<optimized out>, len=<optimized out>, type=<optimized out>) at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_rlock.c:477
> #6  0xffffffff82443d3f in zfs_getpages (vp=<optimized out>, ma=0xfffffe259f204b18, count=<optimized out>, rbehind=0xfffffe259f204ac4, rahead=0xfffffe259f204ad0) at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c:4500
> #7  zfs_freebsd_getpages (ap=<optimized out>) at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c:4567
> #8  0xffffffff810e3ab9 in VOP_GETPAGES_APV (vop=0xffffffff8250a1e0 <zfs_vnodeops>, a=0xfffffe259f2049f0) at vnode_if.c:2644
> #9  0xffffffff80f349e7 in VOP_GETPAGES (vp=<unavailable>, m=<optimized out>, count=<unavailable>, rbehind=<unavailable>, rahead=<unavailable>) at ./vnode_if.h:1171
> #10 vnode_pager_getpages (object=<optimized out>, m=<optimized out>, count=<unavailable>, rbehind=<unavailable>, rahead=<unavailable>) at /usr/src/sys/vm/vnode_pager.c:743
> #11 0xffffffff80f2a93f in vm_pager_get_pages (object=0xfffff806cb637c60, m=0xfffffe259f204b18, count=1, rbehind=<unavailable>, rahead=<unavailable>) at /usr/src/sys/vm/vm_pager.c:305
> #12 0xffffffff80f054b0 in vm_fault_getpages (fs=<optimized out>, nera=0, behindp=<optimized out>, aheadp=<optimized out>) at /usr/src/sys/vm/vm_fault.c:1163
> #13 vm_fault (map=<optimized out>, vaddr=<optimized out>, fault_type=<optimized out>, fault_flags=<optimized out>, m_hold=<optimized out>) at /usr/src/sys/vm/vm_fault.c:1394
> #14 0xffffffff80f04bde in vm_fault_trap (map=0xfffffe25653949e8, vaddr=<optimized out>, fault_type=<optimized out>, fault_flags=0, signo=0xfffffe259f204d04, ucode=0xfffffe259f204d00) at /usr/src/sys/vm/vm_fault.c:589
> #15 0xffffffff8106544e in trap_pfault (frame=0xfffffe259f204d40, usermode=<optimized out>, signo=<optimized out>, ucode=<unavailable>) at /usr/src/sys/amd64/amd64/trap.c:821
> #16 0xffffffff81064a9c in trap (frame=0xfffffe259f204d40) at /usr/src/sys/amd64/amd64/trap.c:340
> #17 <signal handler called>
> #18 0x00000000002034fc in ?? ()
> (kgdb) frame 11
> #11 0xffffffff80f2a93f in vm_pager_get_pages (object=0xfffff806cb637c60, m=0xfffffe259f204b18, count=1, rbehind=<unavailable>, rahead=<unavailable>) at /usr/src/sys/vm/vm_pager.c:305
> 305             r = (*pagertab[object->type]->pgo_getpages)(object, m, count, rbehind,
> (kgdb) p *object
> $10 = {lock = {lock_object = {lo_name = 0xffffffff8114fa30 "vm object", lo_flags = 627245056, lo_data = 0, lo_witness = 0x0}, rw_lock = 1}, object_list = {tqe_next = 0xfffff806cb637d68, tqe_prev = 0xfffff806cb637b78}, shadow_head = {lh_first = 0x0}, shadow_list = {le_next = 0xffffffffffffffff,
>     le_prev = 0xffffffffffffffff}, memq = {tqh_first = 0xfffffe001cbca850, tqh_last = 0xfffffe001cbca860}, rtree = {rt_root = 18446741875168421969}, size = 1099, domain = {dr_policy = 0x0, dr_iter = 0}, generation = 1, cleangeneration = 1, ref_count = 2, shadow_count = 0, memattr = 6 '\006', type = 2 '\002',
>   flags = 4096, pg_color = 0, paging_in_progress = {__count = 2}, busy = {__count = 0}, resident_page_count = 1, backing_object = 0x0, backing_object_offset = 0, pager_object_list = {tqe_next = 0x0, tqe_prev = 0x0}, rvq = {lh_first = 0x0}, handle = 0xfffff80571f29500, un_pager = {vnp = {vnp_size = 4499568,
>       writemappings = 0}, devp = {devp_pglist = {tqh_first = 0x44a870, tqh_last = 0x0}, ops = 0x0, dev = 0x0}, sgp = {sgp_pglist = {tqh_first = 0x44a870, tqh_last = 0x0}}, swp = {swp_tmpfs = 0x44a870, swp_blks = {pt_root = 0}, writemappings = 0}}, cred = 0x0, charge = 0, umtx_data = 0x0}
> (kgdb) p object->handle
> $11 = (void *) 0xfffff80571f29500

> (kgdb) p *(struct vnode *) 0xfffff80571f29500
> $18 = {v_type = VREG, v_irflag = 0, v_op = 0xffffffff8250a1e0 <zfs_vnodeops>, v_data = 0xfffff80049a99000, v_mount = 0xfffffe247e5f3700, v_nmntvnodes = {tqe_next = 0xfffff8086eb38a00, tqe_prev = 0xfffff80461c2d7a0}, {v_mountedhere = 0x0, v_unpcb = 0x0, v_rdev = 0x0, v_fifoinfo = 0x0}, v_hashlist = {le_next = 0x0,
>     le_prev = 0x0}, v_cache_src = {lh_first = 0x0}, v_cache_dst = {tqh_first = 0x0, tqh_last = 0xfffff80571f29550}, v_cache_dd = 0x0, v_lock = {lock_object = {lo_name = 0xffffffff82486a37 "zfs", lo_flags = 117112832, lo_data = 0, lo_witness = 0x0}, lk_lock = 37, lk_exslpfail = 0, lk_timo = 51, lk_pri = 96,
>     lk_stack = {depth = 14, pcs = {18446744071574211087, 18446744071579773504, 18446744071575377140, 18446744071600058176, 18446744071600059934, 18446744071579761478, 18446744071575195096, 18446744071579761046, 18446744071575236193, 18446744071575233396, 18446744071575349311, 18446744071575351295,
>         18446744071579263549, 18446744071579087520, 0, 0, 0, 0}}}, v_interlock = {lock_object = {lo_name = 0xffffffff8123c142 "vnode interlock", lo_flags = 16973824, lo_data = 0, lo_witness = 0xfffff8123fd73600}, mtx_lock = 0}, v_vnlock = 0xfffff80571f29568, v_vnodelist = {tqe_next = 0xfffff8064bd0dc80,
>     tqe_prev = 0xfffff80e250788d8}, v_lazylist = {tqe_next = 0x0, tqe_prev = 0x0}, v_bufobj = {bo_lock = {lock_object = {lo_name = 0xffffffff811fb7ab "bufobj interlock", lo_flags = 86179840, lo_data = 0, lo_witness = 0xfffff8123fd7dd80}, rw_lock = 1}, bo_ops = 0xffffffff8191ead0 <buf_ops_bio>,
>     bo_object = 0xfffff806cb637c60, bo_synclist = {le_next = 0x0, le_prev = 0x0}, bo_private = 0xfffff80571f29500, bo_clean = {bv_hd = {tqh_first = 0x0, tqh_last = 0xfffff80571f296c0}, bv_root = {pt_root = 0}, bv_cnt = 0}, bo_dirty = {bv_hd = {tqh_first = 0x0, tqh_last = 0xfffff80571f296e0}, bv_root = {pt_root = 0},
>       bv_cnt = 0}, bo_numoutput = 0, bo_flag = 0, bo_domain = 5, bo_bsize = 131072}, v_pollinfo = 0x0, v_label = 0x0, v_lockf = 0x0, v_rl = {rl_waiters = {tqh_first = 0xfffff80f2cc12708, tqh_last = 0xfffff80f2cc12708}, rl_currdep = 0x0}, v_cstart = 0, v_lasta = 0, v_lastw = 0, v_clen = 0, v_holdcnt = 2,
>   v_usecount = 6, v_iflag = 0, v_vflag = 0, v_mflag = 0, v_dbatchcpu = -1, v_writecount = 1, v_hash = 45676874}

Is that thread busying the vm object?


thread 101255 (timestamp/prefix_stderr) which is also acting on vnode
0xfffff80571f29500 that the tail thread 101698 was.

> (kgdb) thread
> [Current thread is 8 (Thread 101255)]
> (kgdb) backtrace
> #0  sched_switch (td=0xfffffe25c8e9bc00, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
> #1  0xffffffff80bce615 in mi_switch (flags=260) at /usr/src/sys/kern/kern_synch.c:542
> #2  0xffffffff80c1cfea in sleepq_switch (wchan=0xfffffe001cbca850, pri=84) at /usr/src/sys/kern/subr_sleepqueue.c:625
> #3  0xffffffff80f1de50 in _vm_page_busy_sleep (obj=<optimized out>, m=0xfffffe001cbca850, pindex=<optimized out>, wmesg=<optimized out>, allocflags=21504, locked=false) at /usr/src/sys/vm/vm_page.c:1094
> #4  0xffffffff80f241f7 in vm_page_grab_sleep (object=0xfffff806cb637c60, m=<optimized out>, pindex=<optimized out>, wmesg=<optimized out>, allocflags=21504, locked=<error reading variable: Cannot access memory at address 0x0>) at /usr/src/sys/vm/vm_page.c:4326
> #5  vm_page_acquire_unlocked (object=0xfffff806cb637c60, pindex=1098, prev=<optimized out>, mp=0xfffffe2717fc6730, allocflags=21504) at /usr/src/sys/vm/vm_page.c:4469
> #6  0xffffffff80f24c61 in vm_page_grab_valid_unlocked (mp=0xfffffe2717fc6730, object=0xfffff806cb637c60, pindex=1098, allocflags=21504) at /usr/src/sys/vm/vm_page.c:4645
> #7  0xffffffff82440246 in page_busy (vp=0xfffff80571f29500, start=4497408, off=<optimized out>, nbytes=<optimized out>) at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c:414
> #8  update_pages (vp=0xfffff80571f29500, start=4497408, len=32, os=0xfffff8096a277400, oid=2209520, segflg=<optimized out>, tx=<optimized out>) at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c:482
> #9  zfs_write (vp=<optimized out>, uio=<optimized out>, ioflag=0, cr=<optimized out>, ct=<optimized out>) at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c:1071
> #10 zfs_freebsd_write (ap=<optimized out>) at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c:4838
> #11 0xffffffff810e0eaf in VOP_WRITE_APV (vop=0xffffffff8250a1e0 <zfs_vnodeops>, a=0xfffffe2717fc68c8) at vnode_if.c:925
> #12 0xffffffff80cb574c in VOP_WRITE (vp=0xfffff80571f29500, uio=0xfffffe2717fc6bb0, ioflag=8323073, cred=<optimized out>) at ./vnode_if.h:413
> #13 vn_write (fp=0xfffff8048195e8c0, uio=<optimized out>, active_cred=<optimized out>, flags=<optimized out>, td=<optimized out>) at /usr/src/sys/kern/vfs_vnops.c:894
> #14 0xffffffff80cb50c3 in vn_io_fault_doio (args=0xfffffe2717fc6af0, uio=0xfffffe2717fc6bb0, td=0xfffffe25c8e9bc00) at /usr/src/sys/kern/vfs_vnops.c:959
> #15 0xffffffff80cb1c8c in vn_io_fault1 (vp=<optimized out>, uio=0xfffffe2717fc6bb0, args=0xfffffe2717fc6af0, td=0xfffffe25c8e9bc00) at /usr/src/sys/kern/vfs_vnops.c:1077
> #16 0xffffffff80cafa32 in vn_io_fault (fp=0xfffff8048195e8c0, uio=0xfffffe2717fc6bb0, active_cred=0xfffff80f2cc12708, flags=0, td=<optimized out>) at /usr/src/sys/kern/vfs_vnops.c:1181
> #17 0xffffffff80c34331 in fo_write (fp=0xfffff8048195e8c0, uio=0xfffffe2717fc6bb0, active_cred=<unavailable>, flags=<unavailable>, td=0xfffffe25c8e9bc00) at /usr/src/sys/sys/file.h:326
> #18 dofilewrite (td=0xfffffe25c8e9bc00, fd=2, fp=0xfffff8048195e8c0, auio=0xfffffe2717fc6bb0, offset=<optimized out>, flags=<optimized out>) at /usr/src/sys/kern/sys_generic.c:564
> #19 0xffffffff80c33eb0 in kern_writev (td=0xfffffe25c8e9bc00, fd=2, auio=<optimized out>) at /usr/src/sys/kern/sys_generic.c:491
> #20 sys_write (td=0xfffffe25c8e9bc00, uap=<optimized out>) at /usr/src/sys/kern/sys_generic.c:406
> #21 0xffffffff8106623d in syscallenter (td=<optimized out>) at /usr/src/sys/amd64/amd64/../../kern/subr_syscall.c:150
> #22 amd64_syscall (td=0xfffffe25c8e9bc00, traced=0) at /usr/src/sys/amd64/amd64/trap.c:1161
> #23 <signal handler called>
> #24 0x000000080043d53a in ?? ()

Maybe r358443 is related?


> (kgdb) frame 4
> #4  0xffffffff80f241f7 in vm_page_grab_sleep (object=0xfffff806cb637c60, m=<optimized out>, pindex=<optimized out>, wmesg=<optimized out>, allocflags=21504, locked=<error reading variable: Cannot access memory at address 0x0>) at /usr/src/sys/vm/vm_page.c:4326
> 4326            if (_vm_page_busy_sleep(object, m, m->pindex, wmesg, allocflags,
> (kgdb) p *object
> $8 = {lock = {lock_object = {lo_name = 0xffffffff8114fa30 "vm object", lo_flags = 627245056, lo_data = 0, lo_witness = 0x0}, rw_lock = 1}, object_list = {tqe_next = 0xfffff806cb637d68, tqe_prev = 0xfffff806cb637b78}, shadow_head = {lh_first = 0x0}, shadow_list = {le_next = 0xffffffffffffffff,
>     le_prev = 0xffffffffffffffff}, memq = {tqh_first = 0xfffffe001cbca850, tqh_last = 0xfffffe001cbca860}, rtree = {rt_root = 18446741875168421969}, size = 1099, domain = {dr_policy = 0x0, dr_iter = 0}, generation = 1, cleangeneration = 1, ref_count = 2, shadow_count = 0, memattr = 6 '\006', type = 2 '\002',
>   flags = 4096, pg_color = 0, paging_in_progress = {__count = 2}, busy = {__count = 0}, resident_page_count = 1, backing_object = 0x0, backing_object_offset = 0, pager_object_list = {tqe_next = 0x0, tqe_prev = 0x0}, rvq = {lh_first = 0x0}, handle = 0xfffff80571f29500, un_pager = {vnp = {vnp_size = 4499568,
>       writemappings = 0}, devp = {devp_pglist = {tqh_first = 0x44a870, tqh_last = 0x0}, ops = 0x0, dev = 0x0}, sgp = {sgp_pglist = {tqh_first = 0x44a870, tqh_last = 0x0}}, swp = {swp_tmpfs = 0x44a870, swp_blks = {pt_root = 0}, writemappings = 0}}, cred = 0x0, charge = 0, umtx_data = 0x0}
> (kgdb) frame 5
> #5  vm_page_acquire_unlocked (object=0xfffff806cb637c60, pindex=1098, prev=<optimized out>, mp=0xfffffe2717fc6730, allocflags=21504) at /usr/src/sys/vm/vm_page.c:4469
> 4469                    if (!vm_page_grab_sleep(object, m, pindex, "pgnslp",
> (kgdb) p *m
> $9 = {plinks = {q = {tqe_next = 0xffffffffffffffff, tqe_prev = 0xffffffffffffffff}, s = {ss = {sle_next = 0xffffffffffffffff}}, memguard = {p = 18446744073709551615, v = 18446744073709551615}, uma = {slab = 0xffffffffffffffff, zone = 0xffffffffffffffff}}, listq = {tqe_next = 0x0, tqe_prev = 0xfffff806cb637ca8},
>   object = 0xfffff806cb637c60, pindex = 1098, phys_addr = 18988408832, md = {pv_list = {tqh_first = 0x0, tqh_last = 0xfffffe001cbca888}, pv_gen = 44682, pat_mode = 6}, ref_count = 2147483648, busy_lock = 1588330502, a = {{flags = 0, queue = 255 '\377', act_count = 0 '\000'}, _bits = 16711680}, order = 13 '\r',
>   pool = 0 '\000', flags = 1 '\001', oflags = 0 '\000', psind = 0 '\000', segind = 6 '\006', valid = 0 '\000', dirty = 0 '\000'}

Pretty sure this thread is holding the rangelock from zfs_write() that
tail is waiting on. So what is this thread (101255) waiting on exactly
for? I'm not sure the way to track down what is using vm object
0xfffff806cb637c60. If the tail thread busied the page then they are
waiting on each other I guess. If that's true then r358443 removing the
write lock on the object in update_pages() could be a problem.


Not sure the rest is interesting. I think they are just waiting on the
locked vnode but I give it here in case I missed something.

thread 101249 (timestamp/prefix_stdout) is also acting on vnode
0xfffff80571f29500

> (kgdb) thread 7
> [Switching to thread 7 (Thread 101249)]
> #0  sched_switch (td=0xfffffe264412a100, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
> 2147                    cpuid = td->td_oncpu = PCPU_GET(cpuid);
> (kgdb) backtrace
> #0  sched_switch (td=0xfffffe264412a100, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
> #1  0xffffffff80bce615 in mi_switch (flags=260) at /usr/src/sys/kern/kern_synch.c:542
> #2  0xffffffff80c1cfea in sleepq_switch (wchan=0xfffff8048195e8e2, pri=119) at /usr/src/sys/kern/subr_sleepqueue.c:625
> #3  0xffffffff80bcdb6d in _sleep (ident=0xfffff8048195e8e2, lock=<optimized out>, priority=119, wmesg=0xffffffff8123c694 "vofflock", sbt=<optimized out>, pr=0, flags=256) at /usr/src/sys/kern/kern_synch.c:221
> #4  0xffffffff80cb203a in foffset_lock (fp=0xfffff8048195e8c0, flags=<optimized out>) at /usr/src/sys/kern/vfs_vnops.c:700
> #5  0xffffffff80caf909 in foffset_lock_uio (fp=<optimized out>, uio=<optimized out>, flags=<optimized out>) at /usr/src/sys/kern/vfs_vnops.c:748
> #6  vn_io_fault (fp=0xfffff8048195e8c0, uio=0xfffffe2719d9cbb0, active_cred=0xfffff80786ecad00, flags=0, td=0xfffffe264412a100) at /usr/src/sys/kern/vfs_vnops.c:1163
> #7  0xffffffff80c34331 in fo_write (fp=0xfffff8048195e8c0, uio=0xfffffe2719d9cbb0, active_cred=<unavailable>, flags=<unavailable>, td=0xfffffe264412a100) at /usr/src/sys/sys/file.h:326
> #8  dofilewrite (td=0xfffffe264412a100, fd=1, fp=0xfffff8048195e8c0, auio=0xfffffe2719d9cbb0, offset=<optimized out>, flags=<optimized out>) at /usr/src/sys/kern/sys_generic.c:564
> #9  0xffffffff80c33eb0 in kern_writev (td=0xfffffe264412a100, fd=1, auio=<optimized out>) at /usr/src/sys/kern/sys_generic.c:491
> #10 sys_write (td=0xfffffe264412a100, uap=<optimized out>) at /usr/src/sys/kern/sys_generic.c:406
> #11 0xffffffff8106623d in syscallenter (td=<optimized out>) at /usr/src/sys/amd64/amd64/../../kern/subr_syscall.c:150
> #12 amd64_syscall (td=0xfffffe264412a100, traced=0) at /usr/src/sys/amd64/amd64/trap.c:1161
> #13 <signal handler called>
> #14 0x000000080043d53a in ?? ()
> Backtrace stopped: Cannot access memory at address 0x7fffdfffddd8
> (kgdb) frame 6
> #6  vn_io_fault (fp=0xfffff8048195e8c0, uio=0xfffffe2719d9cbb0, active_cred=0xfffff80786ecad00, flags=0, td=0xfffffe264412a100) at /usr/src/sys/kern/vfs_vnops.c:1163
> 1163            foffset_lock_uio(fp, uio, flags);
> (kgdb) p *fp
> $22 = {f_data = 0xfffff80571f29500, f_ops = 0xffffffff81923a10 <vnops>, f_cred = 0xfffff80786ecad00, f_vnode = 0xfffff80571f29500, f_type = 1, f_vnread_flags = 3, f_flag = 2, f_count = 4, {f_seqcount = 127, f_pipegen = 127}, f_nextoff = 4499536, f_vnun = {fvn_cdevpriv = 0x0, fvn_advice = 0x0}, f_offset = 4499536,
>   f_label = 0x0}

thread 104356 (gmake) is just waiting on the lock for vnode
0xfffff80571f29500
It also is holding exclusive lock on directory vnode 0xfffff808a08f0a00

> (kgdb) thread 9
> [Switching to thread 9 (Thread 104356)]
> #0  sched_switch (td=0xfffffe24aadb6100, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
> 2147                    cpuid = td->td_oncpu = PCPU_GET(cpuid);
> (kgdb) backtrace
> #0  sched_switch (td=0xfffffe24aadb6100, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
> #1  0xffffffff80bce615 in mi_switch (flags=260) at /usr/src/sys/kern/kern_synch.c:542
> #2  0xffffffff80c1cfea in sleepq_switch (wchan=0xfffff80571f29568, pri=96) at /usr/src/sys/kern/subr_sleepqueue.c:625
> #3  0xffffffff80b954f6 in sleeplk (lk=0xfffff80571f29568, flags=532480, ilk=<optimized out>, wmesg=<optimized out>, pri=<optimized out>, timo=51, queue=0) at /usr/src/sys/kern/kern_lock.c:295
> #4  0xffffffff80b93a1e in lockmgr_xlock_hard (lk=0xfffff80571f29568, flags=<unavailable>, ilk=0x0, file=<optimized out>, line=1432, lwa=0xfffff80571f29568) at /usr/src/sys/kern/kern_lock.c:841
> #5  0xffffffff810e2a40 in VOP_LOCK1_APV (vop=0xffffffff8250a1e0 <zfs_vnodeops>, a=0xfffffe271833f4d8) at vnode_if.c:1989
> #6  0xffffffff80cb14f4 in VOP_LOCK1 (vp=0xfffff80571f29500, flags=532480, file=0xffffffff82472ac9 "/usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c", line=1432) at ./vnode_if.h:879
> #7  _vn_lock (vp=0xfffff80571f29500, flags=532480, file=0xffffffff82472ac9 "/usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c", line=1432) at /usr/src/sys/kern/vfs_vnops.c:1613
> #8  0xffffffff8243af40 in zfs_lookup_lock (dvp=0xfffff808a08f0a00, vp=0xfffff80571f29500, name=0xfffffe271833f630 "copool-basic.sh.log", lkflags=532480) at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c:1432
> #9  zfs_lookup (dvp=0xfffff808a08f0a00, nm=0xfffffe271833f630 "copool-basic.sh.log", vpp=<optimized out>, cnp=0xfffffe271833faf0, nameiop=2, cr=<optimized out>, td=<optimized out>, flags=0, cached=1) at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c:1606
> #10 0xffffffff8243b61e in zfs_freebsd_lookup (ap=0xfffffe271833f780, cached=<error reading variable: Cannot access memory at address 0x1>) at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c:4900
> #11 zfs_freebsd_cachedlookup (ap=0xfffffe271833f780) at /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c:4908
> #12 0xffffffff810dfb46 in VOP_CACHEDLOOKUP_APV (vop=0xffffffff8250a1e0 <zfs_vnodeops>, a=0xfffffe271833f780) at vnode_if.c:180
> #13 0xffffffff80c84dd8 in VOP_CACHEDLOOKUP (dvp=0xfffff808a08f0a00, vpp=0xfffffe271833fac0, cnp=0xfffffe271833faf0) at ./vnode_if.h:80
> #14 vfs_cache_lookup (ap=<optimized out>) at /usr/src/sys/kern/vfs_cache.c:2149
> #15 0xffffffff810df996 in VOP_LOOKUP_APV (vop=0xffffffff8250a1e0 <zfs_vnodeops>, a=0xfffffe271833f820) at vnode_if.c:117
> #16 0xffffffff80c8ee61 in VOP_LOOKUP (dvp=0xfffff808a08f0a00, vpp=0xfffffe271833fac0, cnp=0xfffffe271833faf0) at ./vnode_if.h:54
> #17 lookup (ndp=0xfffffe271833fa60) at /usr/src/sys/kern/vfs_lookup.c:951
> #18 0xffffffff80c8e374 in namei (ndp=0xfffffe271833fa60) at /usr/src/sys/kern/vfs_lookup.c:512
> #19 0xffffffff80ca9e69 in kern_funlinkat (td=0xfffffe24aadb6100, dfd=-100, path=0x800a3982e <error: Cannot access memory at address 0x800a3982e>, fd=<optimized out>, pathseg=UIO_USERSPACE, flag=<optimized out>, oldinum=0) at /usr/src/sys/kern/vfs_syscalls.c:1819
> #20 0xffffffff80ca9db8 in sys_unlink (td=<unavailable>, uap=<optimized out>) at /usr/src/sys/kern/vfs_syscalls.c:1747
> #21 0xffffffff82780586 in filemon_wrapper_unlink (td=<unavailable>, uap=0xfffffe24aadb64d8) at /usr/src/sys/dev/filemon/filemon_wrapper.c:350
> #22 0xffffffff8106623d in syscallenter (td=<optimized out>) at /usr/src/sys/amd64/amd64/../../kern/subr_syscall.c:150
> #23 amd64_syscall (td=0xfffffe24aadb6100, traced=0) at /usr/src/sys/amd64/amd64/trap.c:1161

thread 108476 (vim) is waiting to lock the directory vnode
0xfffff808a08f0a00

> (kgdb) thread 10
> [Switching to thread 10 (Thread 108476)]
> #0  sched_switch (td=0xfffffe26c8601500, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
> 2147                    cpuid = td->td_oncpu = PCPU_GET(cpuid);
> (kgdb) backtrace
> #0  sched_switch (td=0xfffffe26c8601500, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
> #1  0xffffffff80bce615 in mi_switch (flags=260) at /usr/src/sys/kern/kern_synch.c:542
> #2  0xffffffff80c1cfea in sleepq_switch (wchan=0xfffff808a08f0a68, pri=96) at /usr/src/sys/kern/subr_sleepqueue.c:625
> #3  0xffffffff80b954f6 in sleeplk (lk=0xfffff808a08f0a68, flags=2105344, ilk=<optimized out>, wmesg=<optimized out>, pri=<optimized out>, timo=51, queue=1) at /usr/src/sys/kern/kern_lock.c:295
> #4  0xffffffff80b93525 in lockmgr_slock_hard (lk=0xfffff808a08f0a68, flags=2105344, ilk=<optimized out>, file=0xffffffff811fb967 "/usr/src/sys/kern/vfs_subr.c", line=2930, lwa=<optimized out>) at /usr/src/sys/kern/kern_lock.c:649
> #5  0xffffffff810e2a40 in VOP_LOCK1_APV (vop=0xffffffff8250a1e0 <zfs_vnodeops>, a=0xfffffe271d46d6b8) at vnode_if.c:1989
> #6  0xffffffff80cb14f4 in VOP_LOCK1 (vp=0xfffff808a08f0a00, flags=2105344, file=0xffffffff811fb967 "/usr/src/sys/kern/vfs_subr.c", line=2930) at ./vnode_if.h:879
> #7  _vn_lock (vp=0xfffff808a08f0a00, flags=2105344, file=0xffffffff811fb967 "/usr/src/sys/kern/vfs_subr.c", line=2930) at /usr/src/sys/kern/vfs_vnops.c:1613
> #8  0xffffffff80c9b3ec in vget_finish (vp=0xfffff808a08f0a00, flags=2105344, vs=VGET_USECOUNT) at /usr/src/sys/kern/vfs_subr.c:2930
> #9  0xffffffff80c8051c in cache_lookup (dvp=<optimized out>, vpp=<optimized out>, cnp=<optimized out>, tsp=<optimized out>, ticksp=<optimized out>) at /usr/src/sys/kern/vfs_cache.c:1407
> #10 0xffffffff80c84dad in vfs_cache_lookup (ap=<optimized out>) at /usr/src/sys/kern/vfs_cache.c:2147
> #11 0xffffffff810df996 in VOP_LOOKUP_APV (vop=0xffffffff8250a1e0 <zfs_vnodeops>, a=0xfffffe271d46d8a0) at vnode_if.c:117
> #12 0xffffffff80c8ee61 in VOP_LOOKUP (dvp=0xfffff804de66e500, vpp=0xfffffe271d46da60, cnp=0xfffffe271d46da90) at ./vnode_if.h:54
> #13 lookup (ndp=0xfffffe271d46da00) at /usr/src/sys/kern/vfs_lookup.c:951
> #14 0xffffffff80c8e374 in namei (ndp=0xfffffe271d46da00) at /usr/src/sys/kern/vfs_lookup.c:512
> #15 0xffffffff80caa83f in kern_statat (td=0xfffffe26c8601500, flag=<optimized out>, fd=<optimized out>, path=0x8049d12c0 <error: Cannot access memory at address 0x8049d12c0>, pathseg=UIO_USERSPACE, sbp=0xfffffe271d46db28, hook=0x0) at /usr/src/sys/kern/vfs_syscalls.c:2340
> #16 0xffffffff80caafff in sys_fstatat (td=<unavailable>, uap=0xfffffe26c86018d8) at /usr/src/sys/kern/vfs_syscalls.c:2317
> #17 0xffffffff81065c40 in syscallenter (td=<optimized out>) at /usr/src/sys/amd64/amd64/../../kern/subr_syscall.c:162
> #18 amd64_syscall (td=0xfffffe26c8601500, traced=0) at /usr/src/sys/amd64/amd64/trap.c:1161
> #19 <signal handler called>
> #20 0x00000008020ba75a in ?? ()

Lastly the find thread (107378) is waiting to lock the same directory
vnode 0xfffff808a08f0a00

> (kgdb) thread 3
> [Switching to thread 3 (Thread 107378)]
> #0  sched_switch (td=0xfffffe25eefa2e00, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
> 2147                    cpuid = td->td_oncpu = PCPU_GET(cpuid);
> (kgdb) backtrace
> #0  sched_switch (td=0xfffffe25eefa2e00, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2147
> #1  0xffffffff80bce615 in mi_switch (flags=260) at /usr/src/sys/kern/kern_synch.c:542
> #2  0xffffffff80c1cfea in sleepq_switch (wchan=0xfffff808a08f0a68, pri=96) at /usr/src/sys/kern/subr_sleepqueue.c:625
> #3  0xffffffff80b954f6 in sleeplk (lk=0xfffff808a08f0a68, flags=2106368, ilk=<optimized out>, wmesg=<optimized out>, pri=<optimized out>, timo=51, queue=1) at /usr/src/sys/kern/kern_lock.c:295
> #4  0xffffffff80b93525 in lockmgr_slock_hard (lk=0xfffff808a08f0a68, flags=2106368, ilk=<optimized out>, file=0xffffffff811f0ff4 "/usr/src/sys/kern/vfs_lookup.c", line=737, lwa=<optimized out>) at /usr/src/sys/kern/kern_lock.c:649
> #5  0xffffffff810e2a40 in VOP_LOCK1_APV (vop=0xffffffff8250a1e0 <zfs_vnodeops>, a=0xfffffe271bee5748) at vnode_if.c:1989
> #6  0xffffffff80cb14f4 in VOP_LOCK1 (vp=0xfffff808a08f0a00, flags=2106368, file=0xffffffff811f0ff4 "/usr/src/sys/kern/vfs_lookup.c", line=737) at ./vnode_if.h:879
> #7  _vn_lock (vp=0xfffff808a08f0a00, flags=2106368, file=0xffffffff811f0ff4 "/usr/src/sys/kern/vfs_lookup.c", line=737) at /usr/src/sys/kern/vfs_vnops.c:1613
> #8  0xffffffff80c8e93d in lookup (ndp=0xfffffe271bee5a88) at /usr/src/sys/kern/vfs_lookup.c:735
> #9  0xffffffff80c8e374 in namei (ndp=0xfffffe271bee5a88) at /usr/src/sys/kern/vfs_lookup.c:512
> #10 0xffffffff80cb0bdb in vn_open_cred (ndp=0xfffffe271bee5a88, flagp=0xfffffe271bee5bb4, cmode=0, vn_open_flags=0, cred=0xfffff80786ecad00, fp=0xfffff802a8627690) at /usr/src/sys/kern/vfs_vnops.c:288
> #11 0xffffffff80ca8a8a in kern_openat (td=0xfffffe25eefa2e00, fd=<optimized out>, path=<optimized out>, pathseg=<optimized out>, flags=1048577, mode=<optimized out>) at /usr/src/sys/kern/vfs_syscalls.c:1083
> #12 0xffffffff82780415 in filemon_wrapper_openat (td=0xfffffe25eefa2e00, uap=0xfffffe25eefa31d8) at /usr/src/sys/dev/filemon/filemon_wrapper.c:232
> #13 0xffffffff8106623d in syscallenter (td=<optimized out>) at /usr/src/sys/amd64/amd64/../../kern/subr_syscall.c:150
> #14 amd64_syscall (td=0xfffffe25eefa2e00, traced=0) at /usr/src/sys/amd64/amd64/trap.c:1161


-- 
Regards,
Bryan Drewery

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