I have this with kernel 4.4.19-2-default
2016-09-12T02:16:30.441450+02:00 zappa automount[32694]: st_expire: state 1
path /nfstest
2016-09-12T02:16:30.441749+02:00 zappa automount[32694]: expire_proc: exp_proc
= 140406785332992 path /nfstest
2016-09-12T02:16:30.443177+02:00 zappa automount[32694]: expire_proc_indirect:
expire /nfstest/glaukos_home_data
2016-09-12T02:16:30.444309+02:00 zappa kernel: [1169842.213096] BUG: sleeping
function called from invalid context at ../fs/dcache.c:760
2016-09-12T02:16:30.444317+02:00 zappa kernel: [1169842.213102] in_atomic(): 1,
irqs_disabled(): 0, pid: 19278, name: automount
2016-09-12T02:16:30.444318+02:00 zappa kernel: [1169842.213104] CPU: 0 PID:
19278 Comm: automount Tainted: G W O 4.4.19-2-default #1
2016-09-12T02:16:30.444318+02:00 zappa kernel: [1169842.213106] Hardware name:
FUJITSU D3402-B1/D3402-B1, BIOS V5.0.0.11 R1.15.0 for D3402-B1x
06/28/2016
2016-09-12T02:16:30.444319+02:00 zappa kernel: [1169842.213109]
0000000000000000 ffffffff81327f68 ffff88052a305198 ffff88080aba4b60
2016-09-12T02:16:30.444319+02:00 zappa kernel: [1169842.213110]
ffffffff8121c1ea ffff88059cbabd50 ffff88080aba4b60 ffff8807feed0520
2016-09-12T02:16:30.444319+02:00 zappa kernel: [1169842.213112]
0000000000000000 ffffffff8120f262 ffff88052a305198 ffff88052a305198
2016-09-12T02:16:30.444320+02:00 zappa kernel: [1169842.213114] Call Trace:
2016-09-12T02:16:30.444320+02:00 zappa kernel: [1169842.213127]
[<ffffffff81019ed9>] dump_trace+0x59/0x320
2016-09-12T02:16:30.444320+02:00 zappa kernel: [1169842.213131]
[<ffffffff8101a29a>] show_stack_log_lvl+0xfa/0x180
2016-09-12T02:16:30.444321+02:00 zappa kernel: [1169842.213133]
[<ffffffff8101b051>] show_stack+0x21/0x40
2016-09-12T02:16:30.444321+02:00 zappa kernel: [1169842.213135]
[<ffffffff81327f68>] dump_stack+0x5c/0x84
2016-09-12T02:16:30.444321+02:00 zappa kernel: [1169842.213137]
[<ffffffff8121c1ea>] dput+0x2a/0x250
2016-09-12T02:16:30.444322+02:00 zappa kernel: [1169842.213141]
[<ffffffff8120f262>] follow_down_one+0x22/0x50
2016-09-12T02:16:30.444322+02:00 zappa kernel: [1169842.213147]
[<ffffffffa0164ec4>] autofs4_mount_busy+0x34/0x110 [autofs4]
2016-09-12T02:16:30.444322+02:00 zappa kernel: [1169842.213154]
[<ffffffffa016527e>] should_expire+0x4e/0x3c0 [autofs4]
2016-09-12T02:16:30.444323+02:00 zappa kernel: [1169842.213157]
[<ffffffffa01658dc>] autofs4_expire_indirect+0x1bc/0x390 [autofs4]
2016-09-12T02:16:30.444323+02:00 zappa kernel: [1169842.213159]
[<ffffffffa0165dc2>] autofs4_do_expire_multi+0x92/0xa0 [autofs4]
2016-09-12T02:16:30.444323+02:00 zappa kernel: [1169842.213162]
[<ffffffffa0166780>] _autofs_dev_ioctl+0x2a0/0x340 [autofs4]
2016-09-12T02:16:30.444324+02:00 zappa kernel: [1169842.213165]
[<ffffffffa016682f>] autofs_dev_ioctl+0xf/0x20 [autofs4]
2016-09-12T02:16:30.444324+02:00 zappa kernel: [1169842.213167]
[<ffffffff812184fc>] do_vfs_ioctl+0x30c/0x570
2016-09-12T02:16:30.444324+02:00 zappa kernel: [1169842.213172]
[<ffffffff812187d4>] SyS_ioctl+0x74/0x80
2016-09-12T02:16:30.444324+02:00 zappa kernel: [1169842.213176]
[<ffffffff8160a476>] entry_SYSCALL_64_fastpath+0x16/0x75
2016-09-12T02:16:30.445510+02:00 zappa automount[32694]: 1 remaining in
/nfstest
2016-09-12T02:16:30.445681+02:00 zappa automount[32694]: expire_cleanup: got
thid 140406785332992 path /nfstest stat 3
2016-09-12T02:16:30.445781+02:00 zappa automount[32694]: expire_cleanup:
sigchld: exp 140406785332992 finished, switching from 2 to 1
2016-09-12T02:16:30.445888+02:00 zappa automount[32694]: st_ready: st_ready():
state = 2 path /nfstest
2016-09-12T02:16:30.448298+02:00 zappa kernel: [1169842.214070] DWARF2 unwinder
stuck at entry_SYSCALL_64_fastpath+0x16/0x75
2016-09-12T02:16:30.448304+02:00 zappa kernel: [1169842.214071]
2016-09-12T02:16:30.448305+02:00 zappa kernel: [1169842.214072] Leftover
inexact backtrace:
2016-09-12T02:16:30.448305+02:00 zappa kernel: [1169842.214072]
2016-09-12T02:17:17.376311+02:00 zappa kernel: [1169889.140842] nfs: server
skylla.ga.local not responding, timed out
2016-09-12T02:18:53.504315+02:00 zappa kernel: [1169985.266179] nfs: server
skylla.ga.local not responding, timed out
Looks like
4.8-rc4 spews "BUG: sleeping function called from invalid context at
fs/dcache.c:757"
http://www.spinics.net/lists/kernel/msg2330865.html