Samba/CIFS Linux server hangs when a client tries to write to its shares (Doc ID 2412089.1)

Last updated on MAY 14, 2020

Applies to:

Symptoms

An Oracle Linux 7.4  CIFS/Samba server, running as a virtual guest on OVM has the samba service intermittently hang when a client system tries to write to the samba shares.

Oswatcher output shows 100% disk utilization on the virtual disks being used for the samba shares:

zzz ***Thu May 31 08:59:58 NZST 2018
avg-cpu: %user %nice %system %iowait %steal %idle
19.70 0.00 12.42 0.00 0.10 67.78

Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
xvda 0.00 0.00 0.00 1.00 0.00 4.00 8.00 0.00 0.00 0.00 0.00 0.00 0.00
xvdb 0.00 4.00 0.00 31.00 0.00 102.00 6.58 0.01 0.32 0.00 0.32 0.32 1.00
xvdc 0.00 0.00 0.00 0.00 0.00 0.00 0.00 3.00 0.00 0.00 0.00 0.00 100.00 <---------------100% utilization
xvdd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
xvde 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
xvdf 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
xvdg 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
xvdh 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
xvdi 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.00 0.00 0.00 0.00 0.00 100.00 <---------------100% utilization
dm-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-2 0.00 0.00 0.00 27.00 0.00 102.00 7.56 0.01 0.37 0.00 0.37 0.37 1.00
dm-3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-5 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.00 0.00 0.00 0.00 0.00 100.00 <---------------100% utilization
dm-6 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-7 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-8 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.00 0.00 0.00 0.00 0.00 100.00 <---------------100% utilization
dm-9 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.00 0.00 0.00 0.00 0.00 100.00 <---------------100% utilization
dm-10 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-11 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-12 0.00 0.00 0.00 1.00 0.00 4.00 8.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-13 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
dm-14 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

and an strace from the stuck samba service process shows the following, with the process getting stuck in a futex lock:
clock_gettime(CLOCK_MONOTONIC, {87850, 865762506}) = 0
futex(0x7efe9061bb54, FUTEX_WAIT_BITSET_PRIVATE, 1, {87851, 15762506}, ffffffff) = -1 ETIMEDOUT (Connection timed out)
futex(0x7efe9061bb28, FUTEX_WAKE_PRIVATE, 1) = 0

Cause

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