5:10 a.m.
Hi Kathy,
The procedure to diagnose hang looks nice. My understanding is that it
assumes that in deadlock situation the more we have threads waiting on a
resource, the more probable we have a hang/deadlock. Now because of the
dynamic of the server itself, on the configuration, on the type of
requests, on the monitoring of rwlock vs simple locks, on the impact on
gdb prone to stop threads on locks, this scripts may fails to detect
hang/deadlock.
ATM I see no specific 8.6 enhancements that can explain why the script
is failing now.
If the server is no longer responsive to a client request (keepalive
req), I suggest you collect pstacks, 'top -H -p `pidof ns-slapd`' and
db_stat -N -CA. If it is eating CPU you may looks at the activity of
thread consuming CPU. If it is not, it is possibly deadlock between
backend/database access.
Best regards
thierry
On 8/30/22 11:20 PM, Kathy Zhu via FreeIPA-users wrote:
Hi Team,
We used following to get the number of rwlocks for /usr/sbin/ns-slapd
process in Centos 7.9 to catch deadlocks:
PID=`pidof ns-slapd`
gdb -ex 'set confirm off' -ex 'set pagination off' -ex 'thread apply
all bt full' -ex 'quit' /usr/sbin/ns-slapd $PID |& grep
'^#0.*lock' |
grep pthread_rwlock | sort -u
That helped us to detect ns-slapd hang caused by deadlocks.
After migrating to Red Hat 8.6, we had a lot of hangs (dirsvr is
running but not responding) and could not find why. We use the same
above method, however, we are not able to catch anything. I wonder if
there is a different way to count the rwlocks in Red Hat 8.6?
We realize that there are multiple reasons to cause hangs, however, we
would like to rule out the possibility of the deadlock.
The OS and packages:
Red Hat Enterprise Linux release 8.6 (Ootpa)
ipa-server.x86_64 4.9.8-7.module+el8.6.0+14337+19b76db2
@rhel-8-for-x86_64-appstream-rpms
slapi-nis-0.56.6-4.module+el8.6.0+12936+736896b2.x86_64
389-ds-base-libs-1.4.3.28-6.module+el8.6.0+14129+983ceada.x86_64
389-ds-base-1.4.3.28-6.module+el8.6.0+14129+983ceada.x86_64
Many thanks.
Kathy.
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