I randomly notice my OpenLDAP server freezes, and I can't udnerstand why.
I have a few LDAP clients (ldapsearch, a legacy Java app. and ApacheDirectoryStudio), running from different systems, either locally on the OpenLDAP server, or on another OpenLDAP
server, or on a remote workstation, and none manages to get an answer from OpenLDAP. The connection is established but each client gets stuck waiting for any result.

The last time, it occured only a few minutes after the OpenLDAP daemon was restarted, under very low load.
I use OpenLDAP 2.4.23, over Red Hat Enterprise Linux Server release 5.4 (Tikanga), Kernel version 2.6.18-164.el5, amd64 architecture over VMWare.
I also use BDB 4.8.30, and OpenLDAP's been compiled with the following options:

./configure --prefix=/opt/openldap-2.4.23 --enable-dynamic=yes --enable-dynlist=yes --enable-memberof=yes --enable-ppolicy=yes --enable-accesslog=yes --enable-sssvlv=yes

I noticed only 74 established connections on port 389 (according to netstat) when the freeze occurs.

The OpenLDAP server is set in syncrepl mirror mode replication, and the other OpenLDAP server (only used as a hot stand-by) works fine (but doesn't receive any load)

I only have the following lines at the end of the OpenLDAP log: (IP @ and suffixes voluntarily hidden)

Jul 12 10:19:32 dev-ldap1 slapd[28525]: conn=3377 fd=65 ACCEPT from IP=.......:3820 (IP=0.0.0.0:389)
Jul 12 10:19:32 dev-ldap1 slapd[28525]: conn=3377 op=0 BIND dn="employeeNumber=02071,ou=
people,dc=...." method=128
Jul 12 10:20:05 dev-ldap1 slapd[28525]: connection_input: conn=3377 deferring operation: binding
Jul 12 10:20:07 dev-ldap1 slapd[28525]: conn=3378 fd=66 ACCEPT from IP=......:3823 (IP=0.0.0.0:389)

The stack of the slapd process shows the following:

# pstack 28525
Thread 18 (Thread 0x408e4940 (LWP 28529)):
#0  0x0000003a53ad4018 in epoll_wait () from /lib64/libc.so.6
#1  0x000000000041d76e in ldap_pvt_sasl_mutex_dispose ()
#2  0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#3  0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 17 (Thread 0x41360940 (LWP 28530)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x0000000000492a80 in ldap_pvt_sasl_mutex_dispose ()
#8  0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000422736 in ldap_pvt_sasl_mutex_dispose ()
#11 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#12 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000422ec7 in ldap_pvt_sasl_mutex_dispose ()
#14 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#15 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#16 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#17 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#18 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 16 (Thread 0x41b61940 (LWP 28531)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x00000000004b4183 in ldap_pvt_sasl_mutex_dispose ()
#8  0x00000000004b802e in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000481a7a in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000482547 in ldap_pvt_sasl_mutex_dispose ()
#11 0x00000000004decab in ldap_pvt_sasl_mutex_dispose ()
#12 0x0000000000481b4a in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#14 0x000000000043be3e in ldap_pvt_sasl_mutex_dispose ()
#15 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#16 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#17 0x000000000043c83f in ldap_pvt_sasl_mutex_dispose ()
#18 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#19 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#20 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#21 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#22 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 15 (Thread 0x42362940 (LWP 28532)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x00000000004b4183 in ldap_pvt_sasl_mutex_dispose ()
#8  0x00000000004b802e in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000481a7a in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000482547 in ldap_pvt_sasl_mutex_dispose ()
#11 0x00000000004decab in ldap_pvt_sasl_mutex_dispose ()
#12 0x0000000000481b4a in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#14 0x000000000043be3e in ldap_pvt_sasl_mutex_dispose ()
#15 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#16 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#17 0x000000000043c83f in ldap_pvt_sasl_mutex_dispose ()
#18 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#19 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#20 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#21 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#22 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 14 (Thread 0x42b63940 (LWP 28533)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x00000000004b4183 in ldap_pvt_sasl_mutex_dispose ()
#8  0x00000000004b802e in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000481a7a in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000482547 in ldap_pvt_sasl_mutex_dispose ()
#11 0x00000000004decab in ldap_pvt_sasl_mutex_dispose ()
#12 0x0000000000481b4a in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#14 0x000000000043be3e in ldap_pvt_sasl_mutex_dispose ()
#15 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#16 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#17 0x000000000043c83f in ldap_pvt_sasl_mutex_dispose ()
#18 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#19 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#20 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#21 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#22 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 13 (Thread 0x43364940 (LWP 28534)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x00000000004b4183 in ldap_pvt_sasl_mutex_dispose ()
#8  0x00000000004b802e in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000481a7a in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000482547 in ldap_pvt_sasl_mutex_dispose ()
#11 0x00000000004decab in ldap_pvt_sasl_mutex_dispose ()
#12 0x0000000000481b4a in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#14 0x000000000043be3e in ldap_pvt_sasl_mutex_dispose ()
#15 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#16 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#17 0x000000000043c83f in ldap_pvt_sasl_mutex_dispose ()
#18 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#19 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#20 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#21 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#22 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 12 (Thread 0x43b65940 (LWP 28535)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x00000000004b4183 in ldap_pvt_sasl_mutex_dispose ()
#8  0x00000000004b802e in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000481a7a in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000482547 in ldap_pvt_sasl_mutex_dispose ()
#11 0x00000000004decab in ldap_pvt_sasl_mutex_dispose ()
#12 0x0000000000481b4a in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#14 0x000000000043be3e in ldap_pvt_sasl_mutex_dispose ()
#15 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#16 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#17 0x000000000043c83f in ldap_pvt_sasl_mutex_dispose ()
#18 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#19 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#20 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#21 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#22 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 11 (Thread 0x44366940 (LWP 29755)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x0000000000492a80 in ldap_pvt_sasl_mutex_dispose ()
#8  0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000422736 in ldap_pvt_sasl_mutex_dispose ()
#11 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#12 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000422ec7 in ldap_pvt_sasl_mutex_dispose ()
#14 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#15 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#16 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#17 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#18 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 10 (Thread 0x44b67940 (LWP 29756)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x00000000004b4183 in ldap_pvt_sasl_mutex_dispose ()
#8  0x00000000004b802e in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000481a7a in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000482547 in ldap_pvt_sasl_mutex_dispose ()
#11 0x00000000004decab in ldap_pvt_sasl_mutex_dispose ()
#12 0x0000000000481b4a in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#14 0x000000000043be3e in ldap_pvt_sasl_mutex_dispose ()
#15 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#16 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#17 0x000000000043c83f in ldap_pvt_sasl_mutex_dispose ()
#18 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#19 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#20 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#21 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#22 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 9 (Thread 0x45368940 (LWP 29757)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x0000000000492a80 in ldap_pvt_sasl_mutex_dispose ()
#8  0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000422736 in ldap_pvt_sasl_mutex_dispose ()
#11 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#12 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000422ec7 in ldap_pvt_sasl_mutex_dispose ()
#14 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#15 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#16 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#17 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#18 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 8 (Thread 0x45b69940 (LWP 29758)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd4ea in __lock_vec ()
#5  0x00002ba988bfe12b in __lock_vec_pp ()
#6  0x00000000004af514 in ldap_pvt_sasl_mutex_dispose ()
#7  0x00000000004af900 in ldap_pvt_sasl_mutex_dispose ()
#8  0x000000000048d323 in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#11 0x00000000004de44d in ldap_pvt_sasl_mutex_dispose ()
#12 0x000000000042ee25 in ldap_pvt_sasl_mutex_dispose ()
#13 0x00000000004319c8 in ldap_pvt_sasl_mutex_dispose ()
#14 0x0000000000432749 in ldap_pvt_sasl_mutex_dispose ()
#15 0x00000000004ae91b in ldap_pvt_sasl_mutex_dispose ()
#16 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#17 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#18 0x000000000043be3e in ldap_pvt_sasl_mutex_dispose ()
#19 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#20 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#21 0x000000000043c83f in ldap_pvt_sasl_mutex_dispose ()
#22 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#23 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#24 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#25 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#26 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 7 (Thread 0x4636a940 (LWP 29759)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x00000000004b4183 in ldap_pvt_sasl_mutex_dispose ()
#8  0x00000000004b802e in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000481a7a in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000482547 in ldap_pvt_sasl_mutex_dispose ()
#11 0x00000000004decab in ldap_pvt_sasl_mutex_dispose ()
#12 0x0000000000481b4a in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#14 0x000000000043be3e in ldap_pvt_sasl_mutex_dispose ()
#15 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#16 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#17 0x000000000043c83f in ldap_pvt_sasl_mutex_dispose ()
#18 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#19 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#20 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#21 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#22 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 6 (Thread 0x46b6b940 (LWP 29760)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba9886df7fb in ldap_pvt_thread_rmutex_lock ()
#2  0x00000000004d4c74 in ldap_pvt_sasl_mutex_dispose ()
#3  0x0000000000481b4a in ldap_pvt_sasl_mutex_dispose ()
#4  0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#5  0x00000000004de44d in ldap_pvt_sasl_mutex_dispose ()
#6  0x000000000042ee25 in ldap_pvt_sasl_mutex_dispose ()
#7  0x00000000004319c8 in ldap_pvt_sasl_mutex_dispose ()
#8  0x0000000000432749 in ldap_pvt_sasl_mutex_dispose ()
#9  0x00000000004ae91b in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#11 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#12 0x000000000043be3e in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#14 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#15 0x000000000043c83f in ldap_pvt_sasl_mutex_dispose ()
#16 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#17 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#18 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#19 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#20 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 5 (Thread 0x4736c940 (LWP 29761)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x00000000004b4183 in ldap_pvt_sasl_mutex_dispose ()
#8  0x00000000004b802e in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000481a7a in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000482547 in ldap_pvt_sasl_mutex_dispose ()
#11 0x00000000004decab in ldap_pvt_sasl_mutex_dispose ()
#12 0x0000000000481b4a in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#14 0x000000000043be3e in ldap_pvt_sasl_mutex_dispose ()
#15 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#16 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#17 0x000000000043c83f in ldap_pvt_sasl_mutex_dispose ()
#18 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#19 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#20 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#21 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#22 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 4 (Thread 0x47b6d940 (LWP 29762)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x00000000004b4183 in ldap_pvt_sasl_mutex_dispose ()
#8  0x00000000004b802e in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000481a7a in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000482547 in ldap_pvt_sasl_mutex_dispose ()
#11 0x00000000004decab in ldap_pvt_sasl_mutex_dispose ()
#12 0x0000000000481b4a in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#14 0x000000000043be3e in ldap_pvt_sasl_mutex_dispose ()
#15 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#16 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#17 0x000000000043c83f in ldap_pvt_sasl_mutex_dispose ()
#18 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#19 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#20 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#21 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#22 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 3 (Thread 0x4836e940 (LWP 29763)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x0000000000492a80 in ldap_pvt_sasl_mutex_dispose ()
#8  0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#10 0x00000000004758a4 in ldap_pvt_sasl_mutex_dispose ()
#11 0x000000000047ce54 in ldap_pvt_sasl_mutex_dispose ()
#12 0x00000000004214d3 in ldap_pvt_sasl_mutex_dispose ()
#13 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#14 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#15 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 2 (Thread 0x48b6f940 (LWP 29764)):
#0  0x0000003a5460ab99 in pthread_cond_wait@@GLIBC_2.3.2 ()
#1  0x00002ba988b6cdd2 in __db_pthread_mutex_lock ()
#2  0x00002ba988b6c426 in __db_tas_mutex_lock ()
#3  0x00002ba988bfcb49 in __lock_get_internal ()
#4  0x00002ba988bfd2c2 in __lock_get_pp ()
#5  0x00000000004af398 in ldap_pvt_sasl_mutex_dispose ()
#6  0x00000000004b04ca in ldap_pvt_sasl_mutex_dispose ()
#7  0x00000000004b4183 in ldap_pvt_sasl_mutex_dispose ()
#8  0x00000000004b802e in ldap_pvt_sasl_mutex_dispose ()
#9  0x0000000000481a7a in ldap_pvt_sasl_mutex_dispose ()
#10 0x0000000000482547 in ldap_pvt_sasl_mutex_dispose ()
#11 0x00000000004decab in ldap_pvt_sasl_mutex_dispose ()
#12 0x0000000000481b4a in ldap_pvt_sasl_mutex_dispose ()
#13 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#14 0x000000000043be3e in ldap_pvt_sasl_mutex_dispose ()
#15 0x0000000000481bc2 in ldap_pvt_sasl_mutex_dispose ()
#16 0x0000000000482127 in ldap_pvt_sasl_mutex_dispose ()
#17 0x000000000043c83f in ldap_pvt_sasl_mutex_dispose ()
#18 0x00000000004205a5 in ldap_pvt_sasl_mutex_dispose ()
#19 0x0000000000420b7f in ldap_pvt_sasl_mutex_dispose ()
#20 0x00002ba9886e08a8 in ldap_int_thread_pool_wrapper ()
#21 0x0000003a546064a7 in start_thread () from /lib64/libpthread.so.0
#22 0x0000003a53ad3c2d in clone () from /lib64/libc.so.6
Thread 1 (Thread 0x2ba988eb9bd0 (LWP 28525)):
#0  0x0000003a546077e5 in pthread_join () from /lib64/libpthread.so.0
#1  0x000000000041b3e2 in ldap_pvt_sasl_mutex_dispose ()
#2  0x000000000040960e in ldap_pvt_sasl_mutex_dispose ()
#3  0x0000003a53a1d994 in __libc_start_main () from /lib64/libc.so.6
#4  0x00000000004080d9 in ldap_pvt_sasl_mutex_dispose ()
#5  0x00007ffff6e2df58 in ?? ()
#6  0x0000000000000000 in ?? ()


I have 2 different suffixes, but didn't notice any obvious problem with the database or file system (space left, corruption, bad file owner and so on).
For example, the db_stat -c gives the following result on the main database:

579     Last allocated locker ID
0x7fffffff      Current maximum unused locker ID
9       Number of lock modes
10000   Maximum number of locks possible
10000   Maximum number of lockers possible
10000   Maximum number of lock objects possible
1       Number of lock object partitions
951     Number of current locks
1686    Maximum number of locks at any one time
16      Maximum number of locks in any one bucket
0       Maximum number of locks stolen by for an empty partition
0       Maximum number of locks stolen for any one partition
114     Number of current lockers
130     Maximum number of lockers at any one time
933     Number of current lock objects
1586    Maximum number of lock objects at any one time
3       Maximum number of lock objects in any one bucket
0       Maximum number of objects stolen by for an empty partition
0       Maximum number of objects stolen for any one partition
125M    Total number of locks requested (125419838)
125M    Total number of locks released (125418879)
0       Total number of locks upgraded
138     Total number of locks downgraded
15      Lock requests not available due to conflicts, for which we waited
0       Lock requests not available due to conflicts, for which we did not wait
0       Number of deadlocks
0       Lock timeout value
0       Number of locks that have timed out
0       Transaction timeout value
0       Number of transactions that have timed out
8MB 464KB       The size of the lock region
0       The number of partition locks that required waiting (0%)
0       The maximum number of times any partition lock was waited for (0%)
0       The number of object queue operations that required waiting (0%)
0       The number of locker allocations that required waiting (0%)
45      The number of region locks that required waiting (0%)
3       Maximum hash bucket length

I've also backed up the content of the /proc/28525 directory for further analysis. What else could I do ?