Deadlock in Berkley DB

[ruffinakoza]

An attempt to sync Fenia DB coincided with periodic archive script that runs db_checkpoint -1 && db_archive -d && db_dump fenia |bzip2 > ../fenia.dump.tbz2. Resulting stack trace:

#0  0x00007f45bb2359f3 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib/x86_64-linux-gnu/libpthread.so.0
#1  0x00007f45bba008ab in __db_pthread_mutex_lock () from /usr/lib/x86_64-linux-gnu/libdb_cxx-5.3.so
#2  0x00007f45bbaa858f in __lock_get_internal () from /usr/lib/x86_64-linux-gnu/libdb_cxx-5.3.so
#3  0x00007f45bbaa8ef6 in __lock_get () from /usr/lib/x86_64-linux-gnu/libdb_cxx-5.3.so
#4  0x00007f45bbad3c7a in __db_lget () from /usr/lib/x86_64-linux-gnu/libdb_cxx-5.3.so
#5  0x00007f45bba1d01c in __bam_search () from /usr/lib/x86_64-linux-gnu/libdb_cxx-5.3.so
#6  0x00007f45bba084db in ?? () from /usr/lib/x86_64-linux-gnu/libdb_cxx-5.3.so
#7  0x00007f45bba0cbeb in ?? () from /usr/lib/x86_64-linux-gnu/libdb_cxx-5.3.so
#8  0x00007f45bbac12b1 in __dbc_iput () from /usr/lib/x86_64-linux-gnu/libdb_cxx-5.3.so
#9  0x00007f45bbabc460 in __db_put () from /usr/lib/x86_64-linux-gnu/libdb_cxx-5.3.so
#10 0x00007f45bbad1f9b in __db_put_pp () from /usr/lib/x86_64-linux-gnu/libdb_cxx-5.3.so
#11 0x00007f45bb9f386f in Db::put(DbTxn*, Dbt*, Dbt*, unsigned int) () from /usr/lib/x86_64-linux-gnu/libdb_cxx-5.3.so
#12 0x00007f45bc7df762 in DbContext::put (this=this@entry=0x557f6ba58eb8, k=<optimized out>, k@entry=4179398893, dat=...) at ../../../dreamland_code/src/io/txncontext.cpp:383
#13 0x00007f45bc798112 in Scripting::Object::Manager::put (this=this@entry=0x557f6ba58eb8, id=4179398893, 
    s="<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<object type=\"ObjectWrapper\">\n  <guts>\n    <temperature>\n      <backref regtype=\"object\">-115568403</backref>\n      <target regtype=\"number\">20</target>\n    </te"...) at ../../../dreamland_code/src/fenia/object.cpp:221
#14 0x00007f45bc7997ea in Scripting::Object::save (this=0x557f70c4de40) at ../../../dreamland_code/src/fenia/object.cpp:124
#15 0x00007f45bc799cf9 in Scripting::Object::Manager::syncPut (this=this@entry=0x557f6ba58eb8, finishAt=finishAt@entry=0x7ffeab07afd0)
    at ../../../dreamland_code/src/fenia/object.cpp:245
#16 0x00007f45bc799db3 in Scripting::Object::Manager::sync (this=0x557f6ba58eb8, tickEnd=<optimized out>) at ../../../dreamland_code/src/fenia/object.cpp:304
#17 0x00007f45bcae924a in DreamLand::pulseEnd (this=this@entry=0x7ffeab07b100) at ../../dreamland_code/src/dreamland.cpp:200
#18 0x00007f45bcae9744 in DreamLand::run (this=0x7ffeab07b100) at ../../dreamland_code/src/dreamland.cpp:169
#19 0x0000557f69ca8f84 in main (argc=<optimized out>, argv=0x7ffeab07b5d8) at ../../dreamland_code/src/main.cpp:38

Lock wasn't released even after db_dump process was killed externally.