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[libdbi-users] Possible dbd_mysql thread unsafe problem?
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From: Ethan F. <et...@re...> - 2019-11-13 21:35:27
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I am having a problem with libdbd_mysql on linux (Ubuntu 19.10) reagding thread fasety. There used to be two versions of libmysqlclient, one was thread safe, one was not. However, now there seems to be only one client library, which I understood was thread safe: libmysqlclient.so.21. Any insight into the dump below would be greatly appreciated! Ethan... Here is a valgrind dump of a read-already-freed error that occurs in what I will call thread #3 when it attempts to connect to MySQL. This thread has it's own libdbi instance, yet mysql_real_connect is trying to read memory allocated by the first thread (thread #1) that first called mysql_real_connect, after that same memory was freed by another thread (thread #2) that called mysql_server_end as it was finishing. Each thread has it's own libdbi instance, so why is libmysqlclient sharring memory between threads? It's looking like the libmysqlclient isn't thread safe. ==2828== Invalid read of size 1 ==2828== at 0x4A3A042: strlen (vg_replace_strmem.c:461) ==2828== by 0x141A46C1: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141A5468: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141A54A8: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141A373E: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x4FE041E: __pthread_once_slow (pthread_once.c:116) ==2828== by 0x141A320D: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141A41B2: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141A429E: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x1415472B: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x1415492A: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141577A8: mysql_real_connect (in /usr/lib/x86_64- linux-gnu/libmysqlclient.so.21.1.17) ==2828== by 0x12F47435: dbd_connect (in /usr/lib/x86_64-linux- gnu/dbd/libdbdmysql.so) ==2828== by 0x4DC37AE: dbi_conn_connect (in /usr/lib/x86_64-linux- gnu/libdbi.so.1.1.0) ==2828== by 0x134BFA: dbSetupConnection (database.c:211) ==2828== by 0x1357F6: DeleteLogEntry (database.c:440) ==2828== by 0x131ECE: taskCallProcInThread (tasks.c:73) ==2828== by 0x4FD7668: start_thread (pthread_create.c:479) ==2828== by 0x567B322: clone (clone.S:95) Memory was freed in a thread (lets call it thread #2) that ran and completed. It created it's own dbi instance, did it's thing, and then closed it's MySQL connection and shutdown the instance. So why is it freeing memory deep in the mysql driver that it did not allocate? ==2828== Address 0x1343e698 is 424 bytes inside a block of size 4,088 free'd ==2828== at 0x4A37F90: free (vg_replace_malloc.c:540) ==2828== by 0x141A9B8A: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141A8756: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x14148982: mysql_server_end (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x12F4684C: dbd_finalize (in /usr/lib/x86_64-linux- gnu/dbd/libdbdmysql.so) ==2828== by 0x4DC2E4D: dbi_shutdown_r (in /usr/lib/x86_64-linux- gnu/libdbi.so.1.1.0) ==2828== by 0x134440: dbi_instance_free (database.c:56) ==2828== by 0x4FD6600: __nptl_deallocate_tsd.part.0 (pthread_create.c:301) ==2828== by 0x4FD7689: __nptl_deallocate_tsd (pthread_create.c:256) ==2828== by 0x4FD7689: start_thread (pthread_create.c:490) ==2828== by 0x567B322: clone (clone.S:95) This is in the first thread in the program to make use of libdbi/MySQL, and it is still running/connected to MySQL using a unique libdbi intance. ==2828== Block was alloc'd at ==2828== at 0x4A36E96: malloc (vg_replace_malloc.c:309) ==2828== by 0x141A9A30: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141A9AEB: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141A4E1C: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x1419CFA0: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x1419D95E: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x1416FD29: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141A2A66: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141A3771: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x4FE041E: __pthread_once_slow (pthread_once.c:116) ==2828== by 0x141A320D: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141A41B2: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141A429E: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x1415472B: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x1415492A: ??? (in /usr/lib/x86_64-linux- gnu/libmysqlclient.so.21.1.17) ==2828== by 0x141577A8: mysql_real_connect (in /usr/lib/x86_64- linux-gnu/libmysqlclient.so.21.1.17) ==2828== by 0x12F47435: dbd_connect (in /usr/lib/x86_64-linux- gnu/dbd/libdbdmysql.so) ==2828== by 0x4DC37AE: dbi_conn_connect (in /usr/lib/x86_64-linux- gnu/libdbi.so.1.1.0) ==2828== by 0x134BFA: dbSetupConnection (database.c:211) ==2828== by 0x13D2F4: GetItemMetaData (database.c:2960) ==2828== |
