[Nss-mysql-users] Locking Issues?

[Theo Zourzouvillys]

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mooo,

I've been having some problems recently while having users logging into one of 
our shell servers, where I get:

_nss_mysql_passwd_read_db: mysql_query failed: Lost connection to MySQL server 
during query

while our main SQL server is under heavy load.

Now i've investigated a bit, and it seemed like it was a lockign issue, where 
two threads/processes were makign a query using the same MYSQL *, so I 
investigated further, by changing:

#define lockm() \
if (m) { \
    pthread_mutex_lock(m); \
    _nss_mysql_log(LOG_ERR, "Locked Mutex: %p", m); \
} else  _nss_mysql_log(LOG_ERR, "*NOT* Locking Mutex!");

#define unlockm() \
if (m) { \
    pthread_mutex_unlock(m); \
     _nss_mysql_log(LOG_ERR, "UNLocked Mutex: %p", m); \
} else _nss_mysql_log(LOG_ERR, "*NOT* UnLocking Mutex!");

now running again in simulated situation where the MySQL server is heavily 
loaded, and debug enabled, i get...


nss-mysql[10674]: getpwnam called for zozo
nss-mysql[10674]: _nss_mysql_read_conf_file: called for section users
nss-mysql[1352]: getpwnam called for zozo
nss-mysql[1352]: _nss_mysql_read_conf_file: called for section users
nss-mysql[10674]: _nss_mysql_read_conf_file ended for section users
nss-mysql[10674]: _nss_mysql_check_connection called
nss-mysql[10674]: _nss_mysql_check_connection: found a saved MYSQL * 
(0x809bc38)
nss-mysql[1352]: _nss_mysql_read_conf_file ended for section users
nss-mysql[1352]: _nss_mysql_check_connection called
nss-mysql[1352]: _nss_mysql_check_connection: found a saved MYSQL * 
(0x809bc38)
nss-mysql[10674]: _nss_mysql_check_connection: sucessfully exiting
nss-mysql[1352]: _nss_mysql_check_connection: sucessfully exiting
nss-mysql[10674]: _nss_mysql_passwd_read_db called for user zozo
nss-mysql[1352]: _nss_mysql_passwd_read_db called for user zozo
nss-mysql[10674]: _nss_mysql_passwd_read_db: SQL statement: select 
Users.Username,Users.UID,NULL,Users.Name,Users.Shell,Users.Home,Users.GID 
from Users where Users.Username='zozo' and Users.UID is not null and '1=1' 
order by Users.UID
nss-mysql[1352]: _nss_mysql_passwd_read_db: SQL statement: select 
Users.Username,Users.UID,NULL,Users.Name,Users.Shell,Users.Home,Users.GID 
from Users where Users.Username='zozo' and Users.UID is not null and '1=1' 
order by Users.UID
nss-mysql[10674]: Locked Mutex: 0x4e6b75f0
nss-mysql[1352]: Locked Mutex: 0x4e6b75f0
nss-mysql[10674]: _nss_mysql_passwd_read_db: mysql_query failed: Lost 
connection to MySQL server during query
nss-mysql[10674]: UNLocked Mutex: 0x4e6b75f0
sshd[10674]: fatal: login_init_entry: Cannot find user "zozo"
nss-mysql[1352]: _nss_mysql_passwd_read_db: mysql_query failed: Lost 
connection to MySQL server during query
nss-mysql[1352]: UNLocked Mutex: 0x4e6b75f0

Now, errr, call me mad, but that should *not* be happening. I've spent all 
evening investigating how pthread_mutex_lock could possibly be locking the 
same mutex twice, but just can't see it.

any suggestions? or am i chasing in the wrong place? ;)


 ~ Theo

- -- 
Theo Zourzouvillys
 + Operations Manager
 + Associated Networks Limited
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