Bug#480210: apache2-mpm-prefork: Stale child threads not serving requests or timing out

[Henri Valta <henri.valta@kemi.fi>]

Not 100% sure if this is the same problem, but the effect is the same.

AMD64 machine,
Latest packages from Sid/Experimental:
apache2  2.2.8-4
php5/libapache2-mod-php5  5.2.6-1
libmysqlclient15off  5.1.19beta-1

MySQL server is on the same machine,
mysql-server  5.1.24rc-1

Backtrace from hung process without debug packages installed:

(gdb) bt full
#0  0x00007fc33540d34e in __lll_lock_wait_private () from /lib/libpthread.so.0
#1  0x00007fc33540aab2 in _L_lock_21 () from /lib/libpthread.so.0
#2  0x00007fc33540a91e in pthread_cond_destroy@@GLIBC_2.3.2 () from 
/lib/libpthread.so.0
#3  0x00007fc33434359b in my_thread_global_end () from 
/usr/lib/libmysqlclient_r.so.15
#4  0x00007fc33433ebaa in my_end () from /usr/lib/libmysqlclient_r.so.15
#5  0x00007fc33433d951 in mysql_server_end () from 
/usr/lib/libmysqlclient_r.so.15
#6  0x00007fc32a58eba8 in zm_shutdown_mysql () from 
/usr/lib/php5/20060613/mysql.so
#7  0x00007fc32f008df1 in module_destructor () from 
/usr/lib/apache2/modules/libphp5.so
#8  0x00007fc32f00f71a in ?? () from /usr/lib/apache2/modules/libphp5.so
#9  0x00007fc32f00f988 in zend_hash_graceful_reverse_destroy () from 
/usr/lib/apache2/modules/libphp5.so
#10 0x00007fc32f004ee7 in zend_shutdown () from 
/usr/lib/apache2/modules/libphp5.so
#11 0x00007fc32efc14ca in php_module_shutdown () from 
/usr/lib/apache2/modules/libphp5.so
#12 0x00007fc32efc1569 in php_module_shutdown_wrapper () from 
/usr/lib/apache2/modules/libphp5.so
#13 0x00007fc32f086861 in ?? () from /usr/lib/apache2/modules/libphp5.so
#14 0x00007fc3356328ad in ?? () from /usr/lib/libapr-1.so.0
#15 0x00007fc335632edd in apr_pool_destroy () from /usr/lib/libapr-1.so.0
#16 0x000000000044b00e in ?? ()
#17 0x000000000044b4d9 in ?? ()
#18 0x000000000044b675 in ?? ()
#19 0x000000000044b717 in ?? ()
#20 0x000000000044c1f1 in ap_mpm_run ()
#21 0x0000000000425ab2 in main ()