I run php 4.1.2 module with apache 1.3.22 on Debian 3.0 and kernel 2.2.20, glibc version libc6-2.2.4-7.
PHP configure line:
./configure' '--prefix=/usr/local/php4' '--with-apxs=/usr/local/apache/bin/apxs' '--with-mysql' '--with-pgsql' '--with-gd' '--enable-ftp' '--with-mail' '--with-jpeg-dir' '--enable-dbase' '--with-freetype-dir' '--enable-gd-native-ttf' '--with-openssl=shared' '--with-curl=shared' '--with-imap' '--enable-trans-sid' '--with-zlib'

Sometimes one or more apache processes hang on, using most of CPU time. This processes don't stop, I must kill them by kill -9 pid.
Stack of this processes look like:
-----------------------------
process hanged after running php script
-----------------------------
#0  0x4010fd4f in free () from /lib/libc.so.6
#1  0x4010fac3 in free () from /lib/libc.so.6
#2  0x402fd88c in shutdown_memory_manager (silent=1, clean_cache=0)
    at zend_alloc.c:485
#3  0x40323880 in php_request_shutdown (dummy=0x0) at main.c:742
#4  0x40320993 in apache_php_module_main (r=0x846120c,
display_source_mode=0)
    at sapi_apache.c:96
#5  0x4032143e in send_php (r=0x846120c, display_source_mode=0,
filename=0x0)
    at mod_php4.c:575
#6  0x403214a5 in send_parsed_php (r=0x846120c) at mod_php4.c:590
#7  0x08076079 in ap_invoke_handler ()
#8  0x0808b3cf in process_request_internal ()
#9  0x0808b436 in ap_process_request ()
#10 0x08082246 in child_main ()
#11 0x080824ea in make_child ()
#12 0x08082878 in perform_idle_server_maintenance ()
#13 0x08082e4c in standalone_main ()
#14 0x080834ac in main ()
#15 0x400ba65f in __libc_start_main () from /lib/libc.so.6
-----------------------------
process hanged after display image
-----------------------------
#0  0x4010fd4f in free () from /lib/libc.so.6
#1  0x4010fac3 in free () from /lib/libc.so.6
#2  0x4031b15a in zend_hash_del_key_or_index (ht=0x859c030, 
    arKey=0x4047ea31 "rename", nKeyLength=7, h=0, flag=0) at zend_hash.c:517
#3  0x40319662 in zend_unregister_functions (functions=0x404a1bd0, count=-1,
    function_table=0x0) at zend_API.c:1085
#4  0x4031979d in module_destructor (module=0x858b5d0) at zend_API.c:1127
#5  0x4031b1de in zend_hash_destroy (ht=0x404c91e0) at zend_hash.c:541
#6  0x4031618f in zend_shutdown () at zend.c:494
#7  0x40323e8f in php_module_shutdown () at main.c:995
#8  0x40323e5c in php_module_shutdown_wrapper (sapi_globals=0x40498c60)
    at main.c:972
#9  0x403219c1 in php_child_exit_handler (s=0x80c0a44, p=0x870b4cc)
    at mod_php4.c:816
#10 0x0807860c in ap_child_exit_modules ()  
#11 0x0807eb0f in clean_child_exit ()
#12 0x0808099a in just_die ()  
#13 0x080809bf in usr1_handler ()
#14 0x400ca848 in sigaction () from /lib/libc.so.6
#15 0x0807ecfc in accept_mutex_on_sysvsem ()
#16 0x08081e39 in child_main ()
#17 0x080824ea in make_child ()
#18 0x08082878 in perform_idle_server_maintenance ()
#19 0x08082e4c in standalone_main ()
#20 0x080834ac in main ()
#21 0x400ba65f in __libc_start_main () from /lib/libc.so.6