When Apache is started with PHP using APC, all processes immedately go into this infinite loop, and never seem to serve any requests:

legolas:/web/apache/logs# strace -p 13980
Process 13980 attached - interrupt to quit
fcntl64(5, F_SETLKW, {type=F_WRLCK, whence=SEEK_SET, start=0, len=1}) = 0
fcntl64(5, F_SETLK, {type=F_UNLCK, whence=SEEK_SET, start=0, len=1}) = 0
fcntl64(5, F_SETLKW, {type=F_WRLCK, whence=SEEK_SET, start=0, len=1}) = 0
fcntl64(5, F_SETLK, {type=F_UNLCK, whence=SEEK_SET, start=0, len=1}) = 0
fcntl64(5, F_SETLKW, {type=F_WRLCK, whence=SEEK_SET, start=0, len=1}) = 0
fcntl64(5, F_SETLK, {type=F_UNLCK, whence=SEEK_SET, start=0, len=1}) = 0
fcntl64(5, F_SETLKW, {type=F_WRLCK, whence=SEEK_SET, start=0, len=1}) = 0
fcntl64(5, F_SETLK, {type=F_UNLCK, whence=SEEK_SET, start=0, len=1}) = 0
fcntl64(5, F_SETLKW, {type=F_WRLCK, whence=SEEK_SET, start=0, len=1}) = 0
fcntl64(5, F_SETLK, {type=F_UNLCK, whence=SEEK_SET, start=0, len=1}) = 0
fcntl64(5, F_SETLKW, {type=F_WRLCK, whence=SEEK_SET, start=0, len=1}) = 0
fcntl64(5, F_SETLK, {type=F_UNLCK, whence=SEEK_SET, start=0, len=1}) = 0
fcntl64(5, F_SETLKW, {type=F_WRLCK, whence=SEEK_SET, start=0, len=1}) = 0


#0  0x4013e1ef in fcntl () from /lib/tls/libc.so.6
#1  0x40d06807 in lock_reg (fd=-512, cmd=-512, type=-512, offset=-512, whence=-512, len=-512) at /root/APC-2.0.4/apc_fcntl.c:56
#2  0x40d06856 in apc_fcntl_lock (fd=-512) at /root/APC-2.0.4/apc_fcntl.c:61
#3  0x40d06fd9 in apc_sma_free (p=0x42be1620) at /root/APC-2.0.4/apc_sma.c:338
#4  0x40d0561d in my_destroy_zval (src=0x428558a4, deallocate=0x40d06fb0 <apc_sma_free>) at /root/APC-2.0.4/apc_compile.c:685
#5  0x40d0591b in my_destroy_op_array (src=0x42a07858, deallocate=0x40d06fb0 <apc_sma_free>) at /root/APC-2.0.4/apc_compile.c:824
#6  0x40d059ce in my_free_function (src=0x42a07858, deallocate=0x40d06fb0 <apc_sma_free>) at /root/APC-2.0.4/apc_compile.c:851
#7  0x40d05865 in my_destroy_hashtable (src=0x42823db0, free_fn=0x40d059b0 <my_free_function>, deallocate=0x40d06fb0 <apc_sma_free>)
    at /root/APC-2.0.4/apc_compile.c:799
#8  0x40d057ab in my_destroy_class_entry (src=0x42823d98, deallocate=0x40d06fb0 <apc_sma_free>) at /root/APC-2.0.4/apc_compile.c:770
#9  0x40d05afe in apc_free_classes (src=0x42a513b0, deallocate=0x40d06fb0 <apc_sma_free>) at /root/APC-2.0.4/apc_compile.c:899
#10 0x40d0453e in apc_cache_free_entry (entry=0x428d49f0) at /root/APC-2.0.4/apc_cache.c:381
#11 0x40d05f78 in cache_compile_results (key={device = 2051, inode = 3403933, mtime = 1096028058},
    filename=0x428d49f0 "PÞ\236Bp\211\211Bx\t\224B°\023¥B", op_array=0x7, functions=0xbfff9770, classes=0xfffffe00) at /root/APC-2.0.4/apc_main.c:139
#12 0x40d06141 in my_compile_file (h=0xbfffa160, type=8) at /root/APC-2.0.4/apc_main.c:185
#13 0x408f266a in execute (op_array=0x8167f3c) at /usr/src/php-4.3.9RC3/Zend/zend_execute.c:2161
#14 0x40d06186 in my_execute (op_array=0x8167f3c) at /root/APC-2.0.4/apc_main.c:199
#15 0x408f23ae in execute (op_array=0x815c624) at /usr/src/php-4.3.9RC3/Zend/zend_execute.c:2210
#16 0x40d06186 in my_execute (op_array=0x815c624) at /root/APC-2.0.4/apc_main.c:199
#17 0x408e2711 in zend_execute_scripts (type=8, retval=0x0, file_count=3) at /usr/src/php-4.3.9RC3/Zend/zend.c:891
#18 0x408b60af in php_execute_script (primary_file=0xbfffd9e0) at /usr/src/php-4.3.9RC3/main/main.c:1735
#19 0x408f51ce in apache_php_module_main (r=0x8156984, display_source_mode=0) at /usr/src/php-4.3.9RC3/sapi/apache/sapi_apache.c:54
#20 0x408f5d8c in send_php (r=0x8156984, display_source_mode=0, filename=0x0) at /usr/src/php-4.3.9RC3/sapi/apache/mod_php4.c:621
#21 0x408f5f3d in send_parsed_php (r=0xfffffe00) at /usr/src/php-4.3.9RC3/sapi/apache/mod_php4.c:636
#22 0x0806d29e in ap_invoke_handler ()
#23 0x0808373b in process_request_internal ()
#24 0x08083ba5 in ap_internal_redirect ()
#25 0x0805b94a in handle_dir ()
#26 0x0806d29e in ap_invoke_handler ()
#27 0x0808373b in process_request_internal ()
#28 0x08083798 in ap_process_request ()
#29 0x0807a0a3 in child_main ()
#30 0x0807a334 in make_child ()
#31 0x0807a3dd in startup_children ()
#32 0x0807aaf2 in standalone_main ()
#33 0x0807b3a0 in main ()