What handler/module is expected to process this request?  Usually the  body isn't read until the handler has control. Can you try again with -O0 and don't set a breakpoint, just get a backtrace of the hung thread.

We're running in a mod_perl environment. If I let the process hang I can't get a backtrace.

Rebuilt with the -O0 option I was able to get some more information. In this environment the doc root is "/opt/product/apache/htdocs".

(gdb) bt
#0  ap_run_handler (r=0xce37d20) at config.c:157
#1  0x0807fb5c in ap_invoke_handler (r=0xce37d20) at config.c:376
#2  0x080a33b2 in ap_process_request (r=0xce37d20) at http_request.c:282
#3  0x080a06e0 in ap_process_http_connection (c=0xcb53d08) at http_core.c:190
#4  0x08086b8f in ap_run_process_connection (c=0xcb53d08) at connection.c:43
#5  0x08086fe5 in ap_process_connection (c=0xcb53d08, csd=0xcb53b70) at connection.c:190
#6  0x080a9490 in child_main (child_num_arg=0) at prefork.c:667
#7  0x080a963c in make_child (s=0x8dd2ca8, slot=0) at prefork.c:768
#8  0x080a96af in startup_children (number_to_start=1) at prefork.c:786
#9  0x080a9ae0 in ap_mpm_run (_pconf=0x8dce0a8, plog=0x8e04180, s=0x8dd2ca8) at prefork.c:1007
#10 0x08069dd1 in main (argc=3, argv=0xffa79174) at main.c:753
(gdb) p r
$1 = (request_rec *) 0xce37d20
(gdb) p *r
$2 = {pool = 0xce37ce0, connection = 0xcb53d08, server = 0x8dd2ca8, next = 0x0, prev = 0x0, main = 0x0,
  the_request = 0xce38c60 "POST /sla/create/index.html HTTP/1.1", assbackwards = 0, proxyreq = 0, header_only = 0,
  protocol = 0xce38d00 "HTTP/1.1", proto_num = 1001, hostname = 0xce39220 "209.211.205.181",
  request_time = 1369158013800915, status_line = 0x0, status = 200, method = 0xce38cb0 "POST", method_number = 2,
  allowed = 0, allowed_xmethods = 0x0, allowed_methods = 0xce37ec0, sent_bodyct = 0, bytes_sent = 0, mtime = 0,
  chunked = 0, range = 0x0, clength = 0, remaining = 0, read_length = 0, read_body = 0, read_chunked = 0,
  expecting_100 = 0, headers_in = 0xce37ef0, headers_out = 0xce38380, err_headers_out = 0xce38528,
  subprocess_env = 0xce38138, notes = 0xce38680, content_type = 0x8e90c48 "text/html",
  handler = 0x8ded1c8 "perl-script", content_encoding = 0x0, content_languages = 0x0, vlist_validator = 0x0,
  user = 0x0, ap_auth_type = 0x0, no_cache = 0, no_local_copy = 0,
  unparsed_uri = 0xce38cd0 "/sla/create/index.html", uri = 0xce38ce8 "/sla/create/index.html",
  filename = 0xce39348 "/opt/product/apache/htdocs/sla/create/index.html",
  canonical_filename = 0xce39348 "/opt/product/apache/htdocs/sla/create/index.html", path_info = 0xce392c1 "",
  args = 0x0, finfo = {pool = 0xce37ce0, valid = 7598960, protection = 1604, filetype = APR_REG, user = 504,
    group = 110, inode = 6657732, device = 64769, nlink = 1, size = 2608, csize = 4096, atime = 1369157418000000,
    mtime = 1360861380000000, ctime = 1360861380000000,
    fname = 0xce39290 "/opt/product/apache/htdocs/sla/create/index.html", name = 0x0, filehand = 0x0}, parsed_uri = {
    scheme = 0x0, hostinfo = 0x0, user = 0x0, password = 0x0, hostname = 0x0, port_str = 0xce39239 "8080",
    path = 0xce38ce8 "/sla/create/index.html", query = 0x0, fragment = 0x0, hostent = 0x0, port = 8080,
    is_initialized = 1, dns_looked_up = 0, dns_resolved = 0}, used_path_info = 2, per_dir_config = 0xce39590,
  request_config = 0xce387d8, htaccess = 0x0, output_filters = 0xccf1818, input_filters = 0xce39240,
  proto_output_filters = 0xce38be0, proto_input_filters = 0xce39240, eos_sent = 0}


Stepping from here, the process hangs. Running pstack from another window returns nothing.

(In reply to comment #0)
> I find no function definition in the apache source tree for
> ap_run_handler(). 
> 
> Line 157 in config.c is
> AP_IMPLEMENT_HOOK_RUN_FIRST(int, handler, (request_rec *r), (r), DECLINED)
> 
> Following the code for definitions of this macro, leads me to a rather
> obfuscated define in apr_hooks.h, line 358
> /** macro to implement the hook */
> #define APR_IMPLEMENT_EXTERNAL_HOOK_BASE(ns,link,name) \
> link##_DECLARE(void) ns##_hook_##name(ns##_HOOK_##name##_t *pf,const char *
> const *aszPre, \
>                                       const char * const *aszSucc,int
> nOrder) \
>     { \
> 
> The apache docs are no help, simply notes it as an internal macro.
> 
The function to look for is ap_hook_handler.
This is found in several modules.
One example is server/core.c:
   ap_hook_handler(default_handler,NULL,NULL,APR_HOOK_REALLY_LAST);
This will cause the default_handler function in core.c to be called whenever ap_run_handler is called.
The following documentation may help explain this:
- http://httpd.apache.org/docs/2.2/developer/hooks.html

Perhaps mod_perl should have something like this as well.

I set breakpoints at ap_hook_handler and default_handler, neither of them were reached.

I ran the same form with a small data set so it completed. At the breakpoint for ap_run_handler, I did step and it came back quickly with the next line further down, a call to ap_invoke_handler [config.c:378]. And the form has returned. No meaningful difference in contents of the request object.

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