mpm_event: wakeup the listener to re-enable listening sockets.

When listening sockets are disabled (too many connections) and the number of
workers / active connections comes back below the limit, we need to wake up
the listener to re-enable them.

Add a new connections_above_limit() helper to determine when this applies.


Follow up to r1819855: CHANGES entry.


Submitted by: ylavic
Reviewed by: ylavic, jim, icing


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mpm_event(opt): avoid casts/comparisons from unsigned to signed (atomics).


mpm_event/worker: make ap_queue_term() atomic (acquire/release the mutex once).


mpm_event: ap_queue_info_try_get_idler() may atomically decrement and then
re-increment the number idlers if it went under or to zero.  We can avoid
this by switching to a compare-and-swap scheme.


mpm_event: avoid unexpected compiler optimizations.

Make sure the compiler doesn't play games with our synchronization variables
by marking them volatile.


mpm_event: make sure wakeup_listener() does its minimal job.

Even if the listener thread is not created yet (i.e. about to be), we must
still tell it to leave, and terminate the worker queue in any case.


mpm_event: worker factor vs pollset.

Make sure the worker factor is at least one (w.r.t. WORKER_FACTOR_SCALE), and
use it to size the pollset appropriately (including K-A and lingering close
connections), in addition to the listening sockets.


mpm_event: remove atomics for timeout_queue's total counter.

It's always updated under the timeout_mutex lock, or read for logging and
scoreboard updates (not critical).

For the read cases a volatile access is enough, while removing the atomic ops
for the already protected write cases saves cycles and context switches.


Submitted by: ylavic
Reviewed by: ylavic, jim, icing


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1823642 13f79535-47bb-0310-9956-ffa450edef68

event: minify local variables scope.


event: have_idle_worker must not be cleared in every listener_thread iteration.
Fixes bug when workers were not stopped after graceful restart (introduced in
                                                                r1605328).


Submitted by: takashi, jkaluza
Reviewed by: ylavic, jim, icing


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Merge of r1823179 from trunk.

config.layout: Add Fedora layout.


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Merge of r1605328,r1629576,r1643279,r1703241,r1802535,r1819847,r1819848,r1819852,r1819853,r1819855,r1821562,r1821558,r1821561,r1821595 from trunk

  *) event: staging changes (incremental patches) to sync 2.4.x with trunk.



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* modules/ssl/ssl_engine_config.c (ssl_cmd_SSLCompression): Fail if
  enabled *and* if OpenSSL does not make any compression methods
  available.  Tweak wording for failure without SSL_OP_NO_COMPRESSION.

Submitted by: jorton
Reviewed by: jorton, jim, ylavic


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* support/Makefile.in, acinclude.m4: Add OpenSSL libraries at the end of the
  ab link line, not the start.

[too boring for CHANGES]

Submitted by: jorton
Reviewed by: jorton, jim, ylavic


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* modules/lua/config.m4: Link mod_lua against -lcrypt if available,
  since mk_password_hash() can use crypt().

[too boring for CHANGES]

Submitted by: jorton
Reviewed by: jorton, jim, ylavic


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* mod_log_debug docs: Fix the IS_SUBREQ example

Submitted by: jkaluza
Reviewed by: jorton


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mod_md: merged copyright de-advertisements.
 


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mpm_{event,worker}: Mask signals for threads created by modules in child init.

PR 62009, so that they don't receive (implicitely) the ones meant for the MPM.

Inspired by: Armin Abfalterer <a.abfalterer gmail.com>


Follow up to r1821504: same comment in event than in worker.


Proposed by: ylavic
Reviewed by: ylavic, icing, covener


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Translated by: Nilgün Belma Bugüner <nilgun belgeler.gen.tr>
Reviewed by:  Orhan Berent <berent belgeler.gen.tr> 


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