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Aurelien DARRAGON 3ffbf3896d BUG/MEDIUM: httpclient/lua: fix a race between lua GC and hlua_ctx_destroy 
In bb581423b ("BUG/MEDIUM: httpclient/lua: crash when the lua task timeout
before the httpclient"), a new logic was implemented to make sure that
when a lua ctx destroyed, related httpclients are correctly destroyed too
to prevent a such httpclients from being resuscitated on a destroyed lua ctx.

This was implemented by adding a list of httpclients within the lua ctx,
and a new function, hlua_httpclient_destroy_all(), that is called under
hlua_ctx_destroy() and runs through the httpclients list in the lua context
to properly terminate them.

This was done with the assumption that no concurrent Lua garbage collection
cycles could occur on the same ressources, which seems OK since the "lua"
context is about to be freed and is not explicitly being used by other threads.

But when 'lua-load' is used, the main lua stack is shared between multiple
OS threads, which means that all lua ctx in the process are linked to the
same parent stack.
Yet it seems that lua GC, which can be triggered automatically under
lua_resume() or manually through lua_gc(), does not limit itself to the
"coroutine" stack (the stack referenced in lua->T) when performing the cleanup,
but is able to perform some cleanup on the main stack plus coroutines stacks
that were created under the same main stack (via lua_newthread()) as well.

This can be explained by the fact that lua_newthread() coroutines are not meant
to be thread-safe by design.
Source: http://lua-users.org/lists/lua-l/2011-07/msg00072.html (lua co-author)

It did not cause other issues so far because most of the time when using
'lua-load', the global lua lock is taken when performing critical operations
that are known to interfere with the main stack.
But here in hlua_httpclient_destroy_all(), we don't run under the global lock.

Now that we properly understand the issue, the fix is pretty trivial:

We could simply guard the hlua_httpclient_destroy_all() under the global
lua lock, this would work but it could increase the contention over the
global lock.

Instead, we switched 'lua->hc_list' which was introduced with bb581423b
from simple list to mt_list so that concurrent accesses between
hlua_httpclient_destroy_all and hlua_httpclient_gc() are properly handled.

The issue was reported by @Mark11122 on Github #2037.

This must be backported with bb581423b ("BUG/MEDIUM: httpclient/lua: crash
when the lua task timeout before the httpclient") as far as 2.5.
2023-02-22 11:44:22 +01:00
.github CI: Reformat matrix.py using black 2023-01-03 16:28:34 +01:00
addons BUG/MINOR: promex: Don't forget to consume the request on error 2023-01-13 09:45:23 +01:00
admin BUILD: halog: fix missing double-quote at end of help line 2022-11-25 11:11:41 +01:00
dev DEV: hpack: fix trash build regression 2023-01-27 10:22:20 +01:00
doc MINOR: startup: HAPROXY_STARTUP_VERSION contains the version used to start 2023-02-21 14:16:45 +01:00
examples
include BUG/MEDIUM: httpclient/lua: fix a race between lua GC and hlua_ctx_destroy 2023-02-22 11:44:22 +01:00
reg-tests BUG/MINOR: cache: Cache response even if request has "no-cache" directive 2023-02-21 18:35:41 +01:00
scripts SCRIPTS: run-regtests: add a version check 2022-11-30 18:44:33 +01:00
src BUG/MEDIUM: httpclient/lua: fix a race between lua GC and hlua_ctx_destroy 2023-02-22 11:44:22 +01:00
tests TESTS: add a unit test for one_among_mask() 2022-06-21 20:29:57 +02:00
.cirrus.yml CI: cirrus-ci: bump FreeBSD image to 13-1 2022-09-09 13:30:17 +02:00
.gitattributes
.gitignore CLEANUP: exclude udp-perturb with .gitignore 2022-09-16 15:47:04 +02:00
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BRANCHES
CHANGELOG [RELEASE] Released version 2.8-dev4 2023-02-14 16:55:17 +01:00
CONTRIBUTING
INSTALL MINOR: version: mention that it's development again 2022-12-01 15:24:10 +01:00
LICENSE
MAINTAINERS CLEANUP: assorted typo fixes in the code and comments 2022-11-30 14:02:36 +01:00
Makefile BUILD: makefile: fix PCRE overriding specific lib path 2023-02-03 09:42:49 +01:00
README
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VERDATE [RELEASE] Released version 2.8-dev4 2023-02-14 16:55:17 +01:00
VERSION [RELEASE] Released version 2.8-dev4 2023-02-14 16:55:17 +01:00

README 

The HAProxy documentation has been split into a number of different files for
ease of use.

Please refer to the following files depending on what you're looking for :

  - INSTALL for instructions on how to build and install HAProxy
  - BRANCHES to understand the project's life cycle and what version to use
  - LICENSE for the project's license
  - CONTRIBUTING for the process to follow to submit contributions

The more detailed documentation is located into the doc/ directory :

  - doc/intro.txt for a quick introduction on HAProxy
  - doc/configuration.txt for the configuration's reference manual
  - doc/lua.txt for the Lua's reference manual
  - doc/SPOE.txt for how to use the SPOE engine
  - doc/network-namespaces.txt for how to use network namespaces under Linux
  - doc/management.txt for the management guide
  - doc/regression-testing.txt for how to use the regression testing suite
  - doc/peers.txt for the peers protocol reference
  - doc/coding-style.txt for how to adopt HAProxy's coding style
  - doc/internals for developer-specific documentation (not all up to date)