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HAProxy - Load balancer
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Aurelien DARRAGON 6b0b9bd39f BUG/MEDIUM: hlua: prevent deadlocks with main lua lock 
Main lua lock is used at various places in the code.

Most of the time it is used from unprotected lua environments,
in which case the locking is mandatory.
But there are some cases where the lock is attempted from protected
lua environments, meaning that lock is already owned by the current
thread. Thus new locking attempt should be skipped to prevent any
deadlocks from occuring.

To address this, "already_safe" lock hint was implemented in
hlua_ctx_init() function with commit bf90ce1
("BUG/MEDIUM: lua: dead lock when Lua tasks are trigerred")

But this approach is not very safe, for 2 reasons:

First reason is that there are still some code paths that could lead
to deadlocks.
For instance, in register_task(), hlua_ctx_init() is called with
already_safe set to 1 to prevent deadlock from occuring.

But in case of task init failure, hlua_ctx_destroy() will be called
from the same environment (protected environment), and hlua_ctx_destroy()
does not offer the already_safe lock hint.. resulting in a deadlock.

Second reason is that already_safe hint is used to completely skip
SET_LJMP macros (which manipulates the lock internally), resulting
in some logics in the function being unprotected from lua aborts in
case of unexpected errors when manipulating the lua stack (the lock
does not protect against longjmps)

Instead of leaving the locking responsibility to the caller, which is
quite error prone since we must find out ourselves if we are or not in
a protected environment (and is not robust against code re-use),
we move the deadlock protection logic directly in hlua_lock() function.

Thanks to a thread-local lock hint, we can easily guess if the current
thread already owns the main lua lock, in which case the locking attempt
is skipped. The thread-local lock hint is implemented as a counter so
that the lock is properly dropped when the counter reaches 0.
(to match actual lock() and unlock() calls)

This commit depends on "MINOR: hlua: simplify lua locking"
It may be backported to every stable versions.
[prior to 2.5 lua filter API did not exist, filter-related parts
should be skipped]
2023-04-05 08:58:17 +02:00
.github CI: exclude doc/{design-thoughts,internals} from spell check 2023-04-01 18:34:10 +02:00
addons MEDIUM: promex: Use the sedesc to report and detect end of processing 2023-04-05 08:57:06 +02:00
admin BUILD: halog: fix missing double-quote at end of help line 2022-11-25 11:11:41 +01:00
dev MEDIUM: ring: make the offset relative to the head/tail instead of absolute 2023-02-24 09:26:30 +01:00
doc MEDIUM: hlua_fcn/api: remove some old server and proxy attributes 2023-04-05 08:58:16 +02:00
examples EXAMPLES: remove completely outdated acl-content-sw.cfg 2022-05-30 18:14:24 +02:00
include MEDIUM: hlua_fcn: dynamic server iteration and indexing 2023-04-05 08:58:16 +02:00
reg-tests MEDIUM: hlua_fcn: dynamic server iteration and indexing 2023-04-05 08:58:16 +02:00
scripts SCRIPTS: run-regtests: add a version check 2022-11-30 18:44:33 +01:00
src BUG/MEDIUM: hlua: prevent deadlocks with main lua lock 2023-04-05 08:58:17 +02:00
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 MINOR: Configure the cpp userdiff driver for *.[ch] in .gitattributes 2021-02-22 18:17:57 +01:00
.gitignore CLEANUP: exclude udp-perturb with .gitignore 2022-09-16 15:47:04 +02:00
.mailmap DOC: update Tim's address in .mailmap 2021-09-16 09:14:14 +02:00
.travis.yml CI: travis-ci: temporarily disable arm64 builds 2021-08-07 07:28:15 +02:00
BRANCHES DOC: fix some spelling issues over multiple files 2021-01-08 14:53:47 +01:00
CHANGELOG [RELEASE] Released version 2.8-dev6 2023-03-28 13:58:56 +02:00
CONTRIBUTING CLEANUP: assorted typo fixes in the code and comments 2021-08-16 12:37:59 +02:00
INSTALL MINOR: version: mention that it's development again 2022-12-01 15:24:10 +01:00
LICENSE LICENSE: add licence exception for OpenSSL 2012-09-07 13:52:26 +02:00
MAINTAINERS CLEANUP: assorted typo fixes in the code and comments 2022-11-30 14:02:36 +01:00
Makefile MINOR: quic: Add a fake congestion control algorithm named "nocc" 2023-03-31 17:09:03 +02:00
README DOC: create a BRANCHES file to explain the life cycle 2019-06-15 22:00:14 +02:00
SUBVERS BUILD: use format tags in VERDATE and SUBVERS files 2013-12-10 11:22:49 +01:00
VERDATE [RELEASE] Released version 2.8-dev6 2023-03-28 13:58:56 +02:00
VERSION [RELEASE] Released version 2.8-dev6 2023-03-28 13:58:56 +02:00

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)