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13e86d947d
It is pretty similar to fbb934da90 ("BUG/MEDIUM: stick-table: fix a race
condition when updating the expiration task"). When the global management
task is running, at the end of its process function, it resets the expire
date by setting it to TICK_ETERNITY. In same time, a listener may reach a
global limit and decides to schedule the task. Thus it is possible to queue
the task and trigger the BUG_ON() on the expire date because its value was
set to TICK_ETERNITY in the means time:
FATAL: bug condition "task->expire == 0" matched at src/task.c:310
call trace(12):
| 0x662de8 [b8 01 00 00 00 c6 00 00]: __task_queue+0xc7/0x11e
| 0x63b03f [48 b8 04 00 00 00 05 00]: main+0x2535e
| 0x63ed1a [e9 d2 fd ff ff 48 8b 45]: listener_accept+0xf72/0xfda
| 0x6a36d3 [eb 01 90 c9 c3 55 48 89]: sock_accept_iocb+0x82/0x87
| 0x6af22f [48 8b 05 ca f9 13 00 8b]: fd_update_events+0x35a/0x497
| 0x42a7a8 [89 45 d8 83 7d d8 02 75]: main-0x1eb539
| 0x6158fb [48 8b 05 e6 06 1c 00 64]: run_poll_loop+0x2e7/0x319
| 0x615b6c [48 8b 05 ed 65 1d 00 48]: main-0x175
| 0x7ffff775bded [e9 69 fe ff ff 48 8b 4c]: libc:+0x8cded
| 0x7ffff77e1370 [48 89 c7 b8 3c 00 00 00]: libc:+0x112370
To fix the bug, a RW lock is introduced. It is used to fix the race
condition. A read lock is taken when the task is scheduled, in
listener_accpet() and a write lock is used at the end of process function to
set the expire date to TICK_ETERNITY. This lock should not be used very
often and most of time by "readers". So, the impact should be really
limited.
This patch should fix the issue #1930. It must be backported as far as 1.8
with some cautions because the code has evolved a lot since then.
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)