The current lock/refcount handling of the global data table is (very slightly)
racy during reloads and could theoretically lead to a crash.
- the *global_data pointer itself must be accessed and swapped out atomatically
to eliminate possible race conditions
- reading the pointer _and_ increasing the reference count for the pointed-to
table atomically is only possible with a global lock
- usually there are only one or two tables in existence at any given time, so
we can drop the per-table lock and use the global lock to also protect the
per-table reference count (this could be done with an atomic int as well, but
we already have a lock anyway)
- the global lock implicitly guarantees both memory fences and compiler fences
Came up in a (marginally) related discussion in #4809
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You can view, comment on, or merge this pull request online at:
https://github.com/kamailio/kamailio/pull/4819
-- Commit Summary --
* carrierroute: improved threading safety
-- File Changes --
M src/modules/carrierroute/cr_data.c (48)
M src/modules/carrierroute/cr_data.h (2)
-- Patch Links --
https://github.com/kamailio/kamailio/pull/4819.patch
https://github.com/kamailio/kamailio/pull/4819.diff
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