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reader_concurrency_semaphore: fix leak workaround

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`e4da0afb8d5491bf995cbd1d7a7efb966c79ac34` introduces a protection
against resources that are "made up" of thin air to
`reader_concurrency_semaphore`. If there are more `_resources` than
the `_initial_resources`, it means there is a negative leak, and
`on_internal_error_noexcept` is called. In addition to it,
`_resources` is set to `std::max(_resources, _initial_resources)`.

However, the commit message of `e4da0afb8d5491bf995cbd1d7a7efb966c79ac34`
states the opposite: "The detection also clamps the
_resources to _initial_resources, to prevent any damage".

Before this commit, the protection mechanism doesn't clamp
`_resources` to `_initial_resources` but instead keeps `_resources` high,
possibly even indefinitely growing. This commit changes `std::max` to
`std::min` to make the code behave as intended.

Fixes: SCYLLADB-1014
Refs: SCYLLADB-163

Closes scylladb/scylladb#28982

(cherry picked from commit 9247dff8c2)

Closes scylladb/scylladb#28988

Closes scylladb/scylladb#29196
This commit is contained in:
Andrzej Jackowski
2026-03-10 12:09:53 +01:00
committed by Marcin Maliszkiewicz
parent ba3b7360e0
commit 7b97fe4a92
1 changed files with 2 additions and 2 deletions
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4
reader_concurrency_semaphore.cc
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@@ -1023,8 +1023,8 @@ void reader_concurrency_semaphore::signal(const resources& r) noexcept {
on_internal_error_noexcept(rcslog,
format("reader_concurrency_semaphore::signal(): semaphore {} detected resource leak, available {} exceeds initial {}", _name,
_resources, _initial_resources));
_resources.count = std::max(_resources.count, _initial_resources.count);
_resources.memory = std::max(_resources.memory, _initial_resources.memory);
_resources.count = std::min(_resources.count, _initial_resources.count);
_resources.memory = std::min(_resources.memory, _initial_resources.memory);
}
maybe_wake_execution_loop();
}