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paxos: do not signal semaphore if it was not acquired

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The guard signals a semaphore during destruction if it is marked as
locked, but currently it may be marked as locked even if locking failed.
Fix this by using semaphore_units instead of managing the locked flag
manually.

Fixes: https://github.com/scylladb/scylladb/issues/19698
This commit is contained in:
Gleb Natapov
2024-07-11 15:11:18 +03:00
parent 9a71543fd2
commit 87beebeed0
1 changed files with 7 additions and 12 deletions
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19
service/paxos/paxos_state.hh
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@@ -7,6 +7,7 @@
* SPDX-License-Identifier: (AGPL-3.0-or-later and Apache-2.0)
*/
#pragma once
#include "seastar/core/semaphore.hh"
#include "service/paxos/proposal.hh"
#include "log.hh"
#include "utils/digest_algorithm.hh"
@@ -31,6 +32,7 @@ private:
class key_lock_map {
using semaphore = basic_semaphore<semaphore_default_exception_factory, clock_type>;
using semaphore_units = semaphore_units<semaphore_default_exception_factory, clock_type>;
using map = std::unordered_map<dht::token, semaphore>;
semaphore& get_semaphore_for_key(const dht::token& key);
@@ -46,22 +48,15 @@ private:
key_lock_map& _map;
dht::token _key;
clock_type::time_point _timeout;
bool _locked = false;
key_lock_map::semaphore_units _units;
public:
future<> lock() {
auto f = _map.get_semaphore_for_key(_key).wait(_timeout, 1);
_locked = true;
return f;
future<> lock () {
return get_units(_map.get_semaphore_for_key(_key), 1, _timeout).then([this] (auto&& u) { _units = std::move(u); });
}
guard(key_lock_map& map, const dht::token& key, clock_type::time_point timeout) : _map(map), _key(key), _timeout(timeout) {};
guard(guard&& o) noexcept : _map(o._map), _key(std::move(o._key)), _timeout(o._timeout), _locked(o._locked) {
o._locked = false;
}
guard(guard&& o) = default;
~guard() {
if (_locked) {
_map.get_semaphore_for_key(_key).signal(1);
_map.release_semaphore_for_key(_key);
}
_map.release_semaphore_for_key(_key);
}
};