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RequestServer: Avoid race condition between cached request end/start

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Prior to this commit, it was possible to get a socket stuck in a state
with enqueued entries, waiting for a nonexistent request to finish.
This state could be entered by issuing a request immediately after the
completion of another one, and before deferred_invoke execution in the
event loop.

This commit closes this hole by making sure the socket is never in a
state where it can queue requests without an active job.
This commit is contained in:
Ali Mohammad Pur 2023-12-15 06:34:34 +03:30 • committed by Andreas Kling
parent 47b6030347
commit 89877b3f40
2 changed files with 17 additions and 9 deletions
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10
Userland/Services/RequestServer/ConnectionCache.cpp
View file

@ -38,9 +38,15 @@ void request_did_finish(URL const& url, Core::Socket const* socket)
auto& connection = *connection_it;
if (connection->request_queue.is_empty()) {
Core::deferred_invoke([&connection, &cache_entry = *it->value, key = it->key, &cache] {
connection->socket->set_notifications_enabled(false);
// Immediately mark the connection as finished, as new jobs will never be run if they are queued
// before the deferred_invoke() below runs otherwise.
connection->has_started = false;
connection->socket->set_notifications_enabled(false);
Core::deferred_invoke([&connection, &cache_entry = *it->value, key = it->key, &cache] {
if (connection->has_started)
return;
connection->current_url = {};
connection->job_data = {};
connection->removal_timer->on_timeout = [ptr = connection.ptr(), &cache_entry, key = move(key), &cache]() mutable {

2
Userland/Services/RequestServer/ConnectionCache.h
View file

@ -241,6 +241,7 @@ decltype(auto) get_or_create_connection(auto& cache, URL const& url, auto& job,
return ReturnType { nullptr };
}
dbgln_if(REQUESTSERVER_DEBUG, "Immediately start request for url {} in {} - {}", url, &connection, connection.socket);
Core::deferred_invoke([&connection, url, &job] {
connection.has_started = true;
connection.removal_timer->stop();
connection.timer.start();
@ -248,6 +249,7 @@ decltype(auto) get_or_create_connection(auto& cache, URL const& url, auto& job,
connection.job_data = decltype(connection.job_data)::create(job);
connection.socket->set_notifications_enabled(true);
connection.job_data.start(*connection.socket);
});
} else {
dbgln_if(REQUESTSERVER_DEBUG, "Enqueue request for URL {} in {} - {}", url, &connection, connection.socket);
connection.request_queue.append(decltype(connection.job_data)::create(job));