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c12f976389
audit_syslog_storage_helper::syslog_send_helper uses Seastar's net::datagram_channel to write to syslog device (usually /dev/log). However, datagram_channel.send() is not fiber-safe (ref seastar#2690), so unserialized use of send() results in packets overwriting its state. This, in turn, causes a corruption of audit logs, as well as assertion failures. To workaround the problem, a new semaphore is introduced in audit_syslog_storage_helper. As storage_helper is a member of sharded audit service, the semaphore allows for one datagram_channel.send() on each shard. Each audit_syslog_storage_helper stores its own datagram_channel, therefore concurrent sends to datagram_channel are eliminated. This change: - Introduce semaphore with count=1 in audit_syslog_storage_helper. - Added 1 hour timeout to the semaphore, so semaphore stalls are failed just as all other syslog auditing failures. Fixes: scylladb#22973