X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fnotification-thread.hpp;fp=src%2Fbin%2Flttng-sessiond%2Fnotification-thread.hpp;h=3444af9c041c24e5570390764bd23a46fd7eb20b;hp=0000000000000000000000000000000000000000;hb=c9e313bc594f40a86eed237dce222c0fc99c957f;hpb=4878de5c7deb512bbdac4fdfc498907efa06fb7c diff --git a/src/bin/lttng-sessiond/notification-thread.hpp b/src/bin/lttng-sessiond/notification-thread.hpp new file mode 100644 index 000000000..3444af9c0 --- /dev/null +++ b/src/bin/lttng-sessiond/notification-thread.hpp @@ -0,0 +1,325 @@ +/* + * Copyright (C) 2017 Jérémie Galarneau + * + * SPDX-License-Identifier: GPL-2.0-only + * + */ + +#ifndef NOTIFICATION_THREAD_H +#define NOTIFICATION_THREAD_H + +#include "action-executor.hpp" +#include "thread.hpp" +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +typedef uint64_t notification_client_id; + +/* + * The notification thread holds no ownership of the tracer event source pipe + * file descriptor. The tracer management logic must remove the event source + * from the notification thread (see external commands) before releasing + * this file descriptor. + */ +struct notification_event_tracer_event_source_element { + int fd; + /* + * A tracer event source can be removed from the notification thread's + * poll set before the end of its lifetime (for instance, when an error + * or hang-up is detected on its file descriptor). This is done to + * allow the notification thread to ignore follow-up events on this + * file descriptors. + * + * Under such circumstances, the notification thread still expects + * the normal clean-up to occur through the 'REMOVE_TRACER_EVENT_SOURCE' + * command. + */ + bool is_fd_in_poll_set; + enum lttng_domain_type domain; + struct cds_list_head node; +}; + +struct notification_trigger_tokens_ht_element { + uint64_t token; + /* Weak reference to the trigger. */ + struct lttng_trigger *trigger; + struct cds_lfht_node node; + /* call_rcu delayed reclaim. */ + struct rcu_head rcu_node; +}; + +struct notification_thread_handle { + /* + * Queue of struct notification command. + * event_pipe must be WRITE(2) to signal that a new command + * has been enqueued. + */ + struct { + struct lttng_pipe *event_pipe; + struct cds_list_head list; + pthread_mutex_t lock; + } cmd_queue; + /* + * Read side of pipes used to receive channel status info collected + * by the various consumer daemons. + */ + struct { + int ust32_consumer; + int ust64_consumer; + int kernel_consumer; + } channel_monitoring_pipes; + /* Used to wait for the launch of the notification thread. */ + sem_t ready; +}; + +/** + * This thread maintains an internal state associating clients and triggers. + * + * In order to speed-up and simplify queries, hash tables providing the + * following associations are maintained: + * + * - client_socket_ht: associate a client's socket (fd) to its + * "struct notification_client". + * This hash table owns the "struct notification_client" which must + * thus be disposed-of on removal from the hash table. + * + * - client_id_ht: associate a client's id to its "struct notification_client" + * This hash table holds a _weak_ reference to the + * "struct notification_client". + * + * - channel_triggers_ht: + * associates a channel key to a list of + * struct lttng_trigger_list_nodes. The triggers in this list are + * those that have conditions that apply to a particular channel. + * A channel entry is only created when a channel is added; the + * list of triggers applying to such a channel is built at that + * moment. + * This hash table owns the list, but not the triggers themselves. + * + * - session_triggers_ht: + * associates a session name to a list of + * struct lttng_trigger_list_nodes. The triggers in this list are + * those that have conditions that apply to a particular session. + * A session entry is only created when a session is created; the + * list of triggers applying to this new session is built at that + * moment. This happens at the time of creation of a session_info. + * Likewise, the list is destroyed at the time of the session_info's + * destruction. + * + * - channel_state_ht: + * associates a pair (channel key, channel domain) to its last + * sampled state received from the consumer daemon + * (struct channel_state). + * This previous sample is kept to implement edge-triggered + * conditions as we need to detect the state transitions. + * This hash table owns the channel state. + * + * - notification_trigger_clients_ht: + * associates notification-emitting triggers to clients + * (struct notification_client_list) subscribed to those + * conditions. + * The condition's hash and match functions are used directly since + * all triggers in this hash table have the "notify" action. + * This hash table holds no ownership. + * + * - channels_ht: + * associates a channel_key to a struct channel_info. The hash table + * holds the ownership of the struct channel_info. + * + * - sessions_ht: + * associates a session_name (hash) to a struct session_info. The + * hash table holds no ownership of the struct session_info; + * the session_info structure is owned by the session's various + * channels through their struct channel_info (ref-counting is used). + * + * - triggers_ht: + * associates a trigger to a struct lttng_trigger_ht_element. + * The hash table holds the ownership of the + * lttng_trigger_ht_elements along with the triggers themselves. + * - triggers_by_name_uid_ht: + * associates a trigger (name, uid) tuple to + * a struct lttng_trigger_ht_element. + * The hash table does not hold any ownership and is used strictly + * for lookup on registration. + * - tracer_event_sources_list: + * A list of tracer event source (read side fd) of type +* struct notification_event_tracer_event_source_element. +* + * + * The thread reacts to the following internal events: + * 1) creation of a tracing channel, + * 2) destruction of a tracing channel, + * 3) registration of a trigger, + * 4) unregistration of a trigger, + * 5) reception of a channel monitor sample from the consumer daemon, + * 6) Session rotation ongoing, + * 7) Session rotation completed, + * 8) registration of a tracer event source, + * 9) unregistration of a tracer event source, + * + * Events specific to notification-emitting triggers: + * 9) connection of a notification client, + * 10) disconnection of a notification client, + * 11) subscription of a client to a conditions' notifications, + * 12) unsubscription of a client from a conditions' notifications, + * + * + * 1) Creation of a tracing channel + * - notification_trigger_clients_ht is traversed to identify + * triggers which apply to this new channel, + * - triggers identified are added to the channel_triggers_ht. + * - add channel to channels_ht + * - if it is the first channel of a session, a session_info is created and + * added to the sessions_ht. A list of the triggers associated with that + * session is built, and it is added to session_triggers_ht. + * + * 2) Destruction of a tracing channel + * - remove entry from channel_triggers_ht, releasing the list wrapper and + * elements, + * - remove entry from the channel_state_ht. + * - remove channel from channels_ht + * - if it was the last known channel of a session, the session_info + * structure is torndown, which in return destroys the list of triggers + * applying to that session. + * + * 3) Registration of a trigger + * - if the trigger's action is of type "notify", + * - traverse the list of conditions of every client to build a list of + * clients which have to be notified when this trigger's condition is met, + * - add list of clients (even if it is empty) to the + * notification_trigger_clients_ht, + * - add trigger to channel_triggers_ht (if applicable), + * - add trigger to session_triggers_ht (if applicable), + * - add trigger to triggers_by_name_uid_ht + * - add trigger to triggers_ht + * - evaluate the trigger's condition right away to react if that condition + * is true from the beginning. + * + * 4) Unregistration of a trigger + * - if the trigger's action is of type "notify", + * - remove the trigger from the notification_trigger_clients_ht, + * - remove trigger from channel_triggers_ht (if applicable), + * - remove trigger from session_triggers_ht (if applicable), + * - remove trigger from triggers_by_name_uid_ht + * - remove trigger from triggers_ht + * + * 5) Reception of a channel monitor sample from the consumer daemon + * - evaluate the conditions associated with the triggers found in + * the channel_triggers_ht, + * - if a condition evaluates to "true" and the condition is of type + * "notify", query the notification_trigger_clients_ht and send + * a notification to the clients. + * + * 6) Session rotation ongoing + * + * 7) Session rotation completed + * + * 8) Registration of a tracer event source + * - Add the tracer event source of the application to + * tracer_event_sources_list, + * - Add the trace event source to the pollset. + * + * 8) Unregistration of a tracer event source + * - Remove the tracer event source of the application from + * tracer_event_sources_list, + * - Remove the trace event source from the pollset. + * + * 10) Connection of a client + * - add client socket to the client_socket_ht, + * - add client socket to the client_id_ht. + * + * 11) Disconnection of a client + * - remove client socket from the client_id_ht, + * - remove client socket from the client_socket_ht, + * - traverse all conditions to which the client is subscribed and remove + * the client from the notification_trigger_clients_ht. + * + * 12) Subscription of a client to a condition's notifications + * - Add the condition to the client's list of subscribed conditions, + * - Look-up notification_trigger_clients_ht and add the client to + * list of clients. + * - Evaluate the condition for the client that subscribed if the trigger + * was already registered. + * + * 13) Unsubscription of a client to a condition's notifications + * - Remove the condition from the client's list of subscribed conditions, + * - Look-up notification_trigger_clients_ht and remove the client + * from the list of clients. + */ +struct notification_thread_state { + int notification_channel_socket; + struct lttng_poll_event events; + struct cds_lfht *client_socket_ht; + struct cds_lfht *client_id_ht; + struct cds_lfht *channel_triggers_ht; + struct cds_lfht *session_triggers_ht; + struct cds_lfht *channel_state_ht; + struct cds_lfht *notification_trigger_clients_ht; + struct cds_lfht *channels_ht; + struct cds_lfht *sessions_ht; + struct cds_lfht *triggers_ht; + struct cds_lfht *triggers_by_name_uid_ht; + struct cds_lfht *trigger_tokens_ht; + struct { + uint64_t next_tracer_token; + uint64_t name_offset; + } trigger_id; + /* + * Read side of the pipes used to receive tracer events. As their name + * implies, tracer event source activity originate from either + * registered applications (user space tracer) or from the kernel + * tracer. + * + * The list is not protected by a lock since add and remove operations + * are currently done only by the notification thread through in + * response to blocking commands. + */ + struct cds_list_head tracer_event_sources_list; + notification_client_id next_notification_client_id; + struct action_executor *executor; + + /* + * Indicates the thread to break for the poll event processing loop and + * call _poll_wait() again. + * + * This is necessary because some events on one fd might trigger the + * consumption of another fd. + * For example, a single _poll_wait() call can return notification + * thread commands and events from the tracer event source (event + * notifier). + * Picture a scenario where we receive two events: + * the first one is a _REMOVE_TRACER_EVENT_SOURCE command, and + * the second is an POLLIN on the tracer event source fd. + * + * The _REMOVE_TRACER_EVENT_SOURCE will read all the data of the + * removed tracer event source. + * + * The second event is now invalid has we consumed all the data for + * which we received the POLLIN. + * + * For this reason, we need to break for the event processing loop and + * call _poll_wait() again to get a clean view of the activity on the + * fds. + */ + bool restart_poll; +}; + +/* notification_thread_data takes ownership of the channel monitor pipes. */ +struct notification_thread_handle *notification_thread_handle_create( + struct lttng_pipe *ust32_channel_monitor_pipe, + struct lttng_pipe *ust64_channel_monitor_pipe, + struct lttng_pipe *kernel_channel_monitor_pipe); +void notification_thread_handle_destroy( + struct notification_thread_handle *handle); +struct lttng_thread *launch_notification_thread( + struct notification_thread_handle *handle); + +#endif /* NOTIFICATION_THREAD_H */