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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
/*
* Ceph - scalable distributed file system
*
* Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
*
* This is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 2.1, as published by the Free Software
* Foundation. See file COPYING.
*
*/
#ifndef CEPH_FINISHER_H
#define CEPH_FINISHER_H
#include "include/Context.h"
#include "include/common_fwd.h"
#include "common/Thread.h"
#include "common/ceph_mutex.h"
#include "common/Cond.h"
/// Finisher queue length performance counter ID.
enum {
l_finisher_first = 997082,
l_finisher_queue_len,
l_finisher_complete_lat,
l_finisher_last
};
/** @brief Asynchronous cleanup class.
* Finisher asynchronously completes Contexts, which are simple classes
* representing callbacks, in a dedicated worker thread. Enqueuing
* contexts to complete is thread-safe.
*/
class Finisher {
CephContext *const cct;
ceph::mutex finisher_lock; ///< Protects access to queues and finisher_running.
ceph::condition_variable finisher_cond; ///< Signaled when there is something to process.
ceph::condition_variable finisher_empty_cond; ///< Signaled when the finisher has nothing more to process.
bool finisher_stop = false; ///< Set when the finisher should stop.
bool finisher_running = false; ///< True when the finisher is currently executing contexts.
bool finisher_empty_wait = false; ///< True mean someone wait finisher empty.
/// Queue for contexts for which complete(0) will be called.
std::vector<std::pair<Context*,int>> finisher_queue;
std::vector<std::pair<Context*,int>> in_progress_queue;
const std::string thread_name;
/// Performance counter for the finisher's queue length.
/// Only active for named finishers.
PerfCounters *logger = nullptr;
void *finisher_thread_entry();
struct FinisherThread : public Thread {
Finisher *fin;
explicit FinisherThread(Finisher *f) : fin(f) {}
void* entry() override { return fin->finisher_thread_entry(); }
} finisher_thread;
public:
/// Add a context to complete, optionally specifying a parameter for the complete function.
void queue(Context *c, int r = 0) {
{
const std::lock_guard l{finisher_lock};
const bool should_notify = finisher_queue.empty() && !finisher_running;
finisher_queue.push_back(std::make_pair(c, r));
if (should_notify) {
finisher_cond.notify_one();
}
}
if (logger)
logger->inc(l_finisher_queue_len);
}
// TODO use C++20 concept checks instead of SFINAE
template<typename T>
auto queue(T &ls) -> decltype(std::distance(ls.begin(), ls.end()), void()) {
{
const std::lock_guard l{finisher_lock};
const bool should_notify = finisher_queue.empty() && !finisher_running;
for (Context *i : ls) {
finisher_queue.push_back(std::make_pair(i, 0));
}
if (should_notify) {
finisher_cond.notify_one();
}
}
if (logger)
logger->inc(l_finisher_queue_len, ls.size());
ls.clear();
}
/// Start the worker thread.
void start();
/** @brief Stop the worker thread.
*
* Does not wait until all outstanding contexts are completed.
* To ensure that everything finishes, you should first shut down
* all sources that can add contexts to this finisher and call
* wait_for_empty() before calling stop(). */
void stop();
/** @brief Blocks until the finisher has nothing left to process.
* This function will also return when a concurrent call to stop()
* finishes, but this class should never be used in this way. */
void wait_for_empty();
bool is_empty();
std::string_view get_thread_name() const noexcept {
return thread_name;
}
/// Construct an anonymous Finisher.
/// Anonymous finishers do not log their queue length.
explicit Finisher(CephContext *cct_);
/// Construct a named Finisher that logs its queue length.
Finisher(CephContext *cct_, std::string_view name, std::string &&tn);
~Finisher();
};
/// Context that is completed asynchronously on the supplied finisher.
class C_OnFinisher : public Context {
Context *con;
Finisher *fin;
public:
C_OnFinisher(Context *c, Finisher *f) : con(c), fin(f) {
ceph_assert(fin != NULL);
ceph_assert(con != NULL);
}
~C_OnFinisher() override {
if (con != nullptr) {
delete con;
con = nullptr;
}
}
void finish(int r) override {
fin->queue(con, r);
con = nullptr;
}
};
class ContextQueue {
std::list<Context *> q;
std::mutex q_mutex;
ceph::mutex& mutex;
ceph::condition_variable& cond;
std::atomic_bool q_empty = true;
public:
ContextQueue(ceph::mutex& mut,
ceph::condition_variable& con)
: mutex(mut), cond(con) {}
void queue(std::list<Context *>& ls) {
bool was_empty = false;
{
std::scoped_lock l(q_mutex);
if (q.empty()) {
q.swap(ls);
was_empty = true;
} else {
q.insert(q.end(), ls.begin(), ls.end());
}
q_empty = q.empty();
}
if (was_empty) {
std::scoped_lock l{mutex};
cond.notify_all();
}
ls.clear();
}
void move_to(std::list<Context *>& ls) {
ls.clear();
std::scoped_lock l(q_mutex);
if (!q.empty()) {
q.swap(ls);
}
q_empty = true;
}
bool empty() {
return q_empty;
}
};
#endif
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