118 lines
4.2 KiB
C++
118 lines
4.2 KiB
C++
/*
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Copyright (c) 2003-2016, Arvid Norberg
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the distribution.
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* Neither the name of the author nor the names of its
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef TORRENT_DISK_JOB_FENCE_HPP_INCLUDE
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#define TORRENT_DISK_JOB_FENCE_HPP_INCLUDE
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#include "libtorrent/config.hpp"
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#include "libtorrent/tailqueue.hpp"
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#include <atomic>
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#include <mutex>
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namespace libtorrent {
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struct disk_io_job;
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struct counters;
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namespace aux {
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// implements the disk I/O job fence used by the storage_interface
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// to provide to the disk thread. Whenever a disk job needs
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// exclusive access to the storage for that torrent, it raises
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// the fence, blocking all new jobs, until there are no longer
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// any outstanding jobs on the torrent, then the fence is lowered
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// and it can be performed, along with the backlog of jobs that
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// accrued while the fence was up
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struct TORRENT_EXPORT disk_job_fence
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{
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disk_job_fence();
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~disk_job_fence()
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{
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TORRENT_ASSERT(int(m_outstanding_jobs) == 0);
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TORRENT_ASSERT(m_blocked_jobs.size() == 0);
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}
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// returns one of the fence_* enums.
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// if there are no outstanding jobs on the
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// storage, fence_post_fence is returned, the flush job is expected
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// to be discarded by the caller.
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// fence_post_flush is returned if the fence job was blocked and queued,
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// but the flush job should be posted (i.e. put on the job queue)
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// fence_post_none if both the fence and the flush jobs were queued.
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enum { fence_post_fence = 0, fence_post_flush = 1, fence_post_none = 2 };
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int raise_fence(disk_io_job* fence_job, disk_io_job* flush_job
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, counters& cnt);
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bool has_fence() const;
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// called whenever a job completes and is posted back to the
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// main network thread. the tailqueue of jobs will have the
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// backed-up jobs prepended to it in case this resulted in the
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// fence being lowered.
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int job_complete(disk_io_job* j, tailqueue<disk_io_job>& job_queue);
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int num_outstanding_jobs() const { return m_outstanding_jobs; }
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// if there is a fence up, returns true and adds the job
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// to the queue of blocked jobs
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bool is_blocked(disk_io_job* j);
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// the number of blocked jobs
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int num_blocked() const;
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private:
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// when > 0, this storage is blocked for new async
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// operations until all outstanding jobs have completed.
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// at that point, the m_blocked_jobs are issued
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// the count is the number of fence job currently in the queue
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int m_has_fence = 0;
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// when there's a fence up, jobs are queued up in here
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// until the fence is lowered
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tailqueue<disk_io_job> m_blocked_jobs;
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// the number of disk_io_job objects there are, belonging
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// to this torrent, currently pending, hanging off of
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// cached_piece_entry objects. This is used to determine
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// when the fence can be lowered
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std::atomic<int> m_outstanding_jobs{0};
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// must be held when accessing m_has_fence and
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// m_blocked_jobs
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mutable std::mutex m_mutex;
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};
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}}
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#endif
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