mirror of
https://github.com/matrix-construct/construct
synced 2024-10-31 10:58:54 +01:00
139 lines
4.1 KiB
C++
139 lines
4.1 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#pragma once
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#define HAVE_IRCD_CTX_THIS_CTX_H
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/// Interface to the currently running context
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namespace ircd::ctx { inline namespace this_ctx
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{
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/// ios descriptor used by yield().
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extern ios::descriptor courtesy_yield_desc;
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struct ctx &cur() noexcept; ///< Assumptional reference to *current
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const uint64_t &id() noexcept; // Unique ID for cur ctx
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string_view name() noexcept; // Optional label for cur ctx
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ulong cycles() noexcept; // misc profiling related
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bool interruption_requested() noexcept; // interruption(cur())
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void interruption_point(); // throws if interruption_requested()
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bool interruptible() noexcept;
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void interruptible(const bool &, std::nothrow_t) noexcept;
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void interruptible(const bool &);
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void yield(); // Allow other contexts to run before returning.
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}}
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namespace ircd::ctx
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{
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/// Points to the currently running context or null for main stack (do not modify)
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extern thread_local ctx *current;
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}
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namespace ircd
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{
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namespace this_ctx = ctx::this_ctx;
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}
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/// Post the currently running context to the event queue and then suspend to
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/// allow other contexts in the queue to run.
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///
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/// Until we have our own queue the ios queue makes no guarantees if the queue
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/// is FIFO or LIFO etc :-/ It is generally bad practice to use this function,
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/// as one should make the effort to devise a specific cooperative strategy for
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/// how context switching occurs rather than this coarse/brute technique.
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inline void
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ircd::ctx::this_ctx::yield()
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{
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ios::dispatch
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{
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courtesy_yield_desc, ios::defer, ios::yield
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};
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}
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inline void
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ircd::ctx::this_ctx::interruptible(const bool &b,
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std::nothrow_t)
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noexcept
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{
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interruptible(cur(), b);
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}
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inline bool
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ircd::ctx::this_ctx::interruptible()
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noexcept
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{
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return interruptible(cur());
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}
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/// Throws interrupted if the currently running context was interrupted
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/// and clears the interrupt flag.
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inline void
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ircd::ctx::this_ctx::interruptible(const bool &b)
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{
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const bool theirs
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{
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interruptible(cur())
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};
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if(unlikely(theirs && !b && interruption_requested()))
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interruption_point();
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interruptible(cur(), b);
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if(unlikely(!theirs && b && interruption_requested()))
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interruption_point();
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}
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/// Returns true if the currently running context was interrupted and clears
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/// the interrupt flag.
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inline bool
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ircd::ctx::this_ctx::interruption_requested()
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noexcept
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{
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return interruption(cur()) || termination(cur());
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}
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/// Calculate the current TSC (reference cycle count) accumulated for this
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/// context only. This is done by first calculating a cycle count for the
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/// current slice/epoch (see: ctx/prof.h) which is where the RDTSC sample
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/// occurs. This count is added to an accumulator value saved in the ctx
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/// structure. The accumulator value is updated at the end of each execution
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/// slice, thus giving us the cycle count for this ctx only, up to this point.
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extern inline ulong
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__attribute__((flatten, always_inline, gnu_inline, artificial))
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ircd::ctx::this_ctx::cycles()
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noexcept
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{
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const auto slice(prof::cur_slice_cycles());
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const auto accumulated(cycles(cur()));
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return accumulated + slice;
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}
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/// View the name of the currently running context, or "*" if no context is
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/// currently running.
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inline ircd::string_view
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ircd::ctx::this_ctx::name()
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noexcept
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{
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return current? name(cur()) : "*"_sv;
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}
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/// Reference to the currently running context. Call if you expect to be in a
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/// context. Otherwise use the ctx::current pointer.
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inline ircd::ctx::ctx &
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__attribute__((always_inline))
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ircd::ctx::this_ctx::cur()
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noexcept
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{
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assert(current);
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return *current;
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}
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