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author | Nat Goodspeed <nat@lindenlab.com> | 2024-06-14 12:16:12 -0400 |
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committer | Nat Goodspeed <nat@lindenlab.com> | 2024-06-14 12:16:12 -0400 |
commit | f7137765438f149cbae6f3b18da45dce75a25336 (patch) | |
tree | a93605eb2f22f97477ee418a1de04d9821713f07 /indra/newview/scripts/lua/require/fiber.lua | |
parent | dc91db0b85c5db1c20dccebd64c98419e371a29f (diff) |
Move Lua modules for 'require' to indra/newview/scripts/lua/require.
Make viewer_manifest.py copy them into the viewer install image.
Make the require() function look for them there.
Diffstat (limited to 'indra/newview/scripts/lua/require/fiber.lua')
-rw-r--r-- | indra/newview/scripts/lua/require/fiber.lua | 340 |
1 files changed, 340 insertions, 0 deletions
diff --git a/indra/newview/scripts/lua/require/fiber.lua b/indra/newview/scripts/lua/require/fiber.lua new file mode 100644 index 0000000000..cae27b936b --- /dev/null +++ b/indra/newview/scripts/lua/require/fiber.lua @@ -0,0 +1,340 @@ +-- Organize Lua coroutines into fibers. + +-- In this usage, the difference between coroutines and fibers is that fibers +-- have a scheduler. Yielding a fiber means allowing other fibers, plural, to +-- run: it's more than just returning control to the specific Lua thread that +-- resumed the running coroutine. + +-- fiber.launch() creates a new fiber ready to run. +-- fiber.status() reports (augmented) status of the passed fiber: instead of +-- 'suspended', it returns either 'ready' or 'waiting' +-- fiber.yield() allows other fibers to run, but leaves the calling fiber +-- ready to run. +-- fiber.wait() marks the running fiber not ready, and resumes other fibers. +-- fiber.wake() marks the designated suspended fiber ready to run, but does +-- not yet resume it. +-- fiber.run() runs all current fibers until all have terminated (successfully +-- or with an error). + +local printf = require 'printf' +local function dbg(...) end +-- local dbg = printf +local coro = require 'coro' + +local fiber = {} + +-- The tables in which we track fibers must have weak keys so dead fibers +-- can be garbage-collected. +local weak_values = {__mode='v'} +local weak_keys = {__mode='k'} + +-- Track each current fiber as being either ready to run or not ready +-- (waiting). wait() moves the running fiber from ready to waiting; wake() +-- moves the designated fiber from waiting back to ready. +-- The ready table is used as a list so yield() can go round robin. +local ready = setmetatable({'main'}, weak_keys) +-- The waiting table is used as a set because order doesn't matter. +local waiting = setmetatable({}, weak_keys) + +-- Every fiber has a name, for diagnostic purposes. Names must be unique. +-- A colliding name will be suffixed with an integer. +-- Predefine 'main' with our marker so nobody else claims that name. +local names = setmetatable({main='main'}, weak_keys) +local byname = setmetatable({main='main'}, weak_values) +-- each colliding name has its own distinct suffix counter +local suffix = {} + +-- Specify a nullary idle() callback to be called whenever there are no ready +-- fibers but there are waiting fibers. The idle() callback is responsible for +-- changing zero or more waiting fibers to ready fibers by calling +-- fiber.wake(), although a given call may leave them all still waiting. +-- When there are no ready fibers, it's a good idea for the idle() function to +-- return control to a higher-level execution agent. Simply returning without +-- changing any fiber's status will spin the CPU. +-- The idle() callback can return non-nil to exit fiber.run() with that value. +function fiber._idle() + error('fiber.yield(): you must first call set_idle(nullary idle() function)') +end + +function fiber.set_idle(func) + fiber._idle = func +end + +-- Launch a new Lua fiber, ready to run. +function fiber.launch(name, func, ...) + local args = table.pack(...) + local co = coroutine.create(function() func(table.unpack(args)) end) + -- a new fiber is ready to run + table.insert(ready, co) + local namekey = name + while byname[namekey] do + if not suffix[name] then + suffix[name] = 1 + end + suffix[name] += 1 + namekey = name .. tostring(suffix[name]) + end + -- found a namekey not yet in byname: set it + byname[namekey] = co + -- and remember it as this fiber's name + names[co] = namekey +-- dbg('launch(%s)', namekey) +-- dbg('byname[%s] = %s', namekey, tostring(byname[namekey])) +-- dbg('names[%s] = %s', tostring(co), names[co]) +-- dbg('ready[-1] = %s', tostring(ready[#ready])) +end + +-- for debugging +function format_all() + output = {} + table.insert(output, 'Ready fibers:' .. if next(ready) then '' else ' none') + for _, co in pairs(ready) do + table.insert(output, string.format(' %s: %s', fiber.get_name(co), fiber.status(co))) + end + table.insert(output, 'Waiting fibers:' .. if next(waiting) then '' else ' none') + for co in pairs(waiting) do + table.insert(output, string.format(' %s: %s', fiber.get_name(co), fiber.status(co))) + end + return table.concat(output, '\n') +end + +function fiber.print_all() + print(format_all()) +end + +-- return either the running coroutine or, if called from the main thread, +-- 'main' +function fiber.running() + return coroutine.running() or 'main' +end + +-- Query a fiber's name (nil for the running fiber) +function fiber.get_name(co) + return names[co or fiber.running()] or 'unknown' +end + +-- Query status of the passed fiber +function fiber.status(co) + local running = coroutine.running() + if (not co) or co == running then + -- silly to ask the status of the running fiber: it's 'running' + return 'running' + end + if co ~= 'main' then + -- for any coroutine but main, consult coroutine.status() + local status = coroutine.status(co) + if status ~= 'suspended' then + return status + end + -- here co is suspended, answer needs further refinement + else + -- co == 'main' + if not running then + -- asking about 'main' from the main fiber + return 'running' + end + -- asking about 'main' from some other fiber, so presumably main is suspended + end + -- here we know co is suspended -- but is it ready to run? + if waiting[co] then + return 'waiting' + end + -- not waiting should imply ready: sanity check + if table.find(ready, co) then + return 'ready' + end + -- Calls within yield() between popping the next ready fiber and + -- re-appending it to the list are in this state. Once we're done + -- debugging yield(), we could reinstate either of the below. +-- error(string.format('fiber.status(%s) is stumped', fiber.get_name(co))) +-- print(string.format('*** fiber.status(%s) is stumped', fiber.get_name(co))) + return '(unknown)' +end + +-- change the running fiber's status to waiting +local function set_waiting() + -- if called from the main fiber, inject a 'main' marker into the list + co = fiber.running() + -- delete from ready list + local i = table.find(ready, co) + if i then + table.remove(ready, i) + end + -- add to waiting list + waiting[co] = true +end + +-- Suspend the current fiber until some other fiber calls fiber.wake() on it +function fiber.wait() + dbg('Fiber %q waiting', fiber.get_name()) + set_waiting() + -- now yield to other fibers + fiber.yield() +end + +-- Mark a suspended fiber as being ready to run +function fiber.wake(co) + if not waiting[co] then + error(string.format('fiber.wake(%s) but status=%s, ready=%s, waiting=%s', + names[co], fiber.status(co), ready[co], waiting[co])) + end + -- delete from waiting list + waiting[co] = nil + -- add to end of ready list + table.insert(ready, co) + dbg('Fiber %q ready', fiber.get_name(co)) + -- but don't yet resume it: that happens next time we reach yield() +end + +-- pop and return the next not-dead fiber in the ready list, or nil if none remain +local function live_ready_iter() + -- don't write: + -- for co in table.remove, ready, 1 + -- because it would keep passing a new second parameter! + for co in function() return table.remove(ready, 1) end do + dbg('%s live_ready_iter() sees %s, status %s', + fiber.get_name(), fiber.get_name(co), fiber.status(co)) + -- keep removing the head entry until we find one that's not dead, + -- discarding any dead coroutines along the way + if co == 'main' or coroutine.status(co) ~= 'dead' then + dbg('%s live_ready_iter() returning %s', + fiber.get_name(), fiber.get_name(co)) + return co + end + end + dbg('%s live_ready_iter() returning nil', fiber.get_name()) + return nil +end + +-- prune the set of waiting fibers +local function prune_waiting() + for waiter in pairs(waiting) do + if waiter ~= 'main' and coroutine.status(waiter) == 'dead' then + waiting[waiter] = nil + end + end +end + +-- Run other ready fibers, leaving this one ready, returning after a cycle. +-- Returns: +-- * true, nil if there remain other live fibers, whether ready or waiting, +-- but it's our turn to run +-- * false, nil if this is the only remaining fiber +-- * nil, x if configured idle() callback returns non-nil x +local function scheduler() + dbg('scheduler():\n%s', format_all()) + -- scheduler() is asymmetric because Lua distinguishes the main thread + -- from other coroutines. The main thread can't yield; it can only resume + -- other coroutines. So although an arbitrary coroutine could resume still + -- other arbitrary coroutines, it could NOT resume the main thread because + -- the main thread can't yield. Therefore, scheduler() delegates its real + -- processing to the main thread. If called from a coroutine, pass control + -- back to the main thread. + if coroutine.running() then + -- this is a real coroutine, yield normally to main thread + coroutine.yield() + -- main certainly still exists + return true + end + + -- This is the main fiber: coroutine.yield() doesn't work. + -- Instead, resume each of the ready fibers. + -- Prune the set of waiting fibers after every time fiber business logic + -- runs (i.e. other fibers might have terminated or hit error), such as + -- here on entry. + prune_waiting() + local others, idle_stop + repeat + for co in live_ready_iter do + -- seize the opportunity to make sure the viewer isn't shutting down + LL.check_stop() + -- before we re-append co, is it the only remaining entry? + others = next(ready) + -- co is live, re-append it to the ready list + table.insert(ready, co) + if co == 'main' then + -- Since we know the caller is the main fiber, it's our turn. + -- Tell caller if there are other ready or waiting fibers. + return others or next(waiting) + end + -- not main, but some other ready coroutine: + -- use coro.resume() so we'll propagate any error encountered + coro.resume(co) + prune_waiting() + end + -- Here there are no ready fibers. Are there any waiting fibers? + if not next(waiting) then + return false + end + -- there are waiting fibers: call consumer's configured idle() function + idle_stop = fiber._idle() + if idle_stop ~= nil then + return nil, idle_stop + end + prune_waiting() + -- loop "forever", that is, until: + -- * main is ready, or + -- * there are neither ready fibers nor waiting fibers, or + -- * fiber._idle() returned non-nil + until false +end + +-- Let other fibers run. This is useful in either of two cases: +-- * fiber.wait() calls this to run other fibers while this one is waiting. +-- fiber.yield() (and therefore fiber.wait()) works from the main thread as +-- well as from explicitly-launched fibers, without the caller having to +-- care. +-- * A long-running fiber that doesn't often call fiber.wait() should sprinkle +-- in fiber.yield() calls to interleave processing on other fibers. +function fiber.yield() + -- The difference between this and fiber.run() is that fiber.yield() + -- assumes its caller has work to do. yield() returns to its caller as + -- soon as scheduler() pops this fiber from the ready list. fiber.run() + -- continues looping until all other fibers have terminated, or the + -- set_idle() callback tells it to stop. + local others, idle_done = scheduler() + -- scheduler() returns either if we're ready, or if idle_done ~= nil. + if idle_done ~= nil then + -- Returning normally from yield() means the caller can carry on with + -- its pending work. But in this case scheduler() returned because the + -- configured set_idle() function interrupted it -- not because we're + -- actually ready. Don't return normally. + error('fiber.set_idle() interrupted yield() with: ' .. tostring(idle_done)) + end + -- We're ready! Just return to caller. In this situation we don't care + -- whether there are other ready fibers. + dbg('fiber.yield() returning to %s (%sothers are ready)', + fiber.get_name(), ((not others) and "no " or "")) +end + +-- Run fibers until all but main have terminated: return nil. +-- Or until configured idle() callback returns x ~= nil: return x. +function fiber.run() + -- A fiber calling run() is not also doing other useful work. Remove the + -- calling fiber from the ready list. Otherwise yield() would keep seeing + -- that our caller is ready and return to us, instead of realizing that + -- all coroutines are waiting and call idle(). But don't say we're + -- waiting, either, because then when all other fibers have terminated + -- we'd call idle() forever waiting for something to make us ready again. + local i = table.find(ready, fiber.running()) + if i then + table.remove(ready, i) + end + local others, idle_done + repeat + dbg('%s calling fiber.run() calling scheduler()', fiber.get_name()) + others, idle_done = scheduler() + dbg("%s fiber.run()'s scheduler() returned %s, %s", fiber.get_name(), + tostring(others), tostring(idle_done)) + until (not others) + dbg('%s fiber.run() done', fiber.get_name()) + -- For whatever it's worth, put our own fiber back in the ready list. + table.insert(ready, fiber.running()) + -- Once there are no more waiting fibers, and the only ready fiber is + -- us, return to caller. All previously-launched fibers are done. Possibly + -- the chunk is done, or the chunk may decide to launch a new batch of + -- fibers. + return idle_done +end + +return fiber |