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https://github.com/jart/cosmopolitan.git
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7822917fc2
You can now do things like implement mutexes using futexes in your redbean lua code. This provides the fastest possible inter-process communication for your production systems when SQLite alone as ipc or things like pipes aren't sufficient.
76 lines
2 KiB
Lua
76 lines
2 KiB
Lua
-- Copyright 2022 Justine Alexandra Roberts Tunney
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--
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-- Permission to use, copy, modify, and/or distribute this software for
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-- any purpose with or without fee is hereby granted, provided that the
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-- above copyright notice and this permission notice appear in all copies.
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--
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-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
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-- WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
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-- WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
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-- AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
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-- DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
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-- PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
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-- TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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-- PERFORMANCE OF THIS SOFTWARE.
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assert(unix.pledge("stdio proc"))
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words = 2
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processes = 8
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iterations = 10000
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mem = unix.mapshared(words * 8)
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--------------------------------------------------------------------------------
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-- let's use atomics to implement a spin lock in lua
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LOCK = 0 -- word index of our lock
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COUNTER = 1 -- word index of our number
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function Lock()
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while mem:xchg(LOCK, 1) == 1 do
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end
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end
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function Unlock()
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mem:store(LOCK, 0)
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end
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function Worker()
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local x
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for i = 1,iterations do
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Lock()
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x = mem:load(COUNTER)
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x = x + 1
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mem:store(COUNTER, x)
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Unlock()
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end
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end
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mem:store(LOCK, 0)
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mem:store(COUNTER, 0)
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for i = 1,processes do
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pid = assert(unix.fork())
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if pid == 0 then
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Worker()
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unix.exit(0)
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end
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end
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while true do
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rc, ws = unix.wait(0)
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if not rc then
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assert(ws:errno() == unix.ECHILD)
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break
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end
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if unix.WIFEXITED(ws) then
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if unix.WEXITSTATUS(ws) ~= 0 then
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print('process %d exited with %s' % {rc, unix.WEXITSTATUS(ws)})
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unix.exit(1)
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end
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else
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print('process %d terminated with %s' % {rc, unix.WTERMSIG(ws)})
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unix.exit(1)
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end
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end
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assert(mem:load(COUNTER) == processes * iterations)
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