//
// Cforall Version 1.0.0 Copyright (C) 2022 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// away_fair.cfa -- Test that spinning doesn't cause submissions to get stuck.
//                  This test should work without io_uring but isn't very useful without
//
// Author           : Thierry Delisle
// Created On       : Wed Mar 2 12:56:51 2022
// Last Modified By :
// Last Modified On :
// Update Count     :
//

#include <bits/defs.hfa>
#include <fstream.hfa>
#include <kernel.hfa>
#include <thread.hfa>
#include <iofwd.hfa>

Duration default_preemption() {
	return 0;
}

enum { TIMES = 1000 };

volatile unsigned counter = 0;

// ----- Spinner -----
// spins trying to prevent other threads from getting to this processor
thread Spinner {};
void ^?{}(Spinner &mutex ) {}
void main(Spinner &) {
	unsigned last = 0;
	for() {
		unsigned curr = __atomic_load_n(&counter, __ATOMIC_SEQ_CST);

		if(curr >= TIMES) return;

		if(last == curr) {
			Pause();
			continue;
		}

		last = curr;
		yield();
	}
}

// ----- Submitter -----
// try to submit io but yield so that it's likely we are moved to the slow path
thread Submitter {};
void ^?{}(Submitter &mutex ) {}
void main(Submitter & this) {
	for(TIMES) {
		#if CFA_HAVE_LINUX_IO_URING_H
			io_future_t f;
			struct io_uring_sqe * sqe;
			__u32 idx;
			struct $io_context * ctx = cfa_io_allocate(&sqe, &idx, 1);

			zero_sqe(sqe);
			sqe->opcode = IORING_OP_NOP;
			sqe->user_data = (uintptr_t)&f;
		#endif

		yield( prng( this, 15 ) );

		#if CFA_HAVE_LINUX_IO_URING_H
			// Submit everything
			asm volatile("": : :"memory");
			cfa_io_submit( ctx, &idx, 1, false );
		#endif

		unsigned i = __atomic_add_fetch( &counter, 1, __ATOMIC_SEQ_CST );
		if(0 == (i % 100)) sout | i;

		#if CFA_HAVE_LINUX_IO_URING_H
			wait( f );
		#endif
	}
}

// ----- Yielder -----
// Add some chaos into the mix
thread Yielder {};
void ^?{}(Yielder &mutex ) {}
void main(Yielder&) {
	while(TIMES > __atomic_load_n(&counter, __ATOMIC_SEQ_CST)) {
		yield();
	}
}


int main() {
	processor p;
	sout | "starting";
	{
		Yielder y;
		Spinner s;
		Submitter io;
	}
	sout | "done";
}