//
// Cforall Version 1.0.0 Copyright (C) 2019 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// ready_queue.cfa --
//
// Author           : Thierry Delisle
// Created On       : Mon Nov dd 16:29:18 2019
// Last Modified By :
// Last Modified On :
// Update Count     :
//

#define __cforall_thread__
// #define __CFA_DEBUG_PRINT_READY_QUEUE__

#include "bits/defs.hfa"
#include "kernel_private.hfa"

#define _GNU_SOURCE
#include "stdlib.hfa"
#include "math.hfa"

static const size_t cache_line_size = 64;

// No overriden function, no environment variable, no define
// fall back to a magic number
#ifndef __CFA_MAX_PROCESSORS__
	#define __CFA_MAX_PROCESSORS__ 128
#endif

// returns the maximum number of processors the RWLock support
__attribute__((weak)) unsigned __max_processors() {
	const char * max_cores_s = getenv("CFA_MAX_PROCESSORS");
	if(!max_cores_s) {
		__cfadbg_print_nolock(ready_queue, "No CFA_MAX_PROCESSORS in ENV\n");
		return __CFA_MAX_PROCESSORS__;
	}

	char * endptr = 0p;
	long int max_cores_l = strtol(max_cores_s, &endptr, 10);
	if(max_cores_l < 1 || max_cores_l > 65535) {
		__cfadbg_print_nolock(ready_queue, "CFA_MAX_PROCESSORS out of range : %ld\n", max_cores_l);
		return __CFA_MAX_PROCESSORS__;
	}
	if('\0' != *endptr) {
		__cfadbg_print_nolock(ready_queue, "CFA_MAX_PROCESSORS not a decimal number : %s\n", max_cores_s);
		return __CFA_MAX_PROCESSORS__;
	}

	return max_cores_l;
}

//=======================================================================
// Cluster wide reader-writer lock
//=======================================================================
void  ?{}(__clusterRWLock_t & this) {
	this.max   = __max_processors();
	this.alloc = 0;
	this.ready = 0;
	this.lock  = false;
	this.data  = alloc(this.max);

	/*paranoid*/ verify( 0 == (((uintptr_t)(this.data    )) % 64) );
	/*paranoid*/ verify( 0 == (((uintptr_t)(this.data + 1)) % 64) );
	/*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.alloc), &this.alloc));
	/*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.ready), &this.ready));

}
void ^?{}(__clusterRWLock_t & this) {
	free(this.data);
}

void ?{}( __processor_id & this, struct processor * proc ) {
	this.handle = proc;
	this.lock   = false;
}

//=======================================================================
// Lock-Free registering/unregistering of threads
unsigned doregister2( struct cluster * cltr, struct processor * proc ) with(cltr->ready_lock) {
	__cfadbg_print_safe(ready_queue, "Kernel : Registering proc %p with cluster %p\n", proc, cltr);

	// Step - 1 : check if there is already space in the data
	uint_fast32_t s = ready;

	// Check among all the ready
	for(uint_fast32_t i = 0; i < s; i++) {
		processor * null = 0p; // Re-write every loop since compare thrashes it
		if( __atomic_load_n(&data[i].handle, (int)__ATOMIC_RELAXED) == null
			&& __atomic_compare_exchange_n( &data[i].handle, &null, proc, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
			/*paranoid*/ verify(i < ready);
			/*paranoid*/ verify(__alignof__(data[i]) == cache_line_size);
			/*paranoid*/ verify((((uintptr_t)&data[i]) % cache_line_size) == 0);
			return i;
		}
	}

	if(max <= alloc) abort("Trying to create more than %ud processors", cltr->ready_lock.max);

	// Step - 2 : F&A to get a new spot in the array.
	uint_fast32_t n = __atomic_fetch_add(&alloc, 1, __ATOMIC_SEQ_CST);
	if(max <= n) abort("Trying to create more than %ud processors", cltr->ready_lock.max);

	// Step - 3 : Mark space as used and then publish it.
	__processor_id * storage = (__processor_id *)&data[n];
	(*storage){ proc };
	while(true) {
		unsigned copy = n;
		if( __atomic_load_n(&ready, __ATOMIC_RELAXED) == n
			&& __atomic_compare_exchange_n(&ready, &copy, n + 1, true, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST))
			break;
		asm volatile("pause");
	}

	__cfadbg_print_safe(ready_queue, "Kernel : Registering proc %p done, id %lu\n", proc, n);

	// Return new spot.
	/*paranoid*/ verify(n < ready);
	/*paranoid*/ verify(__alignof__(data[n]) == cache_line_size);
	/*paranoid*/ verify((((uintptr_t)&data[n]) % cache_line_size) == 0);
	return n;
}

void unregister2( struct cluster * cltr, struct processor * proc ) with(cltr->ready_lock) {
	unsigned id = proc->id;
	/*paranoid*/ verify(id < ready);
	/*paranoid*/ verify(proc == __atomic_load_n(&data[id].handle, __ATOMIC_RELAXED));
	__atomic_store_n(&data[id].handle, 0p, __ATOMIC_RELEASE);

	__cfadbg_print_safe(ready_queue, "Kernel : Unregister proc %p\n", proc);
}

//-----------------------------------------------------------------------
// Writer side : acquire when changing the ready queue, e.g. adding more
//  queues or removing them.
uint_fast32_t ready_mutate_lock( struct cluster & cltr ) with(cltr.ready_lock) {
	// Step 1 : lock global lock
	// It is needed to avoid processors that register mid Critical-Section
	//   to simply lock their own lock and enter.
	__atomic_acquire( &lock );

	// Step 2 : lock per-proc lock
	// Processors that are currently being registered aren't counted
	//   but can't be in read_lock or in the critical section.
	// All other processors are counted
	uint_fast32_t s = ready;
	for(uint_fast32_t i = 0; i < s; i++) {
		__atomic_acquire( &data[i].lock );
	}

	return s;
}

void ready_mutate_unlock( struct cluster & cltr, uint_fast32_t last_s ) with(cltr.ready_lock) {
	// Step 1 : release local locks
	// This must be done while the global lock is held to avoid
	//   threads that where created mid critical section
	//   to race to lock their local locks and have the writer
	//   immidiately unlock them
	// Alternative solution : return s in write_lock and pass it to write_unlock
	for(uint_fast32_t i = 0; i < last_s; i++) {
		verify(data[i].lock);
		__atomic_store_n(&data[i].lock, (bool)false, __ATOMIC_RELEASE);
	}

	// Step 2 : release global lock
	/*paranoid*/ assert(true == lock);
	__atomic_store_n(&lock, (bool)false, __ATOMIC_RELEASE);
}

//=======================================================================
// Intrusive Queue used by ready queue
//=======================================================================
// Intrusives lanes which are used by the relaxed ready queue
struct __attribute__((aligned(128))) __intrusive_lane_t {
	// spin lock protecting the queue
	volatile bool lock;

	// anchor for the head and the tail of the queue
	struct __sentinel_t {
		// Link lists fields
		// instrusive link field for threads
		// must be exactly as in $thread
		__thread_desc_link link;
	} before, after;

#if defined(__CFA_WITH_VERIFY__)
	// id of last processor to acquire the lock
	// needed only to check for mutual exclusion violations
	unsigned int last_id;

	// number of items on this list
	// needed only to check for deadlocks
	unsigned int count;
#endif

	// Optional statistic counters
	#if !defined(__CFA_NO_SCHED_STATS__)
		struct __attribute__((aligned(64))) {
			// difference between number of push and pops
			ssize_t diff;

			// total number of pushes and pops
			size_t  push;
			size_t  pop ;
		} stat;
	#endif
};

void  ?{}(__intrusive_lane_t & this);
void ^?{}(__intrusive_lane_t & this);

// Get the head pointer (one before the first element) from the anchor
static inline $thread * head(const __intrusive_lane_t & this) {
	$thread * rhead = ($thread *)(
		(uintptr_t)( &this.before ) - offsetof( $thread, link )
	);
	/* paranoid */ verify(rhead);
	return rhead;
}

// Get the tail pointer (one after the last element) from the anchor
static inline $thread * tail(const __intrusive_lane_t & this) {
	$thread * rtail = ($thread *)(
		(uintptr_t)( &this.after ) - offsetof( $thread, link )
	);
	/* paranoid */ verify(rtail);
	return rtail;
}

// Ctor
void ?{}( __intrusive_lane_t & this ) {
	this.lock = false;
	#if defined(__CFA_WITH_VERIFY__)
		this.last_id = -1u;
		this.count = 0u;
	#endif

	this.before.link.prev = 0p;
	this.before.link.next = tail(this);
	this.before.link.ts   = 0;

	this.after .link.prev = head(this);
	this.after .link.next = 0p;
	this.after .link.ts   = 0;

	#if !defined(__CFA_NO_SCHED_STATS__)
		this.stat.diff = 0;
		this.stat.push = 0;
		this.stat.pop  = 0;
	#endif

	// We add a boat-load of assertions here because the anchor code is very fragile
	/* paranoid */ verify(((uintptr_t)( head(this) ) + offsetof( $thread, link )) == (uintptr_t)(&this.before));
	/* paranoid */ verify(((uintptr_t)( tail(this) ) + offsetof( $thread, link )) == (uintptr_t)(&this.after ));
	/* paranoid */ verify(head(this)->link.prev == 0p );
	/* paranoid */ verify(head(this)->link.next == tail(this) );
	/* paranoid */ verify(tail(this)->link.next == 0p );
	/* paranoid */ verify(tail(this)->link.prev == head(this) );
	/* paranoid */ verify(&head(this)->link.prev == &this.before.link.prev );
	/* paranoid */ verify(&head(this)->link.next == &this.before.link.next );
	/* paranoid */ verify(&tail(this)->link.prev == &this.after .link.prev );
	/* paranoid */ verify(&tail(this)->link.next == &this.after .link.next );
	/* paranoid */ verify(sizeof(__intrusive_lane_t) == 128);
	/* paranoid */ verify(sizeof(this) == 128);
	/* paranoid */ verify(__alignof__(__intrusive_lane_t) == 128);
	/* paranoid */ verify(__alignof__(this) == 128);
	/* paranoid */ verifyf(((intptr_t)(&this) % 128) == 0, "Expected address to be aligned %p %% 128 == %zd", &this, ((intptr_t)(&this) % 128));
}

// Dtor is trivial
void ^?{}( __intrusive_lane_t & this ) {
	// Make sure the list is empty
	/* paranoid */ verify(head(this)->link.prev == 0p );
	/* paranoid */ verify(head(this)->link.next == tail(this) );
	/* paranoid */ verify(tail(this)->link.next == 0p );
	/* paranoid */ verify(tail(this)->link.prev == head(this) );
	/* paranoid */ verify(this.count == 0u );
}

// Push a thread onto this lane
// returns true of lane was empty before push, false otherwise
bool push(__intrusive_lane_t & this, $thread * node) {
	#if defined(__CFA_WITH_VERIFY__)
		/* paranoid */ verify(this.lock);
		/* paranoid */ verify(node->link.ts != 0);
		/* paranoid */ verify(node->link.next == 0p);
		/* paranoid */ verify(node->link.prev == 0p);
		/* paranoid */ verify(tail(this)->link.next == 0p);
		/* paranoid */ verify(head(this)->link.prev == 0p);

		this.count++;

		if(this.before.link.ts == 0l) {
			/* paranoid */ verify(tail(this)->link.prev == head(this));
			/* paranoid */ verify(head(this)->link.next == tail(this));
		} else {
			/* paranoid */ verify(tail(this)->link.prev != head(this));
			/* paranoid */ verify(head(this)->link.next != tail(this));
		}
	#endif

	// Get the relevant nodes locally
	$thread * tail = tail(this);
	$thread * prev = tail->link.prev;

	// Do the push
	node->link.next = tail;
	node->link.prev = prev;
	prev->link.next = node;
	tail->link.prev = node;

	// Update stats
	#if !defined(__CFA_NO_SCHED_STATS__)
		this.stat.diff++;
		this.stat.push++;
	#endif

	verify(node->link.next == tail(this));

	// Check if the queue used to be empty
	if(this.before.link.ts == 0l) {
		this.before.link.ts = node->link.ts;
		/* paranoid */ verify(node->link.prev == head(this));
		return true;
	}
	return false;
}

// Pop a thread from this lane (must be non-empty)
// returns popped
// returns true of lane was empty before push, false otherwise
[$thread *, bool] pop(__intrusive_lane_t & this) {
	/* paranoid */ verify(this.lock);
	/* paranoid */ verify(this.before.link.ts != 0ul);

	// Get anchors locally
	$thread * head = head(this);
	$thread * tail = tail(this);

	// Get the relevant nodes locally
	$thread * node = head->link.next;
	$thread * next = node->link.next;

	#if defined(__CFA_WITH_VERIFY__)
		this.count--;
		/* paranoid */ verify(node != tail);
		/* paranoid */ verify(node);
	#endif

	// Do the pop
	head->link.next = next;
	next->link.prev = head;
	node->link.[next, prev] = 0p;

	// Update head time stamp
	this.before.link.ts = next->link.ts;

	// Update stats
	#ifndef __CFA_NO_SCHED_STATS__
		this.stat.diff--;
		this.stat.pop ++;
	#endif

	// Check if we emptied list and return accordingly
	/* paranoid */ verify(tail(this)->link.next == 0p);
	/* paranoid */ verify(head(this)->link.prev == 0p);
	if(next == tail) {
		/* paranoid */ verify(this.before.link.ts == 0);
		/* paranoid */ verify(tail(this)->link.prev == head(this));
		/* paranoid */ verify(head(this)->link.next == tail(this));
		return [node, true];
	}
	else {
		/* paranoid */ verify(next->link.ts != 0);
		/* paranoid */ verify(tail(this)->link.prev != head(this));
		/* paranoid */ verify(head(this)->link.next != tail(this));
		/* paranoid */ verify(this.before.link.ts != 0);
		return [node, false];
	}
}

// Check whether or not list is empty
static inline bool is_empty(__intrusive_lane_t & this) {
	// Cannot verify here since it may not be locked
	return this.before.link.ts == 0;
}

// Return the timestamp
static inline unsigned long long ts(__intrusive_lane_t & this) {
	// Cannot verify here since it may not be locked
	return this.before.link.ts;
}

//=======================================================================
// Scalable Non-Zero counter
//=======================================================================

union __snzi_val_t {
	uint64_t _all;
	struct __attribute__((packed)) {
		char cnt;
		uint64_t ver:56;
	};
};

bool cas(volatile __snzi_val_t & self, __snzi_val_t & exp, char _cnt, uint64_t _ver) {
	__snzi_val_t t;
	t.ver = _ver;
	t.cnt = _cnt;
	/* paranoid */ verify(t._all == ((_ver << 8) | ((unsigned char)_cnt)));
	return __atomic_compare_exchange_n(&self._all, &exp._all, t._all, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
}

bool cas(volatile __snzi_val_t & self, __snzi_val_t & exp, const __snzi_val_t & tar) {
	return __atomic_compare_exchange_n(&self._all, &exp._all, tar._all, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
}

void ?{}( __snzi_val_t & this ) { this._all = 0; }
void ?{}( __snzi_val_t & this, const volatile __snzi_val_t & o) { this._all = o._all; }

struct __attribute__((aligned(128))) __snzi_node_t {
	volatile __snzi_val_t value;
	struct __snzi_node_t * parent;
	bool is_root;
};

static inline void arrive( __snzi_node_t & );
static inline void depart( __snzi_node_t & );

#define __snzi_half -1

//--------------------------------------------------
// Root node
static void arrive_r( __snzi_node_t & this ) {
	/* paranoid */ verify( this.is_root );
	__atomic_fetch_add(&this.value._all, 1, __ATOMIC_SEQ_CST);
}

static void depart_r( __snzi_node_t & this ) {
	/* paranoid */ verify( this.is_root );
	__atomic_fetch_sub(&this.value._all, 1, __ATOMIC_SEQ_CST);
}

//--------------------------------------------------
// Hierarchical node
static void arrive_h( __snzi_node_t & this ) {
	int undoArr = 0;
	bool success = false;
	while(!success) {
		__snzi_val_t x = { this.value };
		/* paranoid */ verify(x.cnt <= 120);
		if( x.cnt >= 1 ) {
			if( cas( this.value, x, x.cnt + 1, x.ver ) ) {
				success = true;
			}
		}
		/* paranoid */ verify(x.cnt <= 120);
		if( x.cnt == 0 ) {
			if( cas( this.value, x, __snzi_half, x.ver + 1) ) {
				success = true;
				x.cnt = __snzi_half;
				x.ver = x.ver + 1;
			}
		}
		/* paranoid */ verify(x.cnt <= 120);
		if( x.cnt == __snzi_half ) {
			/* paranoid */ verify( this.parent);
			arrive( *this.parent );
			if( !cas( this.value, x, 1, x.ver) ) {
				undoArr = undoArr + 1;
			}
		}
	}

	for(int i = 0; i < undoArr; i++) {
		/* paranoid */ verify( this.parent );
		depart( *this.parent );
	}
}

static void depart_h( __snzi_node_t & this ) {
	while(true) {
		const __snzi_val_t x = { this.value };
		/* paranoid */ verifyf(x.cnt >= 1, "%d", x.cnt);
		if( cas( this.value, x, x.cnt - 1, x.ver ) ) {
			if( x.cnt == 1 ) {
				/* paranoid */ verify( this.parent );
				depart( *this.parent );
			}
			return;
		}
	}
}

//--------------------------------------------------
// All nodes
static inline void arrive( __snzi_node_t & this ) {
	if(this.is_root) arrive_r( this );
	else arrive_h( this );
}

static inline void depart( __snzi_node_t & this ) {
	if(this.is_root) depart_r( this );
	else depart_h( this );
}

static inline bool query( __snzi_node_t & this ) {
	/* paranoid */ verify( this.is_root );
	return this.value._all > 0;
}

//--------------------------------------------------
// SNZI object
void  ?{}( __snzi_t & this, unsigned depth ) with( this ) {
	mask = (1 << depth) - 1;
	root = (1 << (depth + 1)) - 2;
	nodes = alloc( root + 1 );

	int width = 1 << depth;
	for(int i = 0; i < root; i++) {
		nodes[i].value._all = 0;
		nodes[i].parent = &nodes[(i / 2) + width ];
		nodes[i].is_root = false;
	}

	nodes[ root ].value._all = 0;
	nodes[ root ].parent = 0p;
	nodes[ root ].is_root = true;
}

void ^?{}( __snzi_t & this ) {
	free( this.nodes );
}

static inline void arrive( __snzi_t & this, int idx) {
	idx &= this.mask;
	arrive( this.nodes[idx] );
}

static inline void depart( __snzi_t & this, int idx) {
	idx &= this.mask;
	depart( this.nodes[idx] );
}

static inline bool query( const __snzi_t & this ) {
	return query( this.nodes[ this.root ] );
}

//=======================================================================
// Cforall Reqdy Queue used by ready queue
//=======================================================================

// Thread local mirror of ready queue statistics
#if !defined(__CFA_NO_STATISTICS__)
static __attribute__((aligned(128))) thread_local struct {
	struct {
		struct {
			size_t attempt;
			size_t success;
		} push;
		struct {
			size_t maskrds;
			size_t attempt;
			size_t success;
		} pop;
	} pick;
	struct {
		size_t value;
		size_t count;
	} used;
} tls = {
	/* pick */{
		/* push */{ 0, 0 },
		/* pop  */{ 0, 0, 0 },
	},
	/* used */{ 0, 0 }
};
#endif

//-----------------------------------------------------------------------

void ?{}(__ready_queue_t & this) with (this) {

	lanes.data = alloc(4);
	for( i; 4 ) {
		(lanes.data[i]){};
	}
	lanes.count = 4;
	snzi{ log2( lanes.count / 8 ) };

	#if !defined(__CFA_NO_STATISTICS__)
		global_stats.pick.push.attempt = 0;
		global_stats.pick.push.success = 0;
		global_stats.pick.pop .maskrds = 0;
		global_stats.pick.pop .attempt = 0;
		global_stats.pick.pop .success = 0;

		global_stats.used.value = 0;
		global_stats.used.count = 0;
	#endif
}

void ^?{}(__ready_queue_t & this) with (this) {
	verify( 4  == lanes.count );
	verify( !query( snzi ) );

	^(snzi){};

	for( i; 4 ) {
		^(lanes.data[i]){};
	}
	free(lanes.data);
}

//-----------------------------------------------------------------------
__attribute__((hot)) bool push(struct cluster * cltr, struct $thread * thrd) with (cltr->ready_queue) {
	__cfadbg_print_safe(ready_queue, "Kernel : Pushing %p on cluster %p\n", thrd, cltr);

	// write timestamp
	thrd->link.ts = rdtscl();

	// Try to pick a lane and lock it
	unsigned i;
	do {
		// Pick the index of a lane
		i = __tls_rand() % lanes.count;

		#if !defined(__CFA_NO_STATISTICS__)
			tls.pick.push.attempt++;
		#endif

		// If we can't lock it retry
	} while( !__atomic_try_acquire( &lanes.data[i].lock ) );

	#if defined(__CFA_WITH_VERIFY__)
		/* paranoid */ verify(lanes.data[i].last_id == -1u);
		/* paranoid */ lanes.data[i].last_id = kernelTLS.this_processor->id;
	#endif

	bool first = false;

	// Actually push it
	bool lane_first = push(lanes.data[i], thrd);

	// If this lane used to be empty we need to do more
	if(lane_first) {
		// Check if the entire queue used to be empty
		first = !query(snzi);

		// Update the snzi
		arrive( snzi, i );
	}

	#if defined(__CFA_WITH_VERIFY__)
		/* paranoid */ verifyf( lanes.data[i].last_id == kernelTLS.this_processor->id, "Expected last processor to lock queue %u to be %u, was %u\n", i, lanes.data[i].last_id, kernelTLS.this_processor->id );
		/* paranoid */ verifyf( lanes.data[i].lock, "List %u is not locked\n", i );
		/* paranoid */ lanes.data[i].last_id = -1u;
	#endif

	// Unlock and return
	__atomic_unlock( &lanes.data[i].lock );

	__cfadbg_print_safe(ready_queue, "Kernel : Pushed %p on cluster %p (idx: %u, mask %llu, first %d)\n", thrd, cltr, i, used.mask[0], lane_first);

	// Update statistics
	#if !defined(__CFA_NO_STATISTICS__)
		tls.pick.push.success++;
	#endif

	// return whether or not the list was empty before this push
	return first;
}

//-----------------------------------------------------------------------
// Given 2 indexes, pick the list with the oldest push an try to pop from it
static struct $thread * try_pop(struct cluster * cltr, unsigned i, unsigned j) with (cltr->ready_queue) {
	#if !defined(__CFA_NO_STATISTICS__)
		tls.pick.pop.attempt++;
	#endif

	// Pick the bet list
	int w = i;
	if( __builtin_expect(!is_empty(lanes.data[j]), true) ) {
		w = (ts(lanes.data[i]) < ts(lanes.data[j])) ? i : j;
	}

	// Get relevant elements locally
	__intrusive_lane_t & lane = lanes.data[w];

	// If list looks empty retry
	if( is_empty(lane) ) return 0p;

	// If we can't get the lock retry
	if( !__atomic_try_acquire(&lane.lock) ) return 0p;

	#if defined(__CFA_WITH_VERIFY__)
		/* paranoid */ verify(lane.last_id == -1u);
		/* paranoid */ lane.last_id = kernelTLS.this_processor->id;
	#endif


	// If list is empty, unlock and retry
	if( is_empty(lane) ) {
		#if defined(__CFA_WITH_VERIFY__)
			/* paranoid */ verify(lane.last_id == kernelTLS.this_processor->id);
			/* paranoid */ lane.last_id = -1u;
		#endif

		__atomic_unlock(&lane.lock);
		return 0p;
	}

	// Actually pop the list
	struct $thread * thrd;
	bool emptied;
	[thrd, emptied] = pop(lane);

	/* paranoid */ verify(thrd);
	/* paranoid */ verify(lane.last_id == kernelTLS.this_processor->id);
	/* paranoid */ verify(lane.lock);

	// If this was the last element in the lane
	if(emptied) {
		depart( snzi, w );
	}

	#if defined(__CFA_WITH_VERIFY__)
		/* paranoid */ verify(lane.last_id == kernelTLS.this_processor->id);
		/* paranoid */ lane.last_id = -1u;
	#endif

	// Unlock and return
	__atomic_unlock(&lane.lock);

	// Update statistics
	#if !defined(__CFA_NO_STATISTICS__)
		tls.pick.pop.success++;
	#endif

	// return the popped thread
	return thrd;
}

// Pop from the ready queue from a given cluster
__attribute__((hot)) $thread * pop(struct cluster * cltr) with (cltr->ready_queue) {
	/* paranoid */ verify( lanes.count > 0 );

	// As long as the list is not empty, try finding a lane that isn't empty and pop from it
	while( query(snzi) ) {
		// Pick two lists at random
		int i = __tls_rand() % __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
		int j = __tls_rand() % __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );

		// try popping from the 2 picked lists
		struct $thread * thrd = try_pop(cltr, i, j);
		if(thrd) return thrd;
	}

	// All lanes where empty return 0p
	return 0p;
}

//-----------------------------------------------------------------------

static void check( __ready_queue_t & q ) with (q) {
	#if defined(__CFA_WITH_VERIFY__)
		{
			for( idx ; lanes.count ) {
				__intrusive_lane_t & sl = lanes.data[idx];
				assert(!lanes.data[idx].lock);

				assert(head(sl)->link.prev == 0p );
				assert(head(sl)->link.next->link.prev == head(sl) );
				assert(tail(sl)->link.next == 0p );
				assert(tail(sl)->link.prev->link.next == tail(sl) );

				if(sl.before.link.ts == 0l) {
					assert(tail(sl)->link.prev == head(sl));
					assert(head(sl)->link.next == tail(sl));
				} else {
					assert(tail(sl)->link.prev != head(sl));
					assert(head(sl)->link.next != tail(sl));
				}
			}
		}
	#endif
}

// Call this function of the intrusive list was moved using memcpy
// fixes the list so that the pointers back to anchors aren't left dangling
static inline void fix(__intrusive_lane_t & ll) {
	// if the list is not empty then follow he pointer and fix its reverse
	if(!is_empty(ll)) {
		head(ll)->link.next->link.prev = head(ll);
		tail(ll)->link.prev->link.next = tail(ll);
	}
	// Otherwise just reset the list
	else {
		verify(tail(ll)->link.next == 0p);
		tail(ll)->link.prev = head(ll);
		head(ll)->link.next = tail(ll);
		verify(head(ll)->link.prev == 0p);
	}
}

// Grow the ready queue
void ready_queue_grow  (struct cluster * cltr) {
	// Lock the RWlock so no-one pushes/pops while we are changing the queue
	uint_fast32_t last_size = ready_mutate_lock( *cltr );

	__cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue\n");

	// Make sure that everything is consistent
	/* paranoid */ check( cltr->ready_queue );

	// grow the ready queue
	with( cltr->ready_queue ) {
		^(snzi){};

		size_t ncount = lanes.count;

		// increase count
		ncount += 4;

		// Allocate new array (uses realloc and memcpies the data)
		lanes.data = alloc(lanes.data, ncount);

		// Fix the moved data
		for( idx; (size_t)lanes.count ) {
			fix(lanes.data[idx]);
		}

		// Construct new data
		for( idx; (size_t)lanes.count ~ ncount) {
			(lanes.data[idx]){};
		}

		// Update original
		lanes.count = ncount;

		// Re-create the snzi
		snzi{ log2( lanes.count / 8 ) };
		for( idx; (size_t)lanes.count ) {
			if( !is_empty(lanes.data[idx]) ) {
				arrive(snzi, idx);
			}
		}
	}

	// Make sure that everything is consistent
	/* paranoid */ check( cltr->ready_queue );

	__cfadbg_print_safe(ready_queue, "Kernel : Growing ready queue done\n");

	// Unlock the RWlock
	ready_mutate_unlock( *cltr, last_size );
}

// Shrink the ready queue
void ready_queue_shrink(struct cluster * cltr) {
	// Lock the RWlock so no-one pushes/pops while we are changing the queue
	uint_fast32_t last_size = ready_mutate_lock( *cltr );

	__cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue\n");

	// Make sure that everything is consistent
	/* paranoid */ check( cltr->ready_queue );

	with( cltr->ready_queue ) {
		^(snzi){};

		// Make sure that the total thread count stays the same
		#if defined(__CFA_WITH_VERIFY__)
			size_t nthreads = 0;
			for( idx; (size_t)lanes.count ) {
				nthreads += lanes.data[idx].count;
			}
		#endif

		size_t ocount = lanes.count;
		// Check that we have some space left
		if(ocount < 8) abort("Program attempted to destroy more Ready Queues than were created");

		// reduce the actual count so push doesn't use the old queues
		lanes.count -= 4;
		verify(ocount > lanes.count);

		// for printing count the number of displaced threads
		#if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
			__attribute__((unused)) size_t displaced = 0;
		#endif

		// redistribute old data
		for( idx; (size_t)lanes.count ~ ocount) {
			// Lock is not strictly needed but makes checking invariants much easier
			__attribute__((unused)) bool locked = __atomic_try_acquire(&lanes.data[idx].lock);
			verify(locked);

			// As long as we can pop from this lane to push the threads somewhere else in the queue
			while(!is_empty(lanes.data[idx])) {
				struct $thread * thrd;
				__attribute__((unused)) bool _;
				[thrd, _] = pop(lanes.data[idx]);

				push(cltr, thrd);

				// for printing count the number of displaced threads
				#if defined(__CFA_DEBUG_PRINT__) || defined(__CFA_DEBUG_PRINT_READY_QUEUE__)
					displaced++;
				#endif
			}

			// Unlock the lane
			__atomic_unlock(&lanes.data[idx].lock);

			// TODO print the queue statistics here

			^(lanes.data[idx]){};
		}

		__cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue displaced %zu threads\n", displaced);

		// Allocate new array (uses realloc and memcpies the data)
		lanes.data = alloc(lanes.data, lanes.count);

		// Fix the moved data
		for( idx; (size_t)lanes.count ) {
			fix(lanes.data[idx]);
		}

		// Re-create the snzi
		snzi{ log2( lanes.count / 8 ) };
		for( idx; (size_t)lanes.count ) {
			if( !is_empty(lanes.data[idx]) ) {
				arrive(snzi, idx);
			}
		}

		// Make sure that the total thread count stayed the same
		#if defined(__CFA_WITH_VERIFY__)
			for( idx; (size_t)lanes.count ) {
				nthreads -= lanes.data[idx].count;
			}
			verifyf(nthreads == 0, "Shrinking changed number of threads");
		#endif
	}

	// Make sure that everything is consistent
	/* paranoid */ check( cltr->ready_queue );

	__cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue done\n");

	// Unlock the RWlock
	ready_mutate_unlock( *cltr, last_size );
}

//-----------------------------------------------------------------------

#if !defined(__CFA_NO_STATISTICS__)
void stats_tls_tally(struct cluster * cltr) with (cltr->ready_queue) {
	__atomic_fetch_add( &global_stats.pick.push.attempt, tls.pick.push.attempt, __ATOMIC_SEQ_CST );
	__atomic_fetch_add( &global_stats.pick.push.success, tls.pick.push.success, __ATOMIC_SEQ_CST );
	__atomic_fetch_add( &global_stats.pick.pop .maskrds, tls.pick.pop .maskrds, __ATOMIC_SEQ_CST );
	__atomic_fetch_add( &global_stats.pick.pop .attempt, tls.pick.pop .attempt, __ATOMIC_SEQ_CST );
	__atomic_fetch_add( &global_stats.pick.pop .success, tls.pick.pop .success, __ATOMIC_SEQ_CST );

	__atomic_fetch_add( &global_stats.used.value, tls.used.value, __ATOMIC_SEQ_CST );
	__atomic_fetch_add( &global_stats.used.count, tls.used.count, __ATOMIC_SEQ_CST );
}
#endif