source: libcfa/src/concurrency/ready_queue.cfa @ 3c4bf05

//
// 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 _GNU_SOURCE

// #define __CFA_DEBUG_PRINT_READY_QUEUE__


#define USE_AWARE_STEALING

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

#include "stdlib.hfa"
#include "limits.hfa"
#include "math.hfa"

#include <errno.h>
#include <unistd.h>

extern "C" {
        #include <sys/syscall.h>  // __NR_xxx
}

#include "ready_subqueue.hfa"

static const size_t cache_line_size = 64;

#if !defined(__CFA_NO_STATISTICS__)
        #define __STATS(...) __VA_ARGS__
#else
        #define __STATS(...)
#endif

// No overriden function, no environment variable, no define
// fall back to a magic number
#ifndef __CFA_MAX_PROCESSORS__
        #define __CFA_MAX_PROCESSORS__ 1024
#endif

#define READYQ_SHARD_FACTOR 2
#define SEQUENTIAL_SHARD 2

static inline struct thread$ * try_pop(struct cluster * cltr, unsigned w __STATS(, __stats_readyQ_pop_t & stats));
static inline struct thread$ * try_pop(struct cluster * cltr, unsigned i, unsigned j __STATS(, __stats_readyQ_pop_t & stats));
static inline struct thread$ * search(struct cluster * cltr);


// 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;
}

#if   defined(CFA_HAVE_LINUX_LIBRSEQ)
        // No forward declaration needed
        #define __kernel_rseq_register rseq_register_current_thread
        #define __kernel_rseq_unregister rseq_unregister_current_thread
#elif defined(CFA_HAVE_LINUX_RSEQ_H)
        static void __kernel_raw_rseq_register  (void);
        static void __kernel_raw_rseq_unregister(void);

        #define __kernel_rseq_register __kernel_raw_rseq_register
        #define __kernel_rseq_unregister __kernel_raw_rseq_unregister
#else
        // No forward declaration needed
        // No initialization needed
        static inline void noop(void) {}

        #define __kernel_rseq_register noop
        #define __kernel_rseq_unregister noop
#endif

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

        /*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.alloc), &this.alloc));
        /*paranoid*/ verify(__atomic_is_lock_free(sizeof(this.ready), &this.ready));

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


//=======================================================================
// Lock-Free registering/unregistering of threads
unsigned register_proc_id( void ) with(*__scheduler_lock) {
        __kernel_rseq_register();

        bool * handle = (bool *)&kernelTLS().sched_lock;

        // 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++) {
                bool * volatile * cell = (bool * volatile *)&data[i]; // Cforall is bugged and the double volatiles causes problems
                /* paranoid */ verify( handle != *cell );

                bool * null = 0p; // Re-write every loop since compare thrashes it
                if( __atomic_load_n(cell, (int)__ATOMIC_RELAXED) == null
                        && __atomic_compare_exchange_n( cell, &null, handle, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
                        /* paranoid */ verify(i < ready);
                        /* paranoid */ verify( (kernelTLS().sched_id = i, true) );
                        return i;
                }
        }

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

        // Step - 3 : Mark space as used and then publish it.
        data[n] = handle;
        while() {
                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;
                Pause();
        }

        // Return new spot.
        /* paranoid */ verify(n < ready);
        /* paranoid */ verify( (kernelTLS().sched_id = n, true) );
        return n;
}

void unregister_proc_id( unsigned id ) with(*__scheduler_lock) {
        /* paranoid */ verify(id < ready);
        /* paranoid */ verify(id == kernelTLS().sched_id);
        /* paranoid */ verify(data[id] == &kernelTLS().sched_lock);

        bool * volatile * cell = (bool * volatile *)&data[id]; // Cforall is bugged and the double volatiles causes problems

        __atomic_store_n(cell, 0p, __ATOMIC_RELEASE);

        __kernel_rseq_unregister();
}

//-----------------------------------------------------------------------
// Writer side : acquire when changing the ready queue, e.g. adding more
//  queues or removing them.
uint_fast32_t ready_mutate_lock( void ) with(*__scheduler_lock) {
        /* paranoid */ verify( ! __preemption_enabled() );

        // 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( &write_lock );

        // Make sure we won't deadlock ourself
        // Checking before acquiring the writer lock isn't safe
        // because someone else could have locked us.
        /* paranoid */ verify( ! kernelTLS().sched_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++) {
                volatile bool * llock = data[i];
                if(llock) __atomic_acquire( llock );
        }

        /* paranoid */ verify( ! __preemption_enabled() );
        return s;
}

void ready_mutate_unlock( uint_fast32_t last_s ) with(*__scheduler_lock) {
        /* paranoid */ verify( ! __preemption_enabled() );

        // 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++) {
                volatile bool * llock = data[i];
                if(llock) __atomic_store_n(llock, (bool)false, __ATOMIC_RELEASE);
        }

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

        /* paranoid */ verify( ! __preemption_enabled() );
}

//=======================================================================
// Cforall Ready Queue used for scheduling
//=======================================================================
unsigned long long moving_average(unsigned long long currtsc, unsigned long long instsc, unsigned long long old_avg) {
        /* paranoid */ verifyf( currtsc < 45000000000000000, "Suspiciously large current time: %'llu (%llx)\n", currtsc, currtsc );
        /* paranoid */ verifyf( instsc  < 45000000000000000, "Suspiciously large insert time: %'llu (%llx)\n", instsc, instsc );
        /* paranoid */ verifyf( old_avg < 15000000000000, "Suspiciously large previous average: %'llu (%llx)\n", old_avg, old_avg );

        const unsigned long long new_val = currtsc > instsc ? currtsc - instsc : 0;
        const unsigned long long total_weight = 16;
        const unsigned long long new_weight   = 4;
        const unsigned long long old_weight = total_weight - new_weight;
        const unsigned long long ret = ((new_weight * new_val) + (old_weight * old_avg)) / total_weight;
        return ret;
}

void ?{}(__ready_queue_t & this) with (this) {
        lanes.data   = 0p;
        lanes.tscs   = 0p;
        lanes.caches = 0p;
        lanes.help   = 0p;
        lanes.count  = 0;
}

void ^?{}(__ready_queue_t & this) with (this) {
        free(lanes.data);
        free(lanes.tscs);
        free(lanes.caches);
        free(lanes.help);
}

//-----------------------------------------------------------------------
__attribute__((hot)) void push(struct cluster * cltr, struct thread$ * thrd, unpark_hint hint) with (cltr->ready_queue) {
        processor * const proc = kernelTLS().this_processor;
        const bool external = (!proc) || (cltr != proc->cltr);
        const bool remote   = hint == UNPARK_REMOTE;

        unsigned i;
        if( external || remote ) {
                // Figure out where thread was last time and make sure it's valid
                /* paranoid */ verify(thrd->preferred >= 0);
                if(thrd->preferred * READYQ_SHARD_FACTOR < lanes.count) {
                        /* paranoid */ verify(thrd->preferred * READYQ_SHARD_FACTOR < lanes.count);
                        unsigned start = thrd->preferred * READYQ_SHARD_FACTOR;
                        do {
                                unsigned r = __tls_rand();
                                i = start + (r % READYQ_SHARD_FACTOR);
                                /* paranoid */ verify( i < lanes.count );
                                // If we can't lock it retry
                        } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
                } else {
                        do {
                                i = __tls_rand() % lanes.count;
                        } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
                }
        } else {
                do {
                        unsigned r = proc->rdq.its++;
                        i = proc->rdq.id + (r % READYQ_SHARD_FACTOR);
                        /* paranoid */ verify( i < lanes.count );
                        // If we can't lock it retry
                } while( !__atomic_try_acquire( &lanes.data[i].lock ) );
        }

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

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

        #if !defined(__CFA_NO_STATISTICS__)
                if(unlikely(external || remote)) __atomic_fetch_add(&cltr->stats->ready.push.extrn.success, 1, __ATOMIC_RELAXED);
                else __tls_stats()->ready.push.local.success++;
        #endif
}

static inline unsigned long long calc_cutoff(const unsigned long long ctsc, const processor * proc, __ready_queue_t & rdq) {
        unsigned start = proc->rdq.id;
        unsigned long long max = 0;
        for(i; READYQ_SHARD_FACTOR) {
                unsigned long long ptsc = ts(rdq.lanes.data[start + i]);
                if(ptsc != -1ull) {
                        /* paranoid */ verify( start + i < rdq.lanes.count );
                        unsigned long long tsc = moving_average(ctsc, ptsc, rdq.lanes.tscs[start + i].ma);
                        if(tsc > max) max = tsc;
                }
        }
        return (max + 2 * max) / 2;
}

__attribute__((hot)) struct thread$ * pop_fast(struct cluster * cltr) with (cltr->ready_queue) {
        /* paranoid */ verify( lanes.count > 0 );
        /* paranoid */ verify( kernelTLS().this_processor );
        /* paranoid */ verify( kernelTLS().this_processor->rdq.id < lanes.count );

        processor * const proc = kernelTLS().this_processor;
        unsigned this = proc->rdq.id;
        /* paranoid */ verify( this < lanes.count );
        __cfadbg_print_safe(ready_queue, "Kernel : pop from %u\n", this);

        // Figure out the current cpu and make sure it is valid
        const int cpu = __kernel_getcpu();
        /* paranoid */ verify(cpu >= 0);
        /* paranoid */ verify(cpu < cpu_info.hthrd_count);
        unsigned this_cache = cpu_info.llc_map[cpu].cache;

        // Super important: don't write the same value over and over again
        // We want to maximise our chances that his particular values stays in cache
        if(lanes.caches[this / READYQ_SHARD_FACTOR].id != this_cache)
                __atomic_store_n(&lanes.caches[this / READYQ_SHARD_FACTOR].id, this_cache, __ATOMIC_RELAXED);

        const unsigned long long ctsc = rdtscl();

        if(proc->rdq.target == MAX) {
                uint64_t chaos = __tls_rand();
                unsigned ext = chaos & 0xff;
                unsigned other  = (chaos >> 8) % (lanes.count);

                if(ext < 3 || __atomic_load_n(&lanes.caches[other / READYQ_SHARD_FACTOR].id, __ATOMIC_RELAXED) == this_cache) {
                        proc->rdq.target = other;
                }
        }
        else {
                const unsigned target = proc->rdq.target;
                __cfadbg_print_safe(ready_queue, "Kernel : %u considering helping %u, tcsc %llu\n", this, target, lanes.tscs[target].tv);
                /* paranoid */ verify( lanes.tscs[target].tv != MAX );
                if(target < lanes.count) {
                        const unsigned long long cutoff = calc_cutoff(ctsc, proc, cltr->ready_queue);
                        const unsigned long long age = moving_average(ctsc, lanes.tscs[target].tv, lanes.tscs[target].ma);
                        __cfadbg_print_safe(ready_queue, "Kernel : Help attempt on %u from %u, age %'llu vs cutoff %'llu, %s\n", target, this, age, cutoff, age > cutoff ? "yes" : "no");
                        if(age > cutoff) {
                                thread$ * t = try_pop(cltr, target __STATS(, __tls_stats()->ready.pop.help));
                                if(t) return t;
                        }
                }
                proc->rdq.target = MAX;
        }

        for(READYQ_SHARD_FACTOR) {
                unsigned i = this + (proc->rdq.itr++ % READYQ_SHARD_FACTOR);
                if(thread$ * t = try_pop(cltr, i __STATS(, __tls_stats()->ready.pop.local))) return t;
        }

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

}
__attribute__((hot)) struct thread$ * pop_slow(struct cluster * cltr) with (cltr->ready_queue) {
        unsigned i = __tls_rand() % lanes.count;
        return try_pop(cltr, i __STATS(, __tls_stats()->ready.pop.steal));
}
__attribute__((hot)) struct thread$ * pop_search(struct cluster * cltr) {
        return search(cltr);
}

//=======================================================================
// Various Ready Queue utilities
//=======================================================================
// these function work the same or almost the same
// whether they are using work-stealing or relaxed fifo scheduling

//-----------------------------------------------------------------------
// try to pop from a lane given by index w
static inline struct thread$ * try_pop(struct cluster * cltr, unsigned w __STATS(, __stats_readyQ_pop_t & stats)) with (cltr->ready_queue) {
        /* paranoid */ verify( w < lanes.count );
        __STATS( stats.attempt++; )

        // 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 list is empty, unlock and retry
        if( is_empty(lane) ) {
                __atomic_unlock(&lane.lock);
                return 0p;
        }

        // Actually pop the list
        struct thread$ * thrd;
        unsigned long long tsc_before = ts(lane);
        unsigned long long tsv;
        [thrd, tsv] = pop(lane);

        /* paranoid */ verify(thrd);
        /* paranoid */ verify(tsv);
        /* paranoid */ verify(lane.lock);

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

        // Update statistics
        __STATS( stats.success++; )

        if (tsv != MAX) {
                unsigned long long now = rdtscl();
                unsigned long long pma = __atomic_load_n(&lanes.tscs[w].ma, __ATOMIC_RELAXED);
                __atomic_store_n(&lanes.tscs[w].tv, tsv, __ATOMIC_RELAXED);
                __atomic_store_n(&lanes.tscs[w].ma, moving_average(now, tsc_before, pma), __ATOMIC_RELAXED);
        }

        thrd->preferred = w / READYQ_SHARD_FACTOR;

        // return the popped thread
        return thrd;
}

//-----------------------------------------------------------------------
// try to pop from any lanes making sure you don't miss any threads push
// before the start of the function
static inline struct thread$ * search(struct cluster * cltr) with (cltr->ready_queue) {
        /* paranoid */ verify( lanes.count > 0 );
        unsigned count = __atomic_load_n( &lanes.count, __ATOMIC_RELAXED );
        unsigned offset = __tls_rand();
        for(i; count) {
                unsigned idx = (offset + i) % count;
                struct thread$ * thrd = try_pop(cltr, idx __STATS(, __tls_stats()->ready.pop.search));
                if(thrd) {
                        return thrd;
                }
        }

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

//-----------------------------------------------------------------------
// get preferred ready for new thread
unsigned ready_queue_new_preferred() {
        unsigned pref = MAX;
        if(struct thread$ * thrd = publicTLS_get( this_thread )) {
                pref = thrd->preferred;
        }

        return pref;
}

//-----------------------------------------------------------------------
// Check that all the intrusive queues in the data structure are still consistent
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);

                                        if(is_empty(sl)) {
                                                assert( sl.anchor.next == 0p );
                                                assert( sl.anchor.ts   == -1llu );
                                                assert( mock_head(sl)  == sl.prev );
                                        } else {
                                                assert( sl.anchor.next != 0p );
                                                assert( sl.anchor.ts   != -1llu );
                                                assert( mock_head(sl)  != sl.prev );
                                        }
                        }
                }
        #endif
}

//-----------------------------------------------------------------------
// Given 2 indexes, pick the list with the oldest push an try to pop from it
static inline struct thread$ * try_pop(struct cluster * cltr, unsigned i, unsigned j __STATS(, __stats_readyQ_pop_t & stats)) with (cltr->ready_queue) {
        // 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;
        }

        return try_pop(cltr, w __STATS(, stats));
}

// 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(is_empty(ll)) {
                                verify(ll.anchor.next == 0p);
                                ll.prev = mock_head(ll);
                        }
}

static void assign_list(unsigned & value, dlist(processor) & list, unsigned count) {
        processor * it = &list`first;
        for(unsigned i = 0; i < count; i++) {
                /* paranoid */ verifyf( it, "Unexpected null iterator, at index %u of %u\n", i, count);
                it->rdq.id = value;
                it->rdq.target = MAX;
                value += READYQ_SHARD_FACTOR;
                it = &(*it)`next;
        }
}

static void reassign_cltr_id(struct cluster * cltr) {
        unsigned preferred = 0;
        assign_list(preferred, cltr->procs.actives, cltr->procs.total - cltr->procs.idle);
        assign_list(preferred, cltr->procs.idles  , cltr->procs.idle );
}

static void fix_times( struct cluster * cltr ) with( cltr->ready_queue ) {
        lanes.tscs = alloc(lanes.count, lanes.tscs`realloc);
        for(i; lanes.count) {
                lanes.tscs[i].tv = rdtscl();
                lanes.tscs[i].ma = 0;
        }
}

// Grow the ready queue
void ready_queue_grow(struct cluster * cltr) {
        size_t ncount;
        int target = cltr->procs.total;

        /* paranoid */ verify( ready_mutate_islocked() );
        __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 ) {
                // Find new count
                // Make sure we always have atleast 1 list
                if(target >= 2) {
                        ncount = target * READYQ_SHARD_FACTOR;
                } else {
                        ncount = SEQUENTIAL_SHARD;
                }

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

                // 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;

                lanes.caches = alloc( target, lanes.caches`realloc );
        }

        fix_times(cltr);

        reassign_cltr_id(cltr);

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

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

        /* paranoid */ verify( ready_mutate_islocked() );
}

// Shrink the ready queue
void ready_queue_shrink(struct cluster * cltr) {
        /* paranoid */ verify( ready_mutate_islocked() );
        __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue\n");

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

        int target = cltr->procs.total;

        with( cltr->ready_queue ) {
                // Remember old count
                size_t ocount = lanes.count;

                // Find new count
                // Make sure we always have atleast 1 list
                lanes.count = target >= 2 ? target * READYQ_SHARD_FACTOR: SEQUENTIAL_SHARD;
                /* paranoid */ verify( ocount >= lanes.count );
                /* paranoid */ verify( lanes.count == target * READYQ_SHARD_FACTOR || target < 2 );

                // 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;
                                unsigned long long _;
                                [thrd, _] = pop(lanes.data[idx]);

                                push(cltr, thrd, true);

                                // 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.count, lanes.data`realloc );

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

                lanes.caches = alloc( target, lanes.caches`realloc );
        }

        fix_times(cltr);


        reassign_cltr_id(cltr);

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

        __cfadbg_print_safe(ready_queue, "Kernel : Shrinking ready queue done\n");
        /* paranoid */ verify( ready_mutate_islocked() );
}

#if !defined(__CFA_NO_STATISTICS__)
        unsigned cnt(const __ready_queue_t & this, unsigned idx) {
                /* paranoid */ verify(this.lanes.count > idx);
                return this.lanes.data[idx].cnt;
        }
#endif


#if   defined(CFA_HAVE_LINUX_LIBRSEQ)
        // No definition needed
#elif defined(CFA_HAVE_LINUX_RSEQ_H)

        #if defined( __x86_64 ) || defined( __i386 )
                #define RSEQ_SIG        0x53053053
        #elif defined( __ARM_ARCH )
                #ifdef __ARMEB__
                #define RSEQ_SIG    0xf3def5e7      /* udf    #24035    ; 0x5de3 (ARMv6+) */
                #else
                #define RSEQ_SIG    0xe7f5def3      /* udf    #24035    ; 0x5de3 */
                #endif
        #endif

        extern void __disable_interrupts_hard();
        extern void __enable_interrupts_hard();

        static void __kernel_raw_rseq_register  (void) {
                /* paranoid */ verify( __cfaabi_rseq.cpu_id == RSEQ_CPU_ID_UNINITIALIZED );

                // int ret = syscall(__NR_rseq, &__cfaabi_rseq, sizeof(struct rseq), 0, (sigset_t *)0p, _NSIG / 8);
                int ret = syscall(__NR_rseq, &__cfaabi_rseq, sizeof(struct rseq), 0, RSEQ_SIG);
                if(ret != 0) {
                        int e = errno;
                        switch(e) {
                        case EINVAL: abort("KERNEL ERROR: rseq register invalid argument");
                        case ENOSYS: abort("KERNEL ERROR: rseq register no supported");
                        case EFAULT: abort("KERNEL ERROR: rseq register with invalid argument");
                        case EBUSY : abort("KERNEL ERROR: rseq register already registered");
                        case EPERM : abort("KERNEL ERROR: rseq register sig  argument  on unregistration does not match the signature received on registration");
                        default: abort("KERNEL ERROR: rseq register unexpected return %d", e);
                        }
                }
        }

        static void __kernel_raw_rseq_unregister(void) {
                /* paranoid */ verify( __cfaabi_rseq.cpu_id >= 0 );

                // int ret = syscall(__NR_rseq, &__cfaabi_rseq, sizeof(struct rseq), RSEQ_FLAG_UNREGISTER, (sigset_t *)0p, _NSIG / 8);
                int ret = syscall(__NR_rseq, &__cfaabi_rseq, sizeof(struct rseq), RSEQ_FLAG_UNREGISTER, RSEQ_SIG);
                if(ret != 0) {
                        int e = errno;
                        switch(e) {
                        case EINVAL: abort("KERNEL ERROR: rseq unregister invalid argument");
                        case ENOSYS: abort("KERNEL ERROR: rseq unregister no supported");
                        case EFAULT: abort("KERNEL ERROR: rseq unregister with invalid argument");
                        case EBUSY : abort("KERNEL ERROR: rseq unregister already registered");
                        case EPERM : abort("KERNEL ERROR: rseq unregister sig  argument  on unregistration does not match the signature received on registration");
                        default: abort("KERNEL ERROR: rseq unregisteunexpected return %d", e);
                        }
                }
        }
#else
        // No definition needed
#endif