source: libcfa/src/concurrency/kernel_private.hfa@ d2278e9

//
// Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// kernel_private.hfa --
//
// Author           : Thierry Delisle
// Created On       : Mon Feb 13 12:27:26 2017
// Last Modified By : Peter A. Buhr
// Last Modified On : Wed Aug 12 08:21:33 2020
// Update Count     : 9
//

#pragma once

#if !defined(__cforall_thread__)
        #error kernel_private.hfa should only be included in libcfathread source
#endif

#include "kernel.hfa"
#include "thread.hfa"

#include "alarm.hfa"
#include "stats.hfa"

extern "C" {
#if   defined(CFA_HAVE_LINUX_LIBRSEQ)
        #include <rseq/rseq.h>
#elif defined(CFA_HAVE_LINUX_RSEQ_H)
        #include <linux/rseq.h>
#else
        #ifndef _GNU_SOURCE
        #error kernel_private requires gnu_source
        #endif
        #include <sched.h>
#endif
}

//-----------------------------------------------------------------------------
// Scheduler
extern "C" {
        void disable_interrupts() OPTIONAL_THREAD;
        void enable_interrupts( bool poll = true );
}

void schedule_thread$( thread$ * ) __attribute__((nonnull (1)));

extern bool __preemption_enabled();

//release/wake-up the following resources
void __thread_finish( thread$ * thrd );

//-----------------------------------------------------------------------------
// Hardware

#if   defined(CFA_HAVE_LINUX_LIBRSEQ)
        // No data needed
#elif defined(CFA_HAVE_LINUX_RSEQ_H)
        extern "Cforall" {
                extern __attribute__((aligned(128))) thread_local volatile struct rseq __cfaabi_rseq;
        }
#else
        // No data needed
#endif

static inline int __kernel_getcpu() {
        /* paranoid */ verify( ! __preemption_enabled() );
#if   defined(CFA_HAVE_LINUX_LIBRSEQ)
        return rseq_current_cpu();
#elif defined(CFA_HAVE_LINUX_RSEQ_H)
        int r = __cfaabi_rseq.cpu_id;
        /* paranoid */ verify( r >= 0 );
        return r;
#else
        return sched_getcpu();
#endif
}

//-----------------------------------------------------------------------------
// Processor
void main(processorCtx_t *);

void * __create_pthread( pthread_t *, void * (*)(void *), void * );
void __destroy_pthread( pthread_t pthread, void * stack, void ** retval );

extern cluster * mainCluster;

//-----------------------------------------------------------------------------
// Threads
extern "C" {
      void __cfactx_invoke_thread(void (*main)(void *), void * this);
}

__cfaabi_dbg_debug_do(
        extern void __cfaabi_dbg_thread_register  ( thread$ * thrd );
        extern void __cfaabi_dbg_thread_unregister( thread$ * thrd );
)

#define TICKET_BLOCKED (-1) // thread is blocked
#define TICKET_RUNNING ( 0) // thread is running
#define TICKET_UNBLOCK ( 1) // thread should ignore next block

//-----------------------------------------------------------------------------
// Utils
void doregister( struct cluster * cltr, struct thread$ & thrd );
void unregister( struct cluster * cltr, struct thread$ & thrd );

//-----------------------------------------------------------------------------
// I/O
$io_arbiter * create(void);
void destroy($io_arbiter *);

//=======================================================================
// Cluster lock API
//=======================================================================
// Lock-Free registering/unregistering of threads
// Register a processor to a given cluster and get its unique id in return
unsigned register_proc_id( void );

// Unregister a processor from a given cluster using its id, getting back the original pointer
void unregister_proc_id( unsigned );

//=======================================================================
// Reader-writer lock implementation
// Concurrent with doregister/unregister,
//    i.e., threads can be added at any point during or between the entry/exit

//-----------------------------------------------------------------------
// simple spinlock underlying the RWLock
// Blocking acquire
static inline void __atomic_acquire(volatile bool * ll) {
        while( __builtin_expect(__atomic_exchange_n(ll, (bool)true, __ATOMIC_SEQ_CST), false) ) {
                while(__atomic_load_n(ll, (int)__ATOMIC_RELAXED))
                        Pause();
        }
        /* paranoid */ verify(*ll);
}

// Non-Blocking acquire
static inline bool __atomic_try_acquire(volatile bool * ll) {
        return !__atomic_exchange_n(ll, (bool)true, __ATOMIC_SEQ_CST);
}

// Release
static inline void __atomic_unlock(volatile bool * ll) {
        /* paranoid */ verify(*ll);
        __atomic_store_n(ll, (bool)false, __ATOMIC_RELEASE);
}





//-----------------------------------------------------------------------
// Reader-Writer lock protecting the ready-queues
// while this lock is mostly generic some aspects
// have been hard-coded to for the ready-queue for
// simplicity and performance
struct __scheduler_RWLock_t {
        // total cachelines allocated
        unsigned int max;

        // cachelines currently in use
        volatile unsigned int alloc;

        // cachelines ready to itereate over
        // (!= to alloc when thread is in second half of doregister)
        volatile unsigned int ready;

        // writer lock
        volatile bool write_lock;

        // data pointer
        volatile bool * volatile * data;
};

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

extern __scheduler_RWLock_t * __scheduler_lock;

//-----------------------------------------------------------------------
// Reader side : acquire when using the ready queue to schedule but not
//  creating/destroying queues
static inline void ready_schedule_lock(void) with(*__scheduler_lock) {
        /* paranoid */ verify( ! __preemption_enabled() );
        /* paranoid */ verify( ! kernelTLS().in_sched_lock );
        /* paranoid */ verify( data[kernelTLS().sched_id] == &kernelTLS().sched_lock );
        /* paranoid */ verify( !kernelTLS().this_processor || kernelTLS().this_processor->unique_id == kernelTLS().sched_id );

        // Step 1 : make sure no writer are in the middle of the critical section
        while(__atomic_load_n(&write_lock, (int)__ATOMIC_RELAXED))
                Pause();

        // Fence needed because we don't want to start trying to acquire the lock
        // before we read a false.
        // Not needed on x86
        // std::atomic_thread_fence(std::memory_order_seq_cst);

        // Step 2 : acquire our local lock
        __atomic_acquire( &kernelTLS().sched_lock );
        /*paranoid*/ verify(kernelTLS().sched_lock);

        #ifdef __CFA_WITH_VERIFY__
                // Debug, check if this is owned for reading
                kernelTLS().in_sched_lock = true;
        #endif
}

static inline void ready_schedule_unlock(void) with(*__scheduler_lock) {
        /* paranoid */ verify( ! __preemption_enabled() );
        /* paranoid */ verify( data[kernelTLS().sched_id] == &kernelTLS().sched_lock );
        /* paranoid */ verify( !kernelTLS().this_processor || kernelTLS().this_processor->unique_id == kernelTLS().sched_id );
        /* paranoid */ verify( kernelTLS().sched_lock );
        /* paranoid */ verify( kernelTLS().in_sched_lock );
        #ifdef __CFA_WITH_VERIFY__
                // Debug, check if this is owned for reading
                kernelTLS().in_sched_lock = false;
        #endif
        __atomic_unlock(&kernelTLS().sched_lock);
}

#ifdef __CFA_WITH_VERIFY__
        static inline bool ready_schedule_islocked(void) {
                /* paranoid */ verify( ! __preemption_enabled() );
                /* paranoid */ verify( (!kernelTLS().in_sched_lock) || kernelTLS().sched_lock );
                return kernelTLS().sched_lock;
        }

        static inline bool ready_mutate_islocked() {
                return __scheduler_lock->write_lock;
        }
#endif

//-----------------------------------------------------------------------
// Writer side : acquire when changing the ready queue, e.g. adding more
//  queues or removing them.
uint_fast32_t ready_mutate_lock( void );

void ready_mutate_unlock( uint_fast32_t /* value returned by lock */ );

//-----------------------------------------------------------------------
// Lock-Free registering/unregistering of threads
// Register a processor to a given cluster and get its unique id in return
// For convenience, also acquires the lock
static inline [unsigned, uint_fast32_t] ready_mutate_register() {
        unsigned id = register_proc_id();
        uint_fast32_t last = ready_mutate_lock();
        return [id, last];
}

// Unregister a processor from a given cluster using its id, getting back the original pointer
// assumes the lock is acquired
static inline void ready_mutate_unregister( unsigned id, uint_fast32_t last_s ) {
        ready_mutate_unlock( last_s );
        unregister_proc_id( id );
}

//-----------------------------------------------------------------------
// Cluster idle lock/unlock
static inline void lock(__cluster_proc_list & this) {
        /* paranoid */ verify( ! __preemption_enabled() );

        // Start by locking the global RWlock so that we know no-one is
        // adding/removing processors while we mess with the idle lock
        ready_schedule_lock();

        // Simple counting lock, acquired, acquired by incrementing the counter
        // to an odd number
        for() {
                uint64_t l = this.lock;
                if(
                        (0 == (l % 2))
                        && __atomic_compare_exchange_n(&this.lock, &l, l + 1, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)
                ) return;
                Pause();
        }

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

static inline void unlock(__cluster_proc_list & this) {
        /* paranoid */ verify( ! __preemption_enabled() );

        /* paranoid */ verify( 1 == (this.lock % 2) );
        // Simple couting lock, release by incrementing to an even number
        __atomic_fetch_add( &this.lock, 1, __ATOMIC_SEQ_CST );

        // Release the global lock, which we acquired when locking
        ready_schedule_unlock();

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

//=======================================================================
// Ready-Queue API
//-----------------------------------------------------------------------
// push thread onto a ready queue for a cluster
// returns true if the list was previously empty, false otherwise
__attribute__((hot)) void push(struct cluster * cltr, struct thread$ * thrd, bool local);

//-----------------------------------------------------------------------
// pop thread from the local queues of a cluster
// returns 0p if empty
// May return 0p spuriously
__attribute__((hot)) struct thread$ * pop_fast(struct cluster * cltr);

//-----------------------------------------------------------------------
// pop thread from any ready queue of a cluster
// returns 0p if empty
// May return 0p spuriously
__attribute__((hot)) struct thread$ * pop_slow(struct cluster * cltr);

//-----------------------------------------------------------------------
// search all ready queues of a cluster for any thread
// returns 0p if empty
// guaranteed to find any threads added before this call
__attribute__((hot)) struct thread$ * pop_search(struct cluster * cltr);

//-----------------------------------------------------------------------
// Increase the width of the ready queue (number of lanes) by 4
void ready_queue_grow  (struct cluster * cltr);

//-----------------------------------------------------------------------
// Decrease the width of the ready queue (number of lanes) by 4
void ready_queue_shrink(struct cluster * cltr);


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