source: src/libcfa/concurrency/preemption.c@ 4fbdfae0

//                              -*- Mode: CFA -*-
//
// 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.
//
// signal.c --
//
// Author           : Thierry Delisle
// Created On       : Mon Jun 5 14:20:42 2017
// Last Modified By : Thierry Delisle
// Last Modified On : --
// Update Count     : 0
//

#include "libhdr.h"
#include "preemption.h"

extern "C" {
#include <errno.h>
#include <execinfo.h>
#define __USE_GNU
#include <signal.h>
#undef __USE_GNU
#include <stdio.h>
#include <string.h>
#include <unistd.h>
}


#ifdef __USE_STREAM__
#include "fstream"
#endif

#define __CFA_DEFAULT_PREEMPTION__ 10000

__attribute__((weak)) unsigned int default_preemption() {
        return __CFA_DEFAULT_PREEMPTION__;
}

#define __CFA_SIGCXT__ ucontext_t *
#define __CFA_SIGPARMS__ __attribute__((unused)) int sig, __attribute__((unused)) siginfo_t *sfp, __attribute__((unused)) __CFA_SIGCXT__ cxt

static void preempt( processor   * this );
static void timeout( thread_desc * this );

void sigHandler_ctxSwitch( __CFA_SIGPARMS__ );
void sigHandler_alarm    ( __CFA_SIGPARMS__ );
void sigHandler_segv     ( __CFA_SIGPARMS__ );
void sigHandler_abort    ( __CFA_SIGPARMS__ );

static void __kernel_sigaction( int sig, void (*handler)(__CFA_SIGPARMS__), int flags );
LIB_DEBUG_DO( bool validate( alarm_list_t * this ); )

#ifdef __x86_64__
#define CFA_REG_IP REG_RIP
#else
#define CFA_REG_IP REG_EIP
#endif


//=============================================================================================
// Kernel Preemption logic
//=============================================================================================

void tick_preemption() {
        // LIB_DEBUG_PRINT_BUFFER_DECL( STDERR_FILENO, "Ticking preemption\n" );

        alarm_list_t * alarms = &systemProcessor->alarms;
        __cfa_time_t currtime = __kernel_get_time();
        while( alarms->head && alarms->head->alarm < currtime ) {
                alarm_node_t * node = pop(alarms);
                // LIB_DEBUG_PRINT_BUFFER_LOCAL( STDERR_FILENO, "Ticking %p\n", node );

                if( node->kernel_alarm ) {
                        preempt( node->proc );
                }
                else {
                        timeout( node->thrd );
                }

                verify( validate( alarms ) );

                if( node->period > 0 ) {
                        node->alarm = currtime + node->period;
                        insert( alarms, node );
                }
                else {
                        node->set = false;
                }
        }

        if( alarms->head ) {
                __kernel_set_timer( alarms->head->alarm - currtime );
        }

        verify( validate( alarms ) );
        // LIB_DEBUG_PRINT_BUFFER_LOCAL( STDERR_FILENO, "Ticking preemption done\n" );
}

void update_preemption( processor * this, __cfa_time_t duration ) {
        LIB_DEBUG_PRINT_BUFFER_DECL( STDERR_FILENO, "Processor : %p updating preemption to %lu\n", this, duration );

        alarm_node_t * alarm = this->preemption_alarm;
        duration *= 1000;

        // Alarms need to be enabled
        if ( duration > 0 && !alarm->set ) {
                alarm->alarm = __kernel_get_time() + duration;
                alarm->period = duration;
                register_self( alarm );
        }
        // Zero duraction but alarm is set
        else if ( duration == 0 && alarm->set ) {
                unregister_self( alarm );
                alarm->alarm = 0;
                alarm->period = 0;
        }
        // If alarm is different from previous, change it
        else if ( duration > 0 && alarm->period != duration ) {
                unregister_self( alarm );
                alarm->alarm = __kernel_get_time() + duration;
                alarm->period = duration;
                register_self( alarm );
        }
}

//=============================================================================================
// Kernel Signal Tools
//=============================================================================================

LIB_DEBUG_DO( static thread_local void * last_interrupt = 0; )

extern "C" {
        void disable_interrupts() {
                __attribute__((unused)) unsigned short new_val = __atomic_add_fetch_2( &disable_preempt_count, 1, __ATOMIC_SEQ_CST );
                verify( new_val < (unsigned short)65_000 );
                verify( new_val != (unsigned short) 0 );
        }

        void enable_interrupts_noRF() {
                __attribute__((unused)) unsigned short prev = __atomic_fetch_add_2( &disable_preempt_count, -1, __ATOMIC_SEQ_CST );
                verify( prev != (unsigned short) 0 );
        }

        void enable_interrupts( DEBUG_CTX_PARAM ) {
                processor * proc   = this_processor;
                thread_desc * thrd = this_thread;
                unsigned short prev = __atomic_fetch_add_2( &disable_preempt_count, -1, __ATOMIC_SEQ_CST );
                verify( prev != (unsigned short) 0 );
                if( prev == 1 && proc->pending_preemption ) {
                        proc->pending_preemption = false;
                        BlockInternal( thrd );
                }

                LIB_DEBUG_DO( proc->last_enable = caller; )
        }
}

static inline void signal_unblock( int sig ) {
        sigset_t mask;
        sigemptyset( &mask );
        sigaddset( &mask, sig );

        if ( pthread_sigmask( SIG_UNBLOCK, &mask, NULL ) == -1 ) {
            abortf( "internal error, pthread_sigmask" );
        }
}

static inline void signal_block( int sig ) {
        sigset_t mask;
        sigemptyset( &mask );
        sigaddset( &mask, sig );

        if ( pthread_sigmask( SIG_BLOCK, &mask, NULL ) == -1 ) {
            abortf( "internal error, pthread_sigmask" );
        }
}

static inline bool preemption_ready() {
        return disable_preempt_count == 0 && !preemption_in_progress;
}

static inline void defer_ctxSwitch() {
        this_processor->pending_preemption = true;
}

static inline void defer_alarm() {
        systemProcessor->pending_alarm = true;
}

static void preempt( processor * this ) {
        pthread_kill( this->kernel_thread, SIGUSR1 );
}

static void timeout( thread_desc * this ) {
        //TODO : implement waking threads
}

//=============================================================================================
// Kernel Signal Startup/Shutdown logic
//=============================================================================================

static pthread_t alarm_thread;
void * alarm_loop( __attribute__((unused)) void * args );

void kernel_start_preemption() {
        LIB_DEBUG_PRINT_SAFE("Kernel : Starting preemption\n");
        __kernel_sigaction( SIGUSR1, sigHandler_ctxSwitch, SA_SIGINFO );
        // __kernel_sigaction( SIGSEGV, sigHandler_segv     , SA_SIGINFO );
        // __kernel_sigaction( SIGBUS , sigHandler_segv     , SA_SIGINFO );

        signal_block( SIGALRM );

        pthread_create( &alarm_thread, NULL, alarm_loop, NULL );
}

void kernel_stop_preemption() {
        LIB_DEBUG_PRINT_SAFE("Kernel : Preemption stopping\n");

        sigset_t mask;
        sigfillset( &mask );
        sigprocmask( SIG_BLOCK, &mask, NULL );

        sigval val = { 1 };
        pthread_sigqueue( alarm_thread, SIGALRM, val );
        pthread_join( alarm_thread, NULL );
        LIB_DEBUG_PRINT_SAFE("Kernel : Preemption stopped\n");
}

void ?{}( preemption_scope & this, processor * proc ) {
        (this.alarm){ proc };
        this.proc = proc;
        this.proc->preemption_alarm = &this.alarm;
        update_preemption( this.proc, this.proc->preemption );
}

void ^?{}( preemption_scope & this ) {
        disable_interrupts();

        update_preemption( this.proc, 0 );
}

//=============================================================================================
// Kernel Signal Handlers
//=============================================================================================

void sigHandler_ctxSwitch( __CFA_SIGPARMS__ ) {
        LIB_DEBUG_DO( last_interrupt = (void *)(cxt->uc_mcontext.gregs[CFA_REG_IP]); )
        if( preemption_ready() ) {
                preemption_in_progress = true;
                signal_unblock( SIGUSR1 );
                this_processor->pending_preemption = false;
                preemption_in_progress = false;
                BlockInternal( (thread_desc*)this_thread );
        }
        else {
                defer_ctxSwitch();
        }
}

void * alarm_loop( __attribute__((unused)) void * args ) {
        sigset_t mask;
        sigemptyset( &mask );
        sigaddset( &mask, SIGALRM );

        if ( pthread_sigmask( SIG_BLOCK, &mask, NULL ) == -1 ) {
            abortf( "internal error, pthread_sigmask" );
        }

        while( true ) {
                siginfo_t info;
                int sig = sigwaitinfo( &mask, &info );
                if( sig < 0 ) {
                        abortf( "internal error, sigwait" );
                }
                else if( sig == SIGALRM )
                {
                        LIB_DEBUG_PRINT_SAFE("Kernel : Caught signal %d (%d)\n", sig, info.si_value.sival_int );
                        if( info.si_value.sival_int == 0 )
                        {
                                LIB_DEBUG_PRINT_SAFE("Kernel : Preemption thread tick\n");
                                lock( &systemProcessor->alarm_lock DEBUG_CTX2 );
                                tick_preemption();
                                unlock( &systemProcessor->alarm_lock );
                        }
                        else if( info.si_value.sival_int == 1 )
                        {
                                break;
                        }
                }
                else
                {
                        LIB_DEBUG_PRINT_SAFE("Kernel : Unexpected signal %d (%d)\n", sig, info.si_value.sival_int);
                }
        }

        LIB_DEBUG_PRINT_SAFE("Kernel : Preemption thread stopping\n");
        return NULL;
}

static void __kernel_sigaction( int sig, void (*handler)(__CFA_SIGPARMS__), int flags ) {
        struct sigaction act;

        act.sa_sigaction = (void (*)(int, siginfo_t *, void *))handler;
        act.sa_flags = flags;

        if ( sigaction( sig, &act, NULL ) == -1 ) {
                LIB_DEBUG_PRINT_BUFFER_DECL( STDERR_FILENO,
                        " __kernel_sigaction( sig:%d, handler:%p, flags:%d ), problem installing signal handler, error(%d) %s.\n",
                        sig, handler, flags, errno, strerror( errno )
                );
                _exit( EXIT_FAILURE );
        }
}

typedef void (*sa_handler_t)(int);

static void __kernel_sigdefault( int sig ) {
        struct sigaction act;

        // act.sa_handler = SIG_DFL;
        act.sa_flags = 0;
        sigemptyset( &act.sa_mask );

        if ( sigaction( sig, &act, NULL ) == -1 ) {
                LIB_DEBUG_PRINT_BUFFER_DECL( STDERR_FILENO,
                        " __kernel_sigdefault( sig:%d ), problem reseting signal handler, error(%d) %s.\n",
                        sig, errno, strerror( errno )
                );
                _exit( EXIT_FAILURE );
        }
}

//=============================================================================================
// Terminating Signals logic
//=============================================================================================

LIB_DEBUG_DO(
        static void __kernel_backtrace( int start ) {
                // skip first N stack frames

                enum { Frames = 50 };
                void * array[Frames];
                int size = backtrace( array, Frames );
                char ** messages = backtrace_symbols( array, size );

                // find executable name
                *index( messages[0], '(' ) = '\0';
                #ifdef __USE_STREAM__
                serr | "Stack back trace for:" | messages[0] | endl;
                #else
                fprintf( stderr, "Stack back trace for: %s\n", messages[0]);
                #endif

                // skip last 2 stack frames after main
                for ( int i = start; i < size && messages != NULL; i += 1 ) {
                        char * name = NULL;
                        char * offset_begin = NULL;
                        char * offset_end = NULL;

                        for ( char *p = messages[i]; *p; ++p ) {
                                // find parantheses and +offset
                                if ( *p == '(' ) {
                                        name = p;
                                }
                                else if ( *p == '+' ) {
                                        offset_begin = p;
                                }
                                else if ( *p == ')' ) {
                                        offset_end = p;
                                        break;
                                }
                        }

                        // if line contains symbol print it
                        int frameNo = i - start;
                        if ( name && offset_begin && offset_end && name < offset_begin ) {
                                // delimit strings
                                *name++ = '\0';
                                *offset_begin++ = '\0';
                                *offset_end++ = '\0';

                                #ifdef __USE_STREAM__
                                serr    | "("  | frameNo | ")" | messages[i] | ":"
                                        | name | "+" | offset_begin | offset_end | endl;
                                #else
                                fprintf( stderr, "(%i) %s : %s + %s %s\n", frameNo, messages[i], name, offset_begin, offset_end);
                                #endif
                        }
                        // otherwise, print the whole line
                        else {
                                #ifdef __USE_STREAM__
                                serr | "(" | frameNo | ")" | messages[i] | endl;
                                #else
                                fprintf( stderr, "(%i) %s\n", frameNo, messages[i] );
                                #endif
                        }
                }

                free( messages );
        }
)

// void sigHandler_segv( __CFA_SIGPARMS__ ) {
//      LIB_DEBUG_DO(
//              #ifdef __USE_STREAM__
//              serr    | "*CFA runtime error* program cfa-cpp terminated with"
//                      | (sig == SIGSEGV ? "segment fault." : "bus error.")
//                      | endl;
//              #else
//              fprintf( stderr, "*CFA runtime error* program cfa-cpp terminated with %s\n", sig == SIGSEGV ? "segment fault." : "bus error." );
//              #endif

//              // skip first 2 stack frames
//              __kernel_backtrace( 1 );
//      )
//      exit( EXIT_FAILURE );
// }

// void sigHandler_abort( __CFA_SIGPARMS__ ) {
//      // skip first 6 stack frames
//      LIB_DEBUG_DO( __kernel_backtrace( 6 ); )

//      // reset default signal handler
//      __kernel_sigdefault( SIGABRT );

//      raise( SIGABRT );
// }