Changes in src/libcfa/concurrency/preemption.c [c5ac6d5:969b3fe]

File:

• src/libcfa/concurrency/preemption.c (modified) (3 diffs)

src/libcfa/concurrency/preemption.c

@@ -15 +15 @@
 //
 
+#include "libhdr.h"
 #include "preemption.h"
 
 extern "C" {
+#include <errno.h>
+#include <execinfo.h>
+#define __USE_GNU
 #include <signal.h>
-}
-
-#define __CFA_DEFAULT_PREEMPTION__ 10
-
+#undef __USE_GNU
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+}
+
+
+#ifdef __USE_STREAM__
+#include "fstream"
+#endif
+
+//TODO move to defaults
+#define __CFA_DEFAULT_PREEMPTION__ 10000
+
+//TODO move to defaults
 __attribute__((weak)) unsigned int default_preemption() {
         return __CFA_DEFAULT_PREEMPTION__;
 }
 
+// Short hands for signal context information
+#define __CFA_SIGCXT__ ucontext_t *
+#define __CFA_SIGPARMS__ __attribute__((unused)) int sig, __attribute__((unused)) siginfo_t *sfp, __attribute__((unused)) __CFA_SIGCXT__ cxt
+
+// FwdDeclarations : timeout handlers
 static void preempt( processor   * this );
 static void timeout( thread_desc * this );
 
+// FwdDeclarations : Signal handlers
+void sigHandler_ctxSwitch( __CFA_SIGPARMS__ );
+void sigHandler_segv     ( __CFA_SIGPARMS__ );
+void sigHandler_abort    ( __CFA_SIGPARMS__ );
+
+// FwdDeclarations : sigaction wrapper
+static void __kernel_sigaction( int sig, void (*handler)(__CFA_SIGPARMS__), int flags );
+
+// FwdDeclarations : alarm thread main
+void * alarm_loop( __attribute__((unused)) void * args );
+
+// Machine specific register name
+#ifdef __x86_64__
+#define CFA_REG_IP REG_RIP
+#else
+#define CFA_REG_IP REG_EIP
+#endif
+
+KERNEL_STORAGE(event_kernel_t, event_kernel);         // private storage for event kernel
+event_kernel_t * event_kernel;                        // kernel public handle to even kernel
+static pthread_t alarm_thread;                        // pthread handle to alarm thread
+
+void ?{}(event_kernel_t * this) {
+        (&this->alarms){};
+        (&this->lock){};
+}
+
 //=============================================================================================
 // Kernel Preemption logic
 //=============================================================================================
 
-void kernel_start_preemption() {
-
-}
-
+// Get next expired node
+static inline alarm_node_t * get_expired( alarm_list_t * alarms, __cfa_time_t currtime ) {
+        if( !alarms->head ) return NULL;                          // If no alarms return null
+        if( alarms->head->alarm >= currtime ) return NULL;        // If alarms head not expired return null
+        return pop(alarms);                                       // Otherwise just pop head
+}
+
+// Tick one frame of the Discrete Event Simulation for alarms
 void tick_preemption() {
-        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);
+        alarm_node_t * node = NULL;                     // Used in the while loop but cannot be declared in the while condition
+        alarm_list_t * alarms = &event_kernel->alarms;  // Local copy for ease of reading
+        __cfa_time_t currtime = __kernel_get_time();    // Check current time once so we everything "happens at once"
+
+        //Loop throught every thing expired
+        while( node = get_expired( alarms, currtime ) ) {
+
+                // Check if this is a kernel
                 if( node->kernel_alarm ) {
                         preempt( node->proc );
@@ -50 +105 @@
                 }
 
-                if( node->period > 0 ) {
-                        node->alarm += node->period;
-                        insert( alarms, node );
+                // Check if this is a periodic alarm
+                __cfa_time_t period = node->period;
+                if( period > 0 ) {
+                        node->alarm = currtime + period;    // Alarm is periodic, add currtime to it (used cached current time)
+                        insert( alarms, node );             // Reinsert the node for the next time it triggers
                 }
                 else {
-                        node->set = false;
-                }
-        }
-
-        if( alarms->head ) {
-                __kernel_set_timer( alarms->head->alarm - currtime );
-        }
-}
-
+                        node->set = false;                  // Node is one-shot, just mark it as not pending
+                }
+        }
+
+        // If there are still alarms pending, reset the timer
+        if( alarms->head ) { __kernel_set_timer( alarms->head->alarm - currtime ); }
+}
+
+// Update the preemption of a processor and notify interested parties
 void update_preemption( processor * this, __cfa_time_t duration ) {
-        //     assert( THREAD_GETMEM( disableInt ) && THREAD_GETMEM( disableIntCnt ) == 1 );
         alarm_node_t * alarm = this->preemption_alarm;
 
@@ -89 +145 @@
 }
 
+//=============================================================================================
+// Kernel Signal Tools
+//=============================================================================================
+
+LIB_DEBUG_DO( static thread_local void * last_interrupt = 0; )
+
+extern "C" {
+        // Disable interrupts by incrementing the counter
+        void disable_interrupts() {
+                __attribute__((unused)) unsigned short new_val = __atomic_add_fetch_2( &disable_preempt_count, 1, __ATOMIC_SEQ_CST );
+                verify( new_val < 65_000u );              // If this triggers someone is disabling interrupts without enabling them
+        }
+
+        // Enable interrupts by decrementing the counter
+        // If counter reaches 0, execute any pending CtxSwitch
+        void enable_interrupts( DEBUG_CTX_PARAM ) {
+                processor * proc   = this_processor;      // Cache the processor now since interrupts can start happening after the atomic add
+                thread_desc * thrd = this_thread;         // Cache the thread now since interrupts can start happening after the atomic add
+
+                unsigned short prev = __atomic_fetch_add_2( &disable_preempt_count, -1, __ATOMIC_SEQ_CST );
+                verify( prev != 0u );                     // If this triggers someone is enabled already enabled interruptsverify( prev != 0u );
+
+                // Check if we need to prempt the thread because an interrupt was missed
+                if( prev == 1 && proc->pending_preemption ) {
+                        proc->pending_preemption = false;
+                        BlockInternal( thrd );
+                }
+
+                // For debugging purposes : keep track of the last person to enable the interrupts
+                LIB_DEBUG_DO( proc->last_enable = caller; )
+        }
+
+        // Disable interrupts by incrementint the counter
+        // Don't execute any pending CtxSwitch even if counter reaches 0
+        void enable_interrupts_noPoll() {
+                __attribute__((unused)) unsigned short prev = __atomic_fetch_add_2( &disable_preempt_count, -1, __ATOMIC_SEQ_CST );
+                verify( prev != 0u );                     // If this triggers someone is enabled already enabled interrupts
+        }
+}
+
+// sigprocmask wrapper : unblock a single signal
+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" );
+        }
+}
+
+// sigprocmask wrapper : block a single signal
+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" );
+        }
+}
+
+// kill wrapper : signal a processor
+static void preempt( processor * this ) {
+        pthread_kill( this->kernel_thread, SIGUSR1 );
+}
+
+// reserved for future use
+static void timeout( thread_desc * this ) {
+        //TODO : implement waking threads
+}
+
+
+// Check if a CtxSwitch signal handler shoud defer
+// If true  : preemption is safe
+// If false : preemption is unsafe and marked as pending
+static inline bool preemption_ready() {
+        bool ready = disable_preempt_count == 0 && !preemption_in_progress; // Check if preemption is safe
+        this_processor->pending_preemption = !ready;                        // Adjust the pending flag accordingly
+        return ready;
+}
+
+//=============================================================================================
+// Kernel Signal Startup/Shutdown logic
+//=============================================================================================
+
+// Startup routine to activate preemption
+// Called from kernel_startup
+void kernel_start_preemption() {
+        LIB_DEBUG_PRINT_SAFE("Kernel : Starting preemption\n");
+
+        // Start with preemption disabled until ready
+        disable_preempt_count = 1;
+
+        // Initialize the event kernel
+        event_kernel = (event_kernel_t *)&storage_event_kernel;
+        event_kernel{};
+
+        // Setup proper signal handlers
+        __kernel_sigaction( SIGUSR1, sigHandler_ctxSwitch, SA_SIGINFO );         // CtxSwitch handler
+        // __kernel_sigaction( SIGSEGV, sigHandler_segv     , SA_SIGINFO );      // Failure handler
+        // __kernel_sigaction( SIGBUS , sigHandler_segv     , SA_SIGINFO );      // Failure handler
+
+        signal_block( SIGALRM );
+
+        pthread_create( &alarm_thread, NULL, alarm_loop, NULL );
+}
+
+// Shutdown routine to deactivate preemption
+// Called from kernel_shutdown
+void kernel_stop_preemption() {
+        LIB_DEBUG_PRINT_SAFE("Kernel : Preemption stopping\n");
+
+        // Block all signals since we are already shutting down
+        sigset_t mask;
+        sigfillset( &mask );
+        sigprocmask( SIG_BLOCK, &mask, NULL );
+
+        // Notify the alarm thread of the shutdown
+        sigval val = { 1 };
+        pthread_sigqueue( alarm_thread, SIGALRM, val );
+
+        // Wait for the preemption thread to finish
+        pthread_join( alarm_thread, NULL );
+
+        // Preemption is now fully stopped
+
+        LIB_DEBUG_PRINT_SAFE("Kernel : Preemption stopped\n");
+}
+
+// Raii ctor/dtor for the preemption_scope
+// Used by thread to control when they want to receive preemption signals
 void ?{}( preemption_scope * this, processor * proc ) {
-        (&this->alarm){ proc };
+        (&this->alarm){ proc, zero_time, zero_time };
         this->proc = proc;
         this->proc->preemption_alarm = &this->alarm;
-        update_preemption( this->proc, this->proc->preemption );
+
+        update_preemption( this->proc, from_us(this->proc->cltr->preemption) );
 }
 
 void ^?{}( preemption_scope * this ) {
-        update_preemption( this->proc, 0 );
-}
-
-//=============================================================================================
-// Kernel Signal logic
-//=============================================================================================
-
-static inline bool preemption_ready() {
-        return this_processor->disable_preempt_count == 0;
-}
-
-static inline void defer_ctxSwitch() {
-        this_processor->pending_preemption = true;
-}
-
-static inline void defer_alarm() {
-        systemProcessor->pending_alarm = true;
-}
-
-void sigHandler_ctxSwitch( __attribute__((unused)) int sig ) {
-        if( preemption_ready() ) {
-                ScheduleInternal( this_processor->current_thread );
-        }
-        else {
-                defer_ctxSwitch();
-        }
-}
-
-void sigHandler_alarm( __attribute__((unused)) int sig ) {
-        if( try_lock( &systemProcessor->alarm_lock ) ) {
-                tick_preemption();
-                unlock( &systemProcessor->alarm_lock );
-        }
-        else {
-                defer_alarm();
-        }
-}
-
-static void preempt( processor * this ) {
-        pthread_kill( this->kernel_thread, SIGUSR1 );
-}
-
-static void timeout( thread_desc * this ) {
-        //TODO : implement waking threads
-}
+        disable_interrupts();
+
+        update_preemption( this->proc, zero_time );
+}
+
+//=============================================================================================
+// Kernel Signal Handlers
+//=============================================================================================
+
+// Context switch signal handler
+// Receives SIGUSR1 signal and causes the current thread to yield
+void sigHandler_ctxSwitch( __CFA_SIGPARMS__ ) {
+        LIB_DEBUG_DO( last_interrupt = (void *)(cxt->uc_mcontext.gregs[CFA_REG_IP]); )
+
+        // Check if it is safe to preempt here
+        if( !preemption_ready() ) { return; }
+
+        preemption_in_progress = true;                      // Sync flag : prevent recursive calls to the signal handler
+        signal_unblock( SIGUSR1 );                          // We are about to CtxSwitch out of the signal handler, let other handlers in
+        preemption_in_progress = false;                     // Clear the in progress flag
+
+        // Preemption can occur here
+
+        BlockInternal( (thread_desc*)this_thread );         // Do the actual CtxSwitch
+}
+
+// Main of the alarm thread
+// Waits on SIGALRM and send SIGUSR1 to whom ever needs it
+void * alarm_loop( __attribute__((unused)) void * args ) {
+        // Block sigalrms to control when they arrive
+        sigset_t mask;
+        sigemptyset( &mask );
+        sigaddset( &mask, SIGALRM );
+
+        if ( pthread_sigmask( SIG_BLOCK, &mask, NULL ) == -1 ) {
+            abortf( "internal error, pthread_sigmask" );
+        }
+
+        // Main loop
+        while( true ) {
+                // Wait for a sigalrm
+                siginfo_t info;
+                int sig = sigwaitinfo( &mask, &info );
+
+                // If another signal arrived something went wrong
+                assertf(sig == SIGALRM, "Kernel Internal Error, sigwait: Unexpected signal %d (%d : %d)\n", sig, info.si_code, info.si_value.sival_int);
+
+                LIB_DEBUG_PRINT_SAFE("Kernel : Caught alarm from %d with %d\n", info.si_code, info.si_value.sival_int );
+                // Switch on the code (a.k.a. the sender) to
+                switch( info.si_code )
+                {
+                // Timers can apparently be marked as sent for the kernel
+                // In either case, tick preemption
+                case SI_TIMER:
+                case SI_KERNEL:
+                        LIB_DEBUG_PRINT_SAFE("Kernel : Preemption thread tick\n");
+                        lock( &event_kernel->lock DEBUG_CTX2 );
+                        tick_preemption();
+                        unlock( &event_kernel->lock );
+                        break;
+                // Signal was not sent by the kernel but by an other thread
+                case SI_QUEUE:
+                        // For now, other thread only signal the alarm thread to shut it down
+                        // If this needs to change use info.si_value and handle the case here
+                        goto EXIT;
+                }
+        }
+
+EXIT:
+        LIB_DEBUG_PRINT_SAFE("Kernel : Preemption thread stopping\n");
+        return NULL;
+}
+
+// Sigaction wrapper : register an signal handler
+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 );
+        }
+}
+
+// Sigaction wrapper : restore default handler
+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 );
+// }