Changeset 21a5dde1 for src/libcfa

Timestamp:

Jul 20, 2017, 11:33:59 PM (7 years ago)

Author:

Peter A. Buhr <pabuhr@…>

Branches:

ADT, aaron-thesis, arm-eh, ast-experimental, cleanup-dtors, deferred_resn, demangler, enum, forall-pointer-decay, jacob/cs343-translation, jenkins-sandbox, master, new-ast, new-ast-unique-expr, new-env, no_list, persistent-indexer, pthread-emulation, qualifiedEnum, resolv-new, with_gc

Children:

6d54c3a

Parents:

dab7ac7 (diff), e1e4aa9 (diff)
Note: this is a merge changeset, the changes displayed below correspond to the merge itself.
Use the (diff) links above to see all the changes relative to each parent.

Message:

Merge branch 'master' of plg2:software/cfa/cfa-cc

Location:

src/libcfa/concurrency

Files:

• alarm.c (modified) (6 diffs)
• alarm.h (modified) (2 diffs)
• coroutine (modified) (1 diff)
• coroutine.c (modified) (1 diff)
• kernel (modified) (3 diffs)
• kernel.c (modified) (14 diffs)
• kernel_private.h (modified) (4 diffs)
• preemption.c (modified) (14 diffs)
• thread (modified) (1 diff)
• thread.c (modified) (1 diff)

src/libcfa/concurrency/alarm.c

@@ -31 +31 @@
 
 //=============================================================================================
+// time type
+//=============================================================================================
+
+#define one_second         1_000_000_000ul
+#define one_milisecond         1_000_000ul
+#define one_microsecond            1_000ul
+#define one_nanosecond                 1ul
+
+__cfa_time_t zero_time = { 0 };
+
+void ?{}( __cfa_time_t * this ) { this->val = 0; }
+void ?{}( __cfa_time_t * this, zero_t zero ) { this->val = 0; }
+
+void ?{}( itimerval * this, __cfa_time_t * alarm ) {
+        this->it_value.tv_sec = alarm->val / one_second;                        // seconds
+        this->it_value.tv_usec = max( (alarm->val % one_second) / one_microsecond, 1000 ); // microseconds
+        this->it_interval.tv_sec = 0;
+        this->it_interval.tv_usec = 0;
+}
+
+
+void ?{}( __cfa_time_t * this, timespec * curr ) {
+        uint64_t secs  = curr->tv_sec;
+        uint64_t nsecs = curr->tv_nsec;
+        this->val = (secs * one_second) + nsecs;
+}
+
+__cfa_time_t ?=?( __cfa_time_t * this, zero_t rhs ) {
+        this->val = 0;
+        return *this;
+}
+
+__cfa_time_t from_s ( uint64_t val ) { __cfa_time_t ret; ret.val = val * 1_000_000_000ul; return ret; }
+__cfa_time_t from_ms( uint64_t val ) { __cfa_time_t ret; ret.val = val *     1_000_000ul; return ret; }
+__cfa_time_t from_us( uint64_t val ) { __cfa_time_t ret; ret.val = val *         1_000ul; return ret; }
+__cfa_time_t from_ns( uint64_t val ) { __cfa_time_t ret; ret.val = val *             1ul; return ret; }
+
+//=============================================================================================
 // Clock logic
 //=============================================================================================
@@ -37 +75 @@
         timespec curr;
         clock_gettime( CLOCK_REALTIME, &curr );
-        __cfa_time_t curr_time = ((__cfa_time_t)curr.tv_sec * TIMEGRAN) + curr.tv_nsec;
-        // LIB_DEBUG_PRINT_BUFFER_DECL( STDERR_FILENO, "Kernel : current time is %lu\n", curr_time );
-        return curr_time;
+        return (__cfa_time_t){ &curr };
 }
 
 void __kernel_set_timer( __cfa_time_t alarm ) {
-        LIB_DEBUG_PRINT_BUFFER_DECL( STDERR_FILENO, "Kernel : set timer to %llu\n", (__cfa_time_t)alarm );
-        itimerval val;
-        val.it_value.tv_sec = alarm / TIMEGRAN;                 // seconds
-        val.it_value.tv_usec = max( (alarm % TIMEGRAN) / ( TIMEGRAN / 1_000_000L ), 1000 ); // microseconds
-        val.it_interval.tv_sec = 0;
-        val.it_interval.tv_usec = 0;
+        itimerval val = { &alarm };
         setitimer( ITIMER_REAL, &val, NULL );
 }
@@ -56 +87 @@
 //=============================================================================================
 
-void ?{}( alarm_node_t * this, thread_desc * thrd, __cfa_time_t alarm = 0, __cfa_time_t period = 0 ) {
+void ?{}( alarm_node_t * this, thread_desc * thrd, __cfa_time_t alarm = zero_time, __cfa_time_t period = zero_time ) {
         this->thrd = thrd;
         this->alarm = alarm;
@@ -65 +96 @@
 }
 
-void ?{}( alarm_node_t * this, processor   * proc, __cfa_time_t alarm = 0, __cfa_time_t period = 0 ) {
+void ?{}( alarm_node_t * this, processor   * proc, __cfa_time_t alarm = zero_time, __cfa_time_t period = zero_time ) {
         this->proc = proc;
         this->alarm = alarm;
@@ -153 +184 @@
 
 void register_self( alarm_node_t * this ) {
+        alarm_list_t * alarms = &event_kernel->alarms;
+
         disable_interrupts();
-        verify( !systemProcessor->pending_alarm );
-        lock( &systemProcessor->alarm_lock DEBUG_CTX2 );
+        lock( &event_kernel->lock DEBUG_CTX2 );
         {
-                verify( validate( &systemProcessor->alarms ) );
-                bool first = !systemProcessor->alarms.head;
-
-                insert( &systemProcessor->alarms, this );
-                if( systemProcessor->pending_alarm ) {
-                        tick_preemption();
+                verify( validate( alarms ) );
+                bool first = !alarms->head;
+
+                insert( alarms, this );
+                if( first ) {
+                        __kernel_set_timer( alarms->head->alarm - __kernel_get_time() );
                 }
-                if( first ) {
-                        __kernel_set_timer( systemProcessor->alarms.head->alarm - __kernel_get_time() );
-                }
-        }
-        unlock( &systemProcessor->alarm_lock );
+        }
+        unlock( &event_kernel->lock );
         this->set = true;
         enable_interrupts( DEBUG_CTX );
@@ -174 +203 @@
 
 void unregister_self( alarm_node_t * this ) {
-        // LIB_DEBUG_PRINT_BUFFER_DECL( STDERR_FILENO, "Kernel : unregister %p start\n", this );
         disable_interrupts();
-        lock( &systemProcessor->alarm_lock DEBUG_CTX2 );
+        lock( &event_kernel->lock DEBUG_CTX2 );
         {
-                verify( validate( &systemProcessor->alarms ) );
-                remove( &systemProcessor->alarms, this );
-        }
-        unlock( &systemProcessor->alarm_lock );
+                verify( validate( &event_kernel->alarms ) );
+                remove( &event_kernel->alarms, this );
+        }
+        unlock( &event_kernel->lock );
         enable_interrupts( DEBUG_CTX );
         this->set = false;
-        // LIB_DEBUG_PRINT_BUFFER_LOCAL( STDERR_FILENO, "Kernel : unregister %p end\n", this );
-}
+}

src/libcfa/concurrency/alarm.h

@@ -23 +23 @@
 #include <assert.h>
 
-typedef uint64_t __cfa_time_t;
-
 struct thread_desc;
 struct processor;
+
+struct timespec;
+struct itimerval;
+
+//=============================================================================================
+// time type
+//=============================================================================================
+
+struct __cfa_time_t {
+        uint64_t val;
+};
+
+// ctors
+void ?{}( __cfa_time_t * this );
+void ?{}( __cfa_time_t * this, zero_t zero );
+void ?{}( __cfa_time_t * this, timespec * curr );
+void ?{}( itimerval * this, __cfa_time_t * alarm );
+
+__cfa_time_t ?=?( __cfa_time_t * this, zero_t rhs );
+
+// logical ops
+static inline bool ?==?( __cfa_time_t lhs, __cfa_time_t rhs ) { return lhs.val == rhs.val; }
+static inline bool ?!=?( __cfa_time_t lhs, __cfa_time_t rhs ) { return lhs.val != rhs.val; }
+static inline bool ?>? ( __cfa_time_t lhs, __cfa_time_t rhs ) { return lhs.val >  rhs.val; }
+static inline bool ?<? ( __cfa_time_t lhs, __cfa_time_t rhs ) { return lhs.val <  rhs.val; }
+static inline bool ?>=?( __cfa_time_t lhs, __cfa_time_t rhs ) { return lhs.val >= rhs.val; }
+static inline bool ?<=?( __cfa_time_t lhs, __cfa_time_t rhs ) { return lhs.val <= rhs.val; }
+
+static inline bool ?==?( __cfa_time_t lhs, zero_t rhs ) { return lhs.val == rhs; }
+static inline bool ?!=?( __cfa_time_t lhs, zero_t rhs ) { return lhs.val != rhs; }
+static inline bool ?>? ( __cfa_time_t lhs, zero_t rhs ) { return lhs.val >  rhs; }
+static inline bool ?<? ( __cfa_time_t lhs, zero_t rhs ) { return lhs.val <  rhs; }
+static inline bool ?>=?( __cfa_time_t lhs, zero_t rhs ) { return lhs.val >= rhs; }
+static inline bool ?<=?( __cfa_time_t lhs, zero_t rhs ) { return lhs.val <= rhs; }
+
+// addition/substract
+static inline __cfa_time_t ?+?( __cfa_time_t lhs, __cfa_time_t rhs ) {
+        __cfa_time_t ret;
+        ret.val = lhs.val + rhs.val;
+        return ret;
+}
+
+static inline __cfa_time_t ?-?( __cfa_time_t lhs, __cfa_time_t rhs ) {
+        __cfa_time_t ret;
+        ret.val = lhs.val - rhs.val;
+        return ret;
+}
+
+__cfa_time_t from_s ( uint64_t );
+__cfa_time_t from_ms( uint64_t );
+__cfa_time_t from_us( uint64_t );
+__cfa_time_t from_ns( uint64_t );
+
+extern __cfa_time_t zero_time;
 
 //=============================================================================================
 // Clock logic
 //=============================================================================================
-
-#define TIMEGRAN 1_000_000_000L                         // nanosecond granularity, except for timeval
 
 __cfa_time_t __kernel_get_time();
@@ -57 +107 @@
 typedef alarm_node_t ** __alarm_it_t;
 
-void ?{}( alarm_node_t * this, thread_desc * thrd, __cfa_time_t alarm = 0, __cfa_time_t period = 0 );
-void ?{}( alarm_node_t * this, processor   * proc, __cfa_time_t alarm = 0, __cfa_time_t period = 0 );
+void ?{}( alarm_node_t * this, thread_desc * thrd, __cfa_time_t alarm = zero_time, __cfa_time_t period = zero_time );
+void ?{}( alarm_node_t * this, processor   * proc, __cfa_time_t alarm = zero_time, __cfa_time_t period = zero_time );
 void ^?{}( alarm_node_t * this );
 

src/libcfa/concurrency/coroutine

@@ -63 +63 @@
 
 // Get current coroutine
-extern volatile thread_local coroutine_desc * this_coroutine;
+extern thread_local coroutine_desc * volatile this_coroutine;
 
 // Private wrappers for context switch and stack creation

src/libcfa/concurrency/coroutine.c

@@ -26 +26 @@
 }
 
-#include "kernel"
-#include "libhdr.h"
+#include "kernel_private.h"
 
 #define __CFA_INVOKE_PRIVATE__
 #include "invoke.h"
 
-extern volatile thread_local processor * this_processor;
 
 //-----------------------------------------------------------------------------

src/libcfa/concurrency/kernel

@@ -28 +28 @@
 //-----------------------------------------------------------------------------
 // Locks
-bool try_lock  ( spinlock * DEBUG_CTX_PARAM2 );
-void lock      ( spinlock * DEBUG_CTX_PARAM2 );
-void lock_yield( spinlock * DEBUG_CTX_PARAM2 );
-void unlock    ( spinlock * );
+void lock      ( spinlock * DEBUG_CTX_PARAM2 );       // Lock the spinlock, spin if already acquired
+void lock_yield( spinlock * DEBUG_CTX_PARAM2 );       // Lock the spinlock, yield repeatedly if already acquired
+bool try_lock  ( spinlock * DEBUG_CTX_PARAM2 );       // Lock the spinlock, return false if already acquired
+void unlock    ( spinlock * );                        // Unlock the spinlock
 
 struct semaphore {
@@ -48 +48 @@
 // Cluster
 struct cluster {
-        __thread_queue_t ready_queue;
-        spinlock lock;
+        spinlock ready_queue_lock;                      // Ready queue locks
+        __thread_queue_t ready_queue;                   // Ready queue for threads
+        unsigned long long int preemption;              // Preemption rate on this cluster
 };
 
@@ -76 +77 @@
 static inline void ^?{}(FinishAction * this) {}
 
+// Processor
+// Wrapper around kernel threads
 struct processor {
-        struct processorCtx_t * runner;
-        cluster * cltr;
-        pthread_t kernel_thread;
+        // Main state
+        struct processorCtx_t * runner;                 // Coroutine ctx who does keeps the state of the processor
+        cluster * cltr;                                 // Cluster from which to get threads
+        pthread_t kernel_thread;                        // Handle to pthreads
 
-        semaphore terminated;
-        volatile bool is_terminated;
+        // Termination
+        volatile bool do_terminate;                     // Set to true to notify the processor should terminate
+        semaphore terminated;                           // Termination synchronisation
 
-        struct FinishAction finish;
+        // RunThread data
+        struct FinishAction finish;                     // Action to do after a thread is ran
 
-        struct alarm_node_t * preemption_alarm;
-        unsigned int preemption;
+        // Preemption data
+        struct alarm_node_t * preemption_alarm;         // Node which is added in the discrete event simulaiton
+        bool pending_preemption;                        // If true, a preemption was triggered in an unsafe region, the processor must preempt as soon as possible
 
-        bool pending_preemption;
-
-        char * last_enable;
+#ifdef __CFA_DEBUG__
+        char * last_enable;                             // Last function to enable preemption on this processor
+#endif
 };
 

src/libcfa/concurrency/kernel.c

@@ -42 +42 @@
 //-----------------------------------------------------------------------------
 // Kernel storage
-#define KERNEL_STORAGE(T,X) static char X##Storage[sizeof(T)]
-
-KERNEL_STORAGE(processorCtx_t, systemProcessorCtx);
-KERNEL_STORAGE(cluster, systemCluster);
-KERNEL_STORAGE(system_proc_t, systemProcessor);
-KERNEL_STORAGE(thread_desc, mainThread);
+KERNEL_STORAGE(cluster,           mainCluster);
+KERNEL_STORAGE(processor,         mainProcessor);
+KERNEL_STORAGE(processorCtx_t,    mainProcessorCtx);
+KERNEL_STORAGE(thread_desc,       mainThread);
 KERNEL_STORAGE(machine_context_t, mainThreadCtx);
 
-cluster * systemCluster;
-system_proc_t * systemProcessor;
+cluster *     mainCluster;
+processor *   mainProcessor;
 thread_desc * mainThread;
 
@@ -57 +55 @@
 // Global state
 
-volatile thread_local processor * this_processor;
-volatile thread_local coroutine_desc * this_coroutine;
-volatile thread_local thread_desc * this_thread;
+thread_local coroutine_desc * volatile this_coroutine;
+thread_local thread_desc *    volatile this_thread;
+thread_local processor *      volatile this_processor;
+
 volatile thread_local bool preemption_in_progress = 0;
 volatile thread_local unsigned short disable_preempt_count = 1;
@@ -85 +84 @@
 
         this->limit = (void *)(((intptr_t)this->base) - this->size);
-        this->context = &mainThreadCtxStorage;
+        this->context = &storage_mainThreadCtx;
         this->top = this->base;
 }
@@ -125 +124 @@
 
 void ?{}(processor * this) {
-        this{ systemCluster };
+        this{ mainCluster };
 }
 
@@ -131 +130 @@
         this->cltr = cltr;
         (&this->terminated){ 0 };
-        this->is_terminated = false;
+        this->do_terminate = false;
         this->preemption_alarm = NULL;
-        this->preemption = default_preemption();
         this->pending_preemption = false;
 
@@ -142 +140 @@
         this->cltr = cltr;
         (&this->terminated){ 0 };
-        this->is_terminated = false;
+        this->do_terminate = false;
         this->preemption_alarm = NULL;
-        this->preemption = default_preemption();
         this->pending_preemption = false;
         this->kernel_thread = pthread_self();
 
         this->runner = runner;
-        LIB_DEBUG_PRINT_SAFE("Kernel : constructing system processor context %p\n", runner);
+        LIB_DEBUG_PRINT_SAFE("Kernel : constructing main processor context %p\n", runner);
         runner{ this };
 }
 
-LIB_DEBUG_DO( bool validate( alarm_list_t * this ); )
-
-void ?{}(system_proc_t * this, cluster * cltr, processorCtx_t * runner) {
-        (&this->alarms){};
-        (&this->alarm_lock){};
-        this->pending_alarm = false;
-
-        (&this->proc){ cltr, runner };
-
-        verify( validate( &this->alarms ) );
-}
-
 void ^?{}(processor * this) {
-        if( ! this->is_terminated ) {
+        if( ! this->do_terminate ) {
                 LIB_DEBUG_PRINT_SAFE("Kernel : core %p signaling termination\n", this);
-                this->is_terminated = true;
+                this->do_terminate = true;
                 P( &this->terminated );
                 pthread_join( this->kernel_thread, NULL );
@@ -176 +161 @@
 void ?{}(cluster * this) {
         ( &this->ready_queue ){};
-        ( &this->lock ){};
+        ( &this->ready_queue_lock ){};
+
+        this->preemption = default_preemption();
 }
 
@@ -199 +186 @@
 
                 thread_desc * readyThread = NULL;
-                for( unsigned int spin_count = 0; ! this->is_terminated; spin_count++ )
+                for( unsigned int spin_count = 0; ! this->do_terminate; spin_count++ )
                 {
                         readyThread = nextThread( this->cltr );
@@ -343 +330 @@
         verifyf( thrd->next == NULL, "Expected null got %p", thrd->next );
 
-        lock( &systemProcessor->proc.cltr->lock DEBUG_CTX2 );
-        append( &systemProcessor->proc.cltr->ready_queue, thrd );
-        unlock( &systemProcessor->proc.cltr->lock );
+        lock(   &this_processor->cltr->ready_queue_lock DEBUG_CTX2 );
+        append( &this_processor->cltr->ready_queue, thrd );
+        unlock( &this_processor->cltr->ready_queue_lock );
 
         verify( disable_preempt_count > 0 );
@@ -352 +339 @@
 thread_desc * nextThread(cluster * this) {
         verify( disable_preempt_count > 0 );
-        lock( &this->lock DEBUG_CTX2 );
+        lock( &this->ready_queue_lock DEBUG_CTX2 );
         thread_desc * head = pop_head( &this->ready_queue );
-        unlock( &this->lock );
+        unlock( &this->ready_queue_lock );
         verify( disable_preempt_count > 0 );
         return head;
@@ -452 +439 @@
         // Start by initializing the main thread
         // SKULLDUGGERY: the mainThread steals the process main thread
-        // which will then be scheduled by the systemProcessor normally
-        mainThread = (thread_desc *)&mainThreadStorage;
+        // which will then be scheduled by the mainProcessor normally
+        mainThread = (thread_desc *)&storage_mainThread;
         current_stack_info_t info;
         mainThread{ &info };
@@ -459 +446 @@
         LIB_DEBUG_PRINT_SAFE("Kernel : Main thread ready\n");
 
-        // Initialize the system cluster
-        systemCluster = (cluster *)&systemClusterStorage;
-        systemCluster{};
-
-        LIB_DEBUG_PRINT_SAFE("Kernel : System cluster ready\n");
-
-        // Initialize the system processor and the system processor ctx
+        // Initialize the main cluster
+        mainCluster = (cluster *)&storage_mainCluster;
+        mainCluster{};
+
+        LIB_DEBUG_PRINT_SAFE("Kernel : main cluster ready\n");
+
+        // Initialize the main processor and the main processor ctx
         // (the coroutine that contains the processing control flow)
-        systemProcessor = (system_proc_t *)&systemProcessorStorage;
-        systemProcessor{ systemCluster, (processorCtx_t *)&systemProcessorCtxStorage };
-
-        // Add the main thread to the ready queue
-        // once resume is called on systemProcessor->runner the mainThread needs to be scheduled like any normal thread
-        ScheduleThread(mainThread);
+        mainProcessor = (processor *)&storage_mainProcessor;
+        mainProcessor{ mainCluster, (processorCtx_t *)&storage_mainProcessorCtx };
 
         //initialize the global state variables
-        this_processor = &systemProcessor->proc;
+        this_processor = mainProcessor;
         this_thread = mainThread;
         this_coroutine = &mainThread->cor;
-        disable_preempt_count = 1;
 
         // Enable preemption
         kernel_start_preemption();
 
-        // SKULLDUGGERY: Force a context switch to the system processor to set the main thread's context to the current UNIX
+        // Add the main thread to the ready queue
+        // once resume is called on mainProcessor->runner the mainThread needs to be scheduled like any normal thread
+        ScheduleThread(mainThread);
+
+        // SKULLDUGGERY: Force a context switch to the main processor to set the main thread's context to the current UNIX
         // context. Hence, the main thread does not begin through CtxInvokeThread, like all other threads. The trick here is that
         // mainThread is on the ready queue when this call is made.
-        resume( systemProcessor->proc.runner );
+        resume( mainProcessor->runner );
 
 
@@ -501 +487 @@
         disable_interrupts();
 
-        // SKULLDUGGERY: Notify the systemProcessor it needs to terminates.
+        // SKULLDUGGERY: Notify the mainProcessor it needs to terminates.
         // When its coroutine terminates, it return control to the mainThread
         // which is currently here
-        systemProcessor->proc.is_terminated = true;
+        mainProcessor->do_terminate = true;
         suspend();
 
@@ -512 +498 @@
         kernel_stop_preemption();
 
-        // Destroy the system processor and its context in reverse order of construction
+        // Destroy the main processor and its context in reverse order of construction
         // These were manually constructed so we need manually destroy them
-        ^(systemProcessor->proc.runner){};
-        ^(systemProcessor){};
+        ^(mainProcessor->runner){};
+        ^(mainProcessor){};
 
         // Final step, destroy the main thread since it is no longer needed

src/libcfa/concurrency/kernel_private.h

@@ -31 +31 @@
 extern "C" {
         void disable_interrupts();
-        void enable_interrupts_noRF();
+        void enable_interrupts_noPoll();
         void enable_interrupts( DEBUG_CTX_PARAM );
 }
@@ -45 +45 @@
 thread_desc * nextThread(cluster * this);
 
+//Block current thread and release/wake-up the following resources
 void BlockInternal(void);
 void BlockInternal(spinlock * lock);
@@ -65 +66 @@
 void spin(processor * this, unsigned int * spin_count);
 
-struct system_proc_t {
-        processor proc;
-
+struct event_kernel_t {
         alarm_list_t alarms;
-        spinlock alarm_lock;
-
-        bool pending_alarm;
+        spinlock lock;
 };
 
-extern cluster * systemCluster;
-extern system_proc_t * systemProcessor;
-extern volatile thread_local processor * this_processor;
-extern volatile thread_local coroutine_desc * this_coroutine;
-extern volatile thread_local thread_desc * this_thread;
+extern event_kernel_t * event_kernel;
+
+extern thread_local coroutine_desc * volatile this_coroutine;
+extern thread_local thread_desc *    volatile this_thread;
+extern thread_local processor *      volatile this_processor;
+
 extern volatile thread_local bool preemption_in_progress;
 extern volatile thread_local unsigned short disable_preempt_count;
@@ -91 +89 @@
 extern void ThreadCtxSwitch(coroutine_desc * src, coroutine_desc * dst);
 
+//-----------------------------------------------------------------------------
+// Utils
+#define KERNEL_STORAGE(T,X) static char storage_##X[sizeof(T)]
+
 #endif //KERNEL_PRIVATE_H
 

src/libcfa/concurrency/preemption.c

@@ -34 +34 @@
 #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_alarm    ( __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 );
-LIB_DEBUG_DO( bool validate( alarm_list_t * this ); )
-
+
+// FwdDeclarations : alarm thread main
+void * alarm_loop( __attribute__((unused)) void * args );
+
+// Machine specific register name
 #ifdef __x86_64__
 #define CFA_REG_IP REG_RIP
@@ -60 +68 @@
 #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){};
+}
 
 //=============================================================================================
@@ -65 +81 @@
 //=============================================================================================
 
+// 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();
-
-        // LIB_DEBUG_PRINT_BUFFER_DECL( STDERR_FILENO, "Ticking preemption @ %llu\n", currtime );
-        while( alarms->head && alarms->head->alarm < currtime ) {
-                alarm_node_t * node = pop(alarms);
-                // LIB_DEBUG_PRINT_BUFFER_LOCAL( STDERR_FILENO, "Ticking %p\n", node );
-
+        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 );
@@ -81 +105 @@
                 }
 
-                verify( validate( alarms ) );
-
+                // Check if this is a periodic alarm
                 __cfa_time_t period = node->period;
                 if( period > 0 ) {
-                        node->alarm = currtime + period;
-                        // LIB_DEBUG_PRINT_BUFFER_LOCAL( STDERR_FILENO, "Reinsert %p @ %llu (%llu + %llu)\n", node, node->alarm, currtime, period );
-                        insert( alarms, node );
+                        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 );
-        }
-
-        verify( validate( alarms ) );
-        // LIB_DEBUG_PRINT_BUFFER_LOCAL( STDERR_FILENO, "Ticking preemption done\n" );
-}
-
+                        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 ) {
-        LIB_DEBUG_PRINT_BUFFER_DECL( STDERR_FILENO, "Processor : %p updating preemption to %llu\n", this, duration );
-
         alarm_node_t * alarm = this->preemption_alarm;
-        duration *= 1000;
 
         // Alarms need to be enabled
@@ -136 +152 @@
 
 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 < (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 );
-        }
-
+                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;
-                thread_desc * thrd = this_thread;
+                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 != (unsigned short) 0 );
+                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;
@@ -157 +173 @@
                 }
 
+                // 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;
@@ -171 +196 @@
 }
 
+// sigprocmask wrapper : block a single signal
 static inline void signal_block( int sig ) {
         sigset_t mask;
@@ -181 +207 @@
 }
 
-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;
-}
-
+// 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
 //=============================================================================================
 
-static pthread_t alarm_thread;
-void * alarm_loop( __attribute__((unused)) void * args );
-
+// Startup routine to activate preemption
+// Called from kernel_startup
 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 );
+
+        // 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 );
@@ -219 +253 @@
 }
 
+// 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) );
 }
 
@@ -242 +288 @@
         disable_interrupts();
 
-        update_preemption( this->proc, 0 );
+        update_preemption( this->proc, zero_time );
 }
 
@@ -249 +295 @@
 //=============================================================================================
 
+// 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]); )
-        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();
-        }
-}
-
+
+        // 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 );
@@ -272 +324 @@
         }
 
+        // 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( &systemProcessor->alarm_lock DEBUG_CTX2 );
+                        lock( &event_kernel->lock DEBUG_CTX2 );
                         tick_preemption();
-                        unlock( &systemProcessor->alarm_lock );
+                        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;
                 }
@@ -297 +359 @@
 }
 
+// Sigaction wrapper : register an signal handler
 static void __kernel_sigaction( int sig, void (*handler)(__CFA_SIGPARMS__), int flags ) {
         struct sigaction act;
@@ -312 +375 @@
 }
 
-typedef void (*sa_handler_t)(int);
-
+// Sigaction wrapper : restore default handler
 static void __kernel_sigdefault( int sig ) {
         struct sigaction act;
 
-        // act.sa_handler = SIG_DFL;
+        act.sa_handler = SIG_DFL;
         act.sa_flags = 0;
         sigemptyset( &act.sa_mask );

src/libcfa/concurrency/thread

@@ -54 +54 @@
 }
 
-extern volatile thread_local thread_desc * this_thread;
+extern thread_local thread_desc * volatile this_thread;
 
 forall( dtype T | is_thread(T) )

src/libcfa/concurrency/thread.c

@@ -87 +87 @@
 
 void yield( void ) {
-        BlockInternal( (thread_desc *)this_thread );
+        BlockInternal( this_thread );
 }