source: libcfa/src/concurrency/preemption.cfa @ 8fc652e0

arm-ehjacob/cs343-translationnew-ast-unique-expr
Last change on this file since 8fc652e0 was 8fc652e0, checked in by Thierry Delisle <tdelisle@…>, 15 months ago

Change usage of TLS to more strongly segregate in kernel and out of kernel usage.

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File size: 22.3 KB
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1//
2// Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
3//
4// The contents of this file are covered under the licence agreement in the
5// file "LICENCE" distributed with Cforall.
6//
7// signal.c --
8//
9// Author           : Thierry Delisle
10// Created On       : Mon Jun 5 14:20:42 2017
11// Last Modified By : Peter A. Buhr
12// Last Modified On : Wed Aug 26 16:46:03 2020
13// Update Count     : 53
14//
15
16#define __cforall_thread__
17
18#include "preemption.hfa"
19#include <assert.h>
20
21#include <errno.h>
22#include <stdio.h>
23#include <string.h>
24#include <unistd.h>
25#include <limits.h>                                                                             // PTHREAD_STACK_MIN
26
27#include "bits/signal.hfa"
28#include "kernel_private.hfa"
29
30#if !defined(__CFA_DEFAULT_PREEMPTION__)
31#define __CFA_DEFAULT_PREEMPTION__ 10`ms
32#endif
33
34Duration default_preemption() __attribute__((weak)) {
35        return __CFA_DEFAULT_PREEMPTION__;
36}
37
38// FwdDeclarations : timeout handlers
39static void preempt( processor   * this );
40static void timeout( $thread * this );
41
42// FwdDeclarations : Signal handlers
43static void sigHandler_ctxSwitch( __CFA_SIGPARMS__ );
44static void sigHandler_alarm    ( __CFA_SIGPARMS__ );
45static void sigHandler_segv     ( __CFA_SIGPARMS__ );
46static void sigHandler_ill      ( __CFA_SIGPARMS__ );
47static void sigHandler_fpe      ( __CFA_SIGPARMS__ );
48static void sigHandler_abort    ( __CFA_SIGPARMS__ );
49
50// FwdDeclarations : alarm thread main
51static void * alarm_loop( __attribute__((unused)) void * args );
52
53// Machine specific register name
54#if   defined( __i386 )
55#define CFA_REG_IP gregs[REG_EIP]
56#elif defined( __x86_64 )
57#define CFA_REG_IP gregs[REG_RIP]
58#elif defined( __arm__ )
59#define CFA_REG_IP arm_pc
60#elif defined( __aarch64__ )
61#define CFA_REG_IP pc
62#else
63#error unsupported hardware architecture
64#endif
65
66KERNEL_STORAGE(event_kernel_t, event_kernel);         // private storage for event kernel
67event_kernel_t * event_kernel;                        // kernel public handle to even kernel
68static pthread_t alarm_thread;                        // pthread handle to alarm thread
69static void * alarm_stack;                                                        // pthread stack for alarm thread
70
71static void ?{}(event_kernel_t & this) with( this ) {
72        alarms{};
73        lock{};
74}
75
76enum {
77        PREEMPT_NORMAL    = 0,
78        PREEMPT_TERMINATE = 1,
79};
80
81//=============================================================================================
82// Kernel Preemption logic
83//=============================================================================================
84
85// Get next expired node
86static inline alarm_node_t * get_expired( alarm_list_t * alarms, Time currtime ) {
87        if( ! & (*alarms)`first ) return 0p;                                            // If no alarms return null
88        if( (*alarms)`first.alarm >= currtime ) return 0p;      // If alarms head not expired return null
89        return pop(alarms);                                                                     // Otherwise just pop head
90}
91
92// Tick one frame of the Discrete Event Simulation for alarms
93static void tick_preemption(void) {
94        alarm_node_t * node = 0p;                                                       // Used in the while loop but cannot be declared in the while condition
95        alarm_list_t * alarms = &event_kernel->alarms;          // Local copy for ease of reading
96        Time currtime = __kernel_get_time();                            // Check current time once so everything "happens at once"
97
98        //Loop throught every thing expired
99        while( node = get_expired( alarms, currtime ) ) {
100                // __cfaabi_dbg_print_buffer_decl( " KERNEL: preemption tick.\n" );
101                Duration period = node->period;
102                if( period == 0) {
103                        node->set = false;                  // Node is one-shot, just mark it as not pending
104                }
105
106                // Check if this is a kernel
107                if( node->type == Kernel ) {
108                        preempt( node->proc );
109                }
110                else if( node->type == User ) {
111                        timeout( node->thrd );
112                }
113                else {
114                        node->callback(*node);
115                }
116
117                // Check if this is a periodic alarm
118                if( period > 0 ) {
119                        // __cfaabi_dbg_print_buffer_local( " KERNEL: alarm period is %lu.\n", period.tv );
120                        node->alarm = currtime + period;    // Alarm is periodic, add currtime to it (used cached current time)
121                        insert( alarms, node );             // Reinsert the node for the next time it triggers
122                }
123        }
124
125        // If there are still alarms pending, reset the timer
126        if( & (*alarms)`first ) {
127                __cfadbg_print_buffer_decl(preemption, " KERNEL: @%ju(%ju) resetting alarm to %ju.\n", currtime.tv, __kernel_get_time().tv, (alarms->head->alarm - currtime).tv);
128                Duration delta = (*alarms)`first.alarm - currtime;
129                Duration capped = max(delta, 50`us);
130                // itimerval tim  = { caped };
131                // __cfaabi_dbg_print_buffer_local( "    Values are %lu, %lu, %lu %lu.\n", delta.tv, caped.tv, tim.it_value.tv_sec, tim.it_value.tv_usec);
132
133                __kernel_set_timer( capped );
134        }
135}
136
137// Update the preemption of a processor and notify interested parties
138void update_preemption( processor * this, Duration duration ) {
139        alarm_node_t * alarm = this->preemption_alarm;
140
141        // Alarms need to be enabled
142        if ( duration > 0 && ! alarm->set ) {
143                alarm->alarm = __kernel_get_time() + duration;
144                alarm->period = duration;
145                register_self( alarm );
146        }
147        // Zero duration but alarm is set
148        else if ( duration == 0 && alarm->set ) {
149                unregister_self( alarm );
150                alarm->alarm = 0;
151                alarm->period = 0;
152        }
153        // If alarm is different from previous, change it
154        else if ( duration > 0 && alarm->period != duration ) {
155                unregister_self( alarm );
156                alarm->alarm = __kernel_get_time() + duration;
157                alarm->period = duration;
158                register_self( alarm );
159        }
160}
161
162//=============================================================================================
163// Kernel Signal Tools
164//=============================================================================================
165
166//----------
167// special case for preemption since used often
168bool __preemption_enabled() {
169        // create a assembler label before
170        // marked as clobber all to avoid movement
171        asm volatile("__cfaasm_check_before:":::"memory");
172
173        // access tls as normal
174        bool enabled = __cfaabi_tls.preemption_state.enabled;
175
176        // create a assembler label after
177        // marked as clobber all to avoid movement
178        asm volatile("__cfaasm_check_after:":::"memory");
179        return enabled;
180}
181
182//----------
183// Get data from the TLS block
184uintptr_t __cfatls_get( unsigned long int offset ) __attribute__((__noinline__)); //no inline to avoid problems
185uintptr_t __cfatls_get( unsigned long int offset ) {
186        // create a assembler label before
187        // marked as clobber all to avoid movement
188        asm volatile("__cfaasm_get_before:":::"memory");
189
190        // access tls as normal (except for pointer arithmetic)
191        uintptr_t val = *(uintptr_t*)((uintptr_t)&__cfaabi_tls + offset);
192
193        // create a assembler label after
194        // marked as clobber all to avoid movement
195        asm volatile("__cfaasm_get_after:":::"memory");
196        return val;
197}
198
199// //----------
200// // Write data to the TLS block
201// // sadly it looses the type information and can only write 1 word at a time
202// // use with __builtin_offsetof
203// void __cfatls_set(uintptr_t offset, void * value) __attribute__((__noinline__));
204// void __cfatls_set(uintptr_t offset, void * value) {
205//     // create a assembler label before
206//     // marked as clobber all to avoid movement
207//     asm volatile("__cfaasm_set_before:":::"memory");
208
209//     // access tls as normal (except for type information)
210//     *(void**)(offset + (uintptr_t)&my_tls) = value;
211
212//     // create a assembler label after
213//     // marked as clobber all to avoid movement
214//     asm volatile("__cfaasm_set_after:":::"memory");
215// }
216
217// //----------
218// #include <stdio.h>
219// int main() {
220//     // Get the information
221//     // Must use inline assembly to get access to label
222//     // C is annoying here because this could easily be a static const but "initializer element is not a compile-time constant"
223//     // The big advantage of this approach is that there is 0 overhead for the read and writes function
224//     void * __cfaasm_addr_get_before = ({ void * value; asm("movq $__cfaasm_get_before, %[v]\n\t" : [v]"=r"(value) ); value; });
225//     void * __cfaasm_addr_get_after  = ({ void * value; asm("movq $__cfaasm_get_after , %[v]\n\t" : [v]"=r"(value) ); value; });
226//     void * __cfaasm_addr_set_before = ({ void * value; asm("movq $__cfaasm_set_before, %[v]\n\t" : [v]"=r"(value) ); value; });
227//     void * __cfaasm_addr_set_after  = ({ void * value; asm("movq $__cfaasm_set_after , %[v]\n\t" : [v]"=r"(value) ); value; });
228
229//     printf("%p to %p\n", __cfaasm_addr_get_before, __cfaasm_addr_get_after);
230//     printf("%p to %p\n", __cfaasm_addr_set_before, __cfaasm_addr_set_after);
231//     return 0;
232// }
233
234__cfaabi_dbg_debug_do( static thread_local void * last_interrupt = 0; )
235
236extern "C" {
237        // Disable interrupts by incrementing the counter
238        void disable_interrupts() {
239                // create a assembler label before
240                // marked as clobber all to avoid movement
241                asm volatile("__cfaasm_disable_before:":::"memory");
242
243                with( __cfaabi_tls.preemption_state ) {
244                        #if GCC_VERSION > 50000
245                        static_assert(__atomic_always_lock_free(sizeof(enabled), &enabled), "Must be lock-free");
246                        #endif
247
248                        // Set enabled flag to false
249                        // should be atomic to avoid preemption in the middle of the operation.
250                        // use memory order RELAXED since there is no inter-thread on this variable requirements
251                        __atomic_store_n(&enabled, false, __ATOMIC_RELAXED);
252
253                        // Signal the compiler that a fence is needed but only for signal handlers
254                        __atomic_signal_fence(__ATOMIC_ACQUIRE);
255
256                        __attribute__((unused)) unsigned short new_val = disable_count + 1;
257                        disable_count = new_val;
258                        verify( new_val < 65_000u );              // If this triggers someone is disabling interrupts without enabling them
259                }
260
261                // create a assembler label after
262                // marked as clobber all to avoid movement
263                asm volatile("__cfaasm_disable_after:":::"memory");
264        }
265
266        // Enable interrupts by decrementing the counter
267        // If counter reaches 0, execute any pending __cfactx_switch
268        void enable_interrupts( __cfaabi_dbg_ctx_param ) {
269                // create a assembler label before
270                // marked as clobber all to avoid movement
271                asm volatile("__cfaasm_enable_before:":::"memory");
272
273                processor   * proc = __cfaabi_tls.this_processor; // Cache the processor now since interrupts can start happening after the atomic store
274                /* paranoid */ verify( proc );
275
276                with( __cfaabi_tls.preemption_state ){
277                        unsigned short prev = disable_count;
278                        disable_count -= 1;
279                        verify( prev != 0u );                     // If this triggers someone is enabled already enabled interruptsverify( prev != 0u );
280
281                        // Check if we need to prempt the thread because an interrupt was missed
282                        if( prev == 1 ) {
283                                #if GCC_VERSION > 50000
284                                static_assert(__atomic_always_lock_free(sizeof(enabled), &enabled), "Must be lock-free");
285                                #endif
286
287                                // Set enabled flag to true
288                                // should be atomic to avoid preemption in the middle of the operation.
289                                // use memory order RELAXED since there is no inter-thread on this variable requirements
290                                __atomic_store_n(&enabled, true, __ATOMIC_RELAXED);
291
292                                // Signal the compiler that a fence is needed but only for signal handlers
293                                __atomic_signal_fence(__ATOMIC_RELEASE);
294                                if( proc->pending_preemption ) {
295                                        proc->pending_preemption = false;
296                                        force_yield( __POLL_PREEMPTION );
297                                }
298                        }
299                }
300
301                // For debugging purposes : keep track of the last person to enable the interrupts
302                __cfaabi_dbg_debug_do( proc->last_enable = caller; )
303
304                // create a assembler label after
305                // marked as clobber all to avoid movement
306                asm volatile("__cfaasm_enable_after:":::"memory");
307        }
308
309        // Disable interrupts by incrementint the counter
310        // Don't execute any pending __cfactx_switch even if counter reaches 0
311        void enable_interrupts_noPoll() {
312                // create a assembler label before
313                // marked as clobber all to avoid movement
314                asm volatile("__cfaasm_nopoll_before:":::"memory");
315
316                unsigned short prev = __cfaabi_tls.preemption_state.disable_count;
317                __cfaabi_tls.preemption_state.disable_count -= 1;
318                verifyf( prev != 0u, "Incremented from %u\n", prev );                     // If this triggers someone is enabled already enabled interrupts
319                if( prev == 1 ) {
320                        #if GCC_VERSION > 50000
321                        static_assert(__atomic_always_lock_free(sizeof(__cfaabi_tls.preemption_state.enabled), &__cfaabi_tls.preemption_state.enabled), "Must be lock-free");
322                        #endif
323                        // Set enabled flag to true
324                        // should be atomic to avoid preemption in the middle of the operation.
325                        // use memory order RELAXED since there is no inter-thread on this variable requirements
326                        __atomic_store_n(&__cfaabi_tls.preemption_state.enabled, true, __ATOMIC_RELAXED);
327
328                        // Signal the compiler that a fence is needed but only for signal handlers
329                        __atomic_signal_fence(__ATOMIC_RELEASE);
330                }
331
332                // create a assembler label after
333                // marked as clobber all to avoid movement
334                asm volatile("__cfaasm_nopoll_after:":::"memory");
335        }
336}
337
338// sigprocmask wrapper : unblock a single signal
339static inline void signal_unblock( int sig ) {
340        sigset_t mask;
341        sigemptyset( &mask );
342        sigaddset( &mask, sig );
343
344        if ( pthread_sigmask( SIG_UNBLOCK, &mask, 0p ) == -1 ) {
345            abort( "internal error, pthread_sigmask" );
346        }
347}
348
349// sigprocmask wrapper : block a single signal
350static inline void signal_block( int sig ) {
351        sigset_t mask;
352        sigemptyset( &mask );
353        sigaddset( &mask, sig );
354
355        if ( pthread_sigmask( SIG_BLOCK, &mask, 0p ) == -1 ) {
356                abort( "internal error, pthread_sigmask" );
357        }
358}
359
360// kill wrapper : signal a processor
361static void preempt( processor * this ) {
362        sigval_t value = { PREEMPT_NORMAL };
363        pthread_sigqueue( this->kernel_thread, SIGUSR1, value );
364}
365
366// reserved for future use
367static void timeout( $thread * this ) {
368        #if !defined( __CFA_NO_STATISTICS__ )
369                kernelTLS().this_stats = this->curr_cluster->stats;
370        #endif
371        unpark( this );
372}
373
374// KERNEL ONLY
375// Check if a __cfactx_switch signal handler shoud defer
376// If true  : preemption is safe
377// If false : preemption is unsafe and marked as pending
378static inline bool preemption_ready() {
379        // Check if preemption is safe
380        bool ready = __cfaabi_tls.preemption_state.enabled && ! __cfaabi_tls.preemption_state.in_progress;
381
382        // Adjust the pending flag accordingly
383        __cfaabi_tls.this_processor->pending_preemption = !ready;
384        return ready;
385}
386
387//=============================================================================================
388// Kernel Signal Startup/Shutdown logic
389//=============================================================================================
390
391// Startup routine to activate preemption
392// Called from kernel_startup
393void __kernel_alarm_startup() {
394        __cfaabi_dbg_print_safe( "Kernel : Starting preemption\n" );
395
396        // Start with preemption disabled until ready
397        __cfaabi_tls.preemption_state.enabled = false;
398        __cfaabi_tls.preemption_state.disable_count = 1;
399
400        // Initialize the event kernel
401        event_kernel = (event_kernel_t *)&storage_event_kernel;
402        (*event_kernel){};
403
404        // Setup proper signal handlers
405        __cfaabi_sigaction( SIGUSR1, sigHandler_ctxSwitch, SA_SIGINFO | SA_RESTART ); // __cfactx_switch handler
406        __cfaabi_sigaction( SIGALRM, sigHandler_alarm    , SA_SIGINFO | SA_RESTART ); // debug handler
407
408        signal_block( SIGALRM );
409
410        alarm_stack = __create_pthread( &alarm_thread, alarm_loop, 0p );
411}
412
413// Shutdown routine to deactivate preemption
414// Called from kernel_shutdown
415void __kernel_alarm_shutdown() {
416        __cfaabi_dbg_print_safe( "Kernel : Preemption stopping\n" );
417
418        // Block all signals since we are already shutting down
419        sigset_t mask;
420        sigfillset( &mask );
421        sigprocmask( SIG_BLOCK, &mask, 0p );
422
423        // Notify the alarm thread of the shutdown
424        sigval val = { 1 };
425        pthread_sigqueue( alarm_thread, SIGALRM, val );
426
427        // Wait for the preemption thread to finish
428
429        pthread_join( alarm_thread, 0p );
430        free( alarm_stack );
431
432        // Preemption is now fully stopped
433
434        __cfaabi_dbg_print_safe( "Kernel : Preemption stopped\n" );
435}
436
437// Raii ctor/dtor for the preemption_scope
438// Used by thread to control when they want to receive preemption signals
439void ?{}( preemption_scope & this, processor * proc ) {
440        (this.alarm){ proc, (Time){ 0 }, 0`s };
441        this.proc = proc;
442        this.proc->preemption_alarm = &this.alarm;
443
444        update_preemption( this.proc, this.proc->cltr->preemption_rate );
445}
446
447void ^?{}( preemption_scope & this ) {
448        disable_interrupts();
449
450        update_preemption( this.proc, 0`s );
451}
452
453//=============================================================================================
454// Kernel Signal Handlers
455//=============================================================================================
456struct asm_region {
457        void * before;
458        void * after;
459};
460
461//-----------------------------------------------------------------------------
462// Some assembly required
463#if defined( __i386 )
464        #define __cfaasm_label( label ) \
465                ({ \
466                        struct asm_region region; \
467                        asm( \
468                                "movl $__cfaasm_" #label "_before, %[vb]\n\t" \
469                                "movl $__cfaasm_" #label "_after , %[va]\n\t" \
470                                 : [vb]"=r"(region.before), [vb]"=r"(region.before) \
471                        ); \
472                        region; \
473                });
474#elif defined( __x86_64 )
475        #ifdef __PIC__
476                #define PLT "@PLT"
477        #else
478                #define PLT ""
479        #endif
480        #define __cfaasm_label( label ) \
481                ({ \
482                        struct asm_region region; \
483                        asm( \
484                                "movq $__cfaasm_" #label "_before" PLT ", %[vb]\n\t" \
485                                "movq $__cfaasm_" #label "_after"  PLT ", %[va]\n\t" \
486                                 : [vb]"=r"(region.before), [va]"=r"(region.after) \
487                        ); \
488                        region; \
489                });
490#elif defined( __aarch64__ )
491        #error __cfaasm_label undefined for arm
492#else
493        #error unknown hardware architecture
494#endif
495
496// Context switch signal handler
497// Receives SIGUSR1 signal and causes the current thread to yield
498static void sigHandler_ctxSwitch( __CFA_SIGPARMS__ ) {
499        void * ip = (void *)(cxt->uc_mcontext.CFA_REG_IP);
500        __cfaabi_dbg_debug_do( last_interrupt = ip; )
501
502        // SKULLDUGGERY: if a thread creates a processor and the immediately deletes it,
503        // the interrupt that is supposed to force the kernel thread to preempt might arrive
504        // before the kernel thread has even started running. When that happens, an interrupt
505        // with a null 'this_processor' will be caught, just ignore it.
506        if(! __cfaabi_tls.this_processor ) return;
507
508        choose(sfp->si_value.sival_int) {
509                case PREEMPT_NORMAL   : ;// Normal case, nothing to do here
510                case PREEMPT_TERMINATE: verify( __atomic_load_n( &__cfaabi_tls.this_processor->do_terminate, __ATOMIC_SEQ_CST ) );
511                default:
512                        abort( "internal error, signal value is %d", sfp->si_value.sival_int );
513        }
514
515        // Check if it is safe to preempt here
516        if( !preemption_ready() ) { return; }
517
518        struct asm_region region;
519        region = __cfaasm_label( get     ); if( ip >= region.before && ip <= region.after ) return;
520        region = __cfaasm_label( check   ); if( ip >= region.before && ip <= region.after ) return;
521        region = __cfaasm_label( disable ); if( ip >= region.before && ip <= region.after ) return;
522        region = __cfaasm_label( enable  ); if( ip >= region.before && ip <= region.after ) return;
523        region = __cfaasm_label( nopoll  ); if( ip >= region.before && ip <= region.after ) return;
524
525        __cfaabi_dbg_print_buffer_decl( " KERNEL: preempting core %p (%p @ %p).\n", __cfaabi_tls.this_processor, __cfaabi_tls.this_thread, (void *)(cxt->uc_mcontext.CFA_REG_IP) );
526
527        // Sync flag : prevent recursive calls to the signal handler
528        __cfaabi_tls.preemption_state.in_progress = true;
529
530        // Clear sighandler mask before context switching.
531        #if GCC_VERSION > 50000
532        static_assert( sizeof( sigset_t ) == sizeof( cxt->uc_sigmask ), "Expected cxt->uc_sigmask to be of sigset_t" );
533        #endif
534        if ( pthread_sigmask( SIG_SETMASK, (sigset_t *)&(cxt->uc_sigmask), 0p ) == -1 ) {
535                abort( "internal error, sigprocmask" );
536        }
537
538        // Clear the in progress flag
539        __cfaabi_tls.preemption_state.in_progress = false;
540
541        // Preemption can occur here
542
543        force_yield( __ALARM_PREEMPTION ); // Do the actual __cfactx_switch
544}
545
546static void sigHandler_alarm( __CFA_SIGPARMS__ ) {
547        abort("SIGALRM should never reach the signal handler");
548}
549
550// Main of the alarm thread
551// Waits on SIGALRM and send SIGUSR1 to whom ever needs it
552static void * alarm_loop( __attribute__((unused)) void * args ) {
553        __processor_id_t id;
554        id.full_proc = false;
555        id.id = doregister(&id);
556        __cfaabi_tls.this_proc_id = &id;
557
558        // Block sigalrms to control when they arrive
559        sigset_t mask;
560        sigfillset(&mask);
561        if ( pthread_sigmask( SIG_BLOCK, &mask, 0p ) == -1 ) {
562            abort( "internal error, pthread_sigmask" );
563        }
564
565        sigemptyset( &mask );
566        sigaddset( &mask, SIGALRM );
567
568        // Main loop
569        while( true ) {
570                // Wait for a sigalrm
571                siginfo_t info;
572                int sig = sigwaitinfo( &mask, &info );
573
574                if( sig < 0 ) {
575                        //Error!
576                        int err = errno;
577                        switch( err ) {
578                                case EAGAIN :
579                                case EINTR :
580                                        {__cfaabi_dbg_print_buffer_decl( " KERNEL: Spurious wakeup %d.\n", err );}
581                                        continue;
582                                case EINVAL :
583                                        abort( "Timeout was invalid." );
584                                default:
585                                        abort( "Unhandled error %d", err);
586                        }
587                }
588
589                // If another signal arrived something went wrong
590                assertf(sig == SIGALRM, "Kernel Internal Error, sigwait: Unexpected signal %d (%d : %d)\n", sig, info.si_code, info.si_value.sival_int);
591
592                // __cfaabi_dbg_print_safe( "Kernel : Caught alarm from %d with %d\n", info.si_code, info.si_value.sival_int );
593                // Switch on the code (a.k.a. the sender) to
594                switch( info.si_code )
595                {
596                // Timers can apparently be marked as sent for the kernel
597                // In either case, tick preemption
598                case SI_TIMER:
599                case SI_KERNEL:
600                        // __cfaabi_dbg_print_safe( "Kernel : Preemption thread tick\n" );
601                        lock( event_kernel->lock __cfaabi_dbg_ctx2 );
602                        tick_preemption();
603                        unlock( event_kernel->lock );
604                        break;
605                // Signal was not sent by the kernel but by an other thread
606                case SI_QUEUE:
607                        // For now, other thread only signal the alarm thread to shut it down
608                        // If this needs to change use info.si_value and handle the case here
609                        goto EXIT;
610                }
611        }
612
613EXIT:
614        __cfaabi_dbg_print_safe( "Kernel : Preemption thread stopping\n" );
615        unregister(&id);
616        return 0p;
617}
618
619//=============================================================================================
620// Kernel Signal Debug
621//=============================================================================================
622
623void __cfaabi_check_preemption() {
624        bool ready = __preemption_enabled();
625        if(!ready) { abort("Preemption should be ready"); }
626
627        sigset_t oldset;
628        int ret;
629        ret = pthread_sigmask(0, ( const sigset_t * ) 0p, &oldset);  // workaround trac#208: cast should be unnecessary
630        if(ret != 0) { abort("ERROR sigprocmask returned %d", ret); }
631
632        ret = sigismember(&oldset, SIGUSR1);
633        if(ret <  0) { abort("ERROR sigismember returned %d", ret); }
634        if(ret == 1) { abort("ERROR SIGUSR1 is disabled"); }
635
636        ret = sigismember(&oldset, SIGALRM);
637        if(ret <  0) { abort("ERROR sigismember returned %d", ret); }
638        if(ret == 0) { abort("ERROR SIGALRM is enabled"); }
639
640        ret = sigismember(&oldset, SIGTERM);
641        if(ret <  0) { abort("ERROR sigismember returned %d", ret); }
642        if(ret == 1) { abort("ERROR SIGTERM is disabled"); }
643}
644
645#ifdef __CFA_WITH_VERIFY__
646bool __cfaabi_dbg_in_kernel() {
647        return !__preemption_enabled();
648}
649#endif
650
651// Local Variables: //
652// mode: c //
653// tab-width: 4 //
654// End: //
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