source: libcfa/src/concurrency/preemption.cfa @ 27f5f71

arm-ehjacob/cs343-translationjenkins-sandboxnew-astnew-ast-unique-expr
Last change on this file since 27f5f71 was 27f5f71, checked in by Peter A. Buhr <pabuhr@…>, 2 years ago

explicitly create stack for pthread thread, change NULL to 0p

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File size: 17.6 KB
Line 
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 : Sat Nov 30 08:02:56 2019
13// Update Count     : 39
14//
15
16#define __cforall_thread__
17
18#include "preemption.hfa"
19#include <assert.h>
20
21extern "C" {
22#include <errno.h>
23#include <stdio.h>
24#include <string.h>
25#include <unistd.h>
26#include <limits.h>                                                                             // PTHREAD_STACK_MIN
27}
28
29#include "bits/signal.hfa"
30
31#if !defined(__CFA_DEFAULT_PREEMPTION__)
32#define __CFA_DEFAULT_PREEMPTION__ 10`ms
33#endif
34
35Duration default_preemption() __attribute__((weak)) {
36        return __CFA_DEFAULT_PREEMPTION__;
37}
38
39// FwdDeclarations : timeout handlers
40static void preempt( processor   * this );
41static void timeout( thread_desc * this );
42
43// FwdDeclarations : Signal handlers
44static void sigHandler_ctxSwitch( __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_ARCH )
59#define CFA_REG_IP arm_pc
60#else
61#error unknown hardware architecture
62#endif
63
64KERNEL_STORAGE(event_kernel_t, event_kernel);         // private storage for event kernel
65event_kernel_t * event_kernel;                        // kernel public handle to even kernel
66static pthread_t alarm_thread;                        // pthread handle to alarm thread
67
68static void ?{}(event_kernel_t & this) with( this ) {
69        alarms{};
70        lock{};
71}
72
73enum {
74        PREEMPT_NORMAL    = 0,
75        PREEMPT_TERMINATE = 1,
76};
77
78//=============================================================================================
79// Kernel Preemption logic
80//=============================================================================================
81
82// Get next expired node
83static inline alarm_node_t * get_expired( alarm_list_t * alarms, Time currtime ) {
84        if( !alarms->head ) return 0p;                                          // If no alarms return null
85        if( alarms->head->alarm >= currtime ) return 0p;        // If alarms head not expired return null
86        return pop(alarms);                                                                     // Otherwise just pop head
87}
88
89// Tick one frame of the Discrete Event Simulation for alarms
90static void tick_preemption() {
91        alarm_node_t * node = 0p;                                                       // Used in the while loop but cannot be declared in the while condition
92        alarm_list_t * alarms = &event_kernel->alarms;          // Local copy for ease of reading
93        Time currtime = __kernel_get_time();                            // Check current time once so everything "happens at once"
94
95        //Loop throught every thing expired
96        while( node = get_expired( alarms, currtime ) ) {
97                // __cfaabi_dbg_print_buffer_decl( " KERNEL: preemption tick.\n" );
98
99                // Check if this is a kernel
100                if( node->kernel_alarm ) {
101                        preempt( node->proc );
102                }
103                else {
104                        timeout( node->thrd );
105                }
106
107                // Check if this is a periodic alarm
108                Duration period = node->period;
109                if( period > 0 ) {
110                        // __cfaabi_dbg_print_buffer_local( " KERNEL: alarm period is %lu.\n", period.tv );
111                        node->alarm = currtime + period;    // Alarm is periodic, add currtime to it (used cached current time)
112                        insert( alarms, node );             // Reinsert the node for the next time it triggers
113                }
114                else {
115                        node->set = false;                  // Node is one-shot, just mark it as not pending
116                }
117        }
118
119        // If there are still alarms pending, reset the timer
120        if( alarms->head ) {
121                __cfaabi_dbg_print_buffer_decl( " KERNEL: @%ju(%ju) resetting alarm to %ju.\n", currtime.tv, __kernel_get_time().tv, (alarms->head->alarm - currtime).tv);
122                Duration delta = alarms->head->alarm - currtime;
123                Duration caped = max(delta, 50`us);
124                // itimerval tim  = { caped };
125                // __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);
126
127                __kernel_set_timer( caped );
128        }
129}
130
131// Update the preemption of a processor and notify interested parties
132void update_preemption( processor * this, Duration duration ) {
133        alarm_node_t * alarm = this->preemption_alarm;
134
135        // Alarms need to be enabled
136        if ( duration > 0 && ! alarm->set ) {
137                alarm->alarm = __kernel_get_time() + duration;
138                alarm->period = duration;
139                register_self( alarm );
140        }
141        // Zero duration but alarm is set
142        else if ( duration == 0 && alarm->set ) {
143                unregister_self( alarm );
144                alarm->alarm = 0;
145                alarm->period = 0;
146        }
147        // If alarm is different from previous, change it
148        else if ( duration > 0 && alarm->period != duration ) {
149                unregister_self( alarm );
150                alarm->alarm = __kernel_get_time() + duration;
151                alarm->period = duration;
152                register_self( alarm );
153        }
154}
155
156//=============================================================================================
157// Kernel Signal Tools
158//=============================================================================================
159
160__cfaabi_dbg_debug_do( static thread_local void * last_interrupt = 0; )
161
162extern "C" {
163        // Disable interrupts by incrementing the counter
164        void disable_interrupts() {
165                with( kernelTLS.preemption_state ) {
166                        #if GCC_VERSION > 50000
167                        static_assert(__atomic_always_lock_free(sizeof(enabled), &enabled), "Must be lock-free");
168                        #endif
169
170                        // Set enabled flag to false
171                        // should be atomic to avoid preemption in the middle of the operation.
172                        // use memory order RELAXED since there is no inter-thread on this variable requirements
173                        __atomic_store_n(&enabled, false, __ATOMIC_RELAXED);
174
175                        // Signal the compiler that a fence is needed but only for signal handlers
176                        __atomic_signal_fence(__ATOMIC_ACQUIRE);
177
178                        __attribute__((unused)) unsigned short new_val = disable_count + 1;
179                        disable_count = new_val;
180                        verify( new_val < 65_000u );              // If this triggers someone is disabling interrupts without enabling them
181                }
182        }
183
184        // Enable interrupts by decrementing the counter
185        // If counter reaches 0, execute any pending CtxSwitch
186        void enable_interrupts( __cfaabi_dbg_ctx_param ) {
187                processor   * proc = kernelTLS.this_processor; // Cache the processor now since interrupts can start happening after the atomic store
188                thread_desc * thrd = kernelTLS.this_thread;       // Cache the thread now since interrupts can start happening after the atomic store
189
190                with( kernelTLS.preemption_state ){
191                        unsigned short prev = disable_count;
192                        disable_count -= 1;
193                        verify( prev != 0u );                     // If this triggers someone is enabled already enabled interruptsverify( prev != 0u );
194
195                        // Check if we need to prempt the thread because an interrupt was missed
196                        if( prev == 1 ) {
197                                #if GCC_VERSION > 50000
198                                static_assert(__atomic_always_lock_free(sizeof(enabled), &enabled), "Must be lock-free");
199                                #endif
200
201                                // Set enabled flag to true
202                                // should be atomic to avoid preemption in the middle of the operation.
203                                // use memory order RELAXED since there is no inter-thread on this variable requirements
204                                __atomic_store_n(&enabled, true, __ATOMIC_RELAXED);
205
206                                // Signal the compiler that a fence is needed but only for signal handlers
207                                __atomic_signal_fence(__ATOMIC_RELEASE);
208                                if( proc->pending_preemption ) {
209                                        proc->pending_preemption = false;
210                                        BlockInternal( thrd );
211                                }
212                        }
213                }
214
215                // For debugging purposes : keep track of the last person to enable the interrupts
216                __cfaabi_dbg_debug_do( proc->last_enable = caller; )
217        }
218
219        // Disable interrupts by incrementint the counter
220        // Don't execute any pending CtxSwitch even if counter reaches 0
221        void enable_interrupts_noPoll() {
222                unsigned short prev = kernelTLS.preemption_state.disable_count;
223                kernelTLS.preemption_state.disable_count -= 1;
224                verifyf( prev != 0u, "Incremented from %u\n", prev );                     // If this triggers someone is enabled already enabled interrupts
225                if( prev == 1 ) {
226                        #if GCC_VERSION > 50000
227                        static_assert(__atomic_always_lock_free(sizeof(kernelTLS.preemption_state.enabled), &kernelTLS.preemption_state.enabled), "Must be lock-free");
228                        #endif
229                        // Set enabled flag to true
230                        // should be atomic to avoid preemption in the middle of the operation.
231                        // use memory order RELAXED since there is no inter-thread on this variable requirements
232                        __atomic_store_n(&kernelTLS.preemption_state.enabled, true, __ATOMIC_RELAXED);
233
234                        // Signal the compiler that a fence is needed but only for signal handlers
235                        __atomic_signal_fence(__ATOMIC_RELEASE);
236                }
237        }
238}
239
240// sigprocmask wrapper : unblock a single signal
241static inline void signal_unblock( int sig ) {
242        sigset_t mask;
243        sigemptyset( &mask );
244        sigaddset( &mask, sig );
245
246        if ( pthread_sigmask( SIG_UNBLOCK, &mask, 0p ) == -1 ) {
247            abort( "internal error, pthread_sigmask" );
248        }
249}
250
251// sigprocmask wrapper : block a single signal
252static inline void signal_block( int sig ) {
253        sigset_t mask;
254        sigemptyset( &mask );
255        sigaddset( &mask, sig );
256
257        if ( pthread_sigmask( SIG_BLOCK, &mask, 0p ) == -1 ) {
258            abort( "internal error, pthread_sigmask" );
259        }
260}
261
262// kill wrapper : signal a processor
263static void preempt( processor * this ) {
264        sigval_t value = { PREEMPT_NORMAL };
265        pthread_sigqueue( this->kernel_thread, SIGUSR1, value );
266}
267
268// reserved for future use
269static void timeout( thread_desc * this ) {
270        //TODO : implement waking threads
271}
272
273// KERNEL ONLY
274// Check if a CtxSwitch signal handler shoud defer
275// If true  : preemption is safe
276// If false : preemption is unsafe and marked as pending
277static inline bool preemption_ready() {
278        // Check if preemption is safe
279        bool ready = kernelTLS.preemption_state.enabled && ! kernelTLS.preemption_state.in_progress;
280
281        // Adjust the pending flag accordingly
282        kernelTLS.this_processor->pending_preemption = !ready;
283        return ready;
284}
285
286//=============================================================================================
287// Kernel Signal Startup/Shutdown logic
288//=============================================================================================
289
290// Startup routine to activate preemption
291// Called from kernel_startup
292void kernel_start_preemption() {
293        __cfaabi_dbg_print_safe( "Kernel : Starting preemption\n" );
294
295        // Start with preemption disabled until ready
296        kernelTLS.preemption_state.enabled = false;
297        kernelTLS.preemption_state.disable_count = 1;
298
299        // Initialize the event kernel
300        event_kernel = (event_kernel_t *)&storage_event_kernel;
301        (*event_kernel){};
302
303        // Setup proper signal handlers
304        __cfaabi_sigaction( SIGUSR1, sigHandler_ctxSwitch, SA_SIGINFO | SA_RESTART ); // CtxSwitch handler
305
306        signal_block( SIGALRM );
307
308        pthread_attr_t attr;
309        int ret;
310        ret = pthread_attr_init( &attr );                                       // initialize attribute
311        if ( ret ) {
312                abort( "%s : internal error, pthread_attr_init failed, error(%d) %s.", __PRETTY_FUNCTION__, ret, strerror( ret ) );
313        } // if
314
315        size_t stacksize;
316        ret = pthread_attr_getstacksize( &attr, &stacksize ); // default stack size, normally defined by shell limit
317        if ( ret ) {
318                abort( "%s : internal error, pthread_attr_getstacksize failed, error(%d) %s.", __PRETTY_FUNCTION__, ret, strerror( ret ) );
319        } // if
320        assert( stacksize >= PTHREAD_STACK_MIN );
321
322        kernelTLS.preemption_state.stack = malloc( stacksize );
323        ret = pthread_attr_setstack( &attr, kernelTLS.preemption_state.stack, stacksize );
324        if ( ret ) {
325                abort( "%s : internal error, pthread_attr_setstack failed, error(%d) %s.", __PRETTY_FUNCTION__, ret, strerror( ret ) );
326        } // if
327
328        ret = pthread_create( &alarm_thread, &attr, alarm_loop, 0p );
329        if ( ret ) {
330                abort( "%s : internal error, pthread_create failed, error(%d) %s.", __PRETTY_FUNCTION__, ret, strerror( ret ) );
331        } // if
332}
333
334// Shutdown routine to deactivate preemption
335// Called from kernel_shutdown
336void kernel_stop_preemption() {
337        __cfaabi_dbg_print_safe( "Kernel : Preemption stopping\n" );
338
339        // Block all signals since we are already shutting down
340        sigset_t mask;
341        sigfillset( &mask );
342        sigprocmask( SIG_BLOCK, &mask, 0p );
343
344        // Notify the alarm thread of the shutdown
345        sigval val = { 1 };
346        pthread_sigqueue( alarm_thread, SIGALRM, val );
347
348        // Wait for the preemption thread to finish
349
350        pthread_join( alarm_thread, 0p );
351        free( kernelTLS.preemption_state.stack );
352
353        // Preemption is now fully stopped
354
355        __cfaabi_dbg_print_safe( "Kernel : Preemption stopped\n" );
356}
357
358// Raii ctor/dtor for the preemption_scope
359// Used by thread to control when they want to receive preemption signals
360void ?{}( preemption_scope & this, processor * proc ) {
361        (this.alarm){ proc, (Time){ 0 }, 0`s };
362        this.proc = proc;
363        this.proc->preemption_alarm = &this.alarm;
364
365        update_preemption( this.proc, this.proc->cltr->preemption_rate );
366}
367
368void ^?{}( preemption_scope & this ) {
369        disable_interrupts();
370
371        update_preemption( this.proc, 0`s );
372}
373
374//=============================================================================================
375// Kernel Signal Handlers
376//=============================================================================================
377
378// Context switch signal handler
379// Receives SIGUSR1 signal and causes the current thread to yield
380static void sigHandler_ctxSwitch( __CFA_SIGPARMS__ ) {
381        __cfaabi_dbg_debug_do( last_interrupt = (void *)(cxt->uc_mcontext.CFA_REG_IP); )
382
383        // SKULLDUGGERY: if a thread creates a processor and the immediately deletes it,
384        // the interrupt that is supposed to force the kernel thread to preempt might arrive
385        // before the kernel thread has even started running. When that happens an iterrupt
386        // we a null 'this_processor' will be caught, just ignore it.
387        if(! kernelTLS.this_processor ) return;
388
389        choose(sfp->si_value.sival_int) {
390                case PREEMPT_NORMAL   : ;// Normal case, nothing to do here
391                case PREEMPT_TERMINATE: verify( __atomic_load_n( &kernelTLS.this_processor->do_terminate, __ATOMIC_SEQ_CST ) );
392                default:
393                        abort( "internal error, signal value is %d", sfp->si_value.sival_int );
394        }
395
396        // Check if it is safe to preempt here
397        if( !preemption_ready() ) { return; }
398
399        __cfaabi_dbg_print_buffer_decl( " KERNEL: preempting core %p (%p @ %p).\n", kernelTLS.this_processor, kernelTLS.this_thread, (void *)(cxt->uc_mcontext.CFA_REG_IP) );
400
401        // Sync flag : prevent recursive calls to the signal handler
402        kernelTLS.preemption_state.in_progress = true;
403
404        // Clear sighandler mask before context switching.
405        #if GCC_VERSION > 50000
406        static_assert( sizeof( sigset_t ) == sizeof( cxt->uc_sigmask ), "Expected cxt->uc_sigmask to be of sigset_t" );
407        #endif
408        if ( pthread_sigmask( SIG_SETMASK, (sigset_t *)&(cxt->uc_sigmask), 0p ) == -1 ) {
409                abort( "internal error, sigprocmask" );
410        }
411
412        // TODO: this should go in finish action
413        // Clear the in progress flag
414        kernelTLS.preemption_state.in_progress = false;
415
416        // Preemption can occur here
417
418        BlockInternal( kernelTLS.this_thread ); // Do the actual CtxSwitch
419}
420
421// Main of the alarm thread
422// Waits on SIGALRM and send SIGUSR1 to whom ever needs it
423static void * alarm_loop( __attribute__((unused)) void * args ) {
424        // Block sigalrms to control when they arrive
425        sigset_t mask;
426        sigfillset(&mask);
427        if ( pthread_sigmask( SIG_BLOCK, &mask, 0p ) == -1 ) {
428            abort( "internal error, pthread_sigmask" );
429        }
430
431        sigemptyset( &mask );
432        sigaddset( &mask, SIGALRM );
433
434        // Main loop
435        while( true ) {
436                // Wait for a sigalrm
437                siginfo_t info;
438                int sig = sigwaitinfo( &mask, &info );
439
440                if( sig < 0 ) {
441                        //Error!
442                        int err = errno;
443                        switch( err ) {
444                                case EAGAIN :
445                                case EINTR :
446                                        {__cfaabi_dbg_print_buffer_decl( " KERNEL: Spurious wakeup %d.\n", err );}
447                                        continue;
448                                case EINVAL :
449                                        abort( "Timeout was invalid." );
450                                default:
451                                        abort( "Unhandled error %d", err);
452                        }
453                }
454
455                // If another signal arrived something went wrong
456                assertf(sig == SIGALRM, "Kernel Internal Error, sigwait: Unexpected signal %d (%d : %d)\n", sig, info.si_code, info.si_value.sival_int);
457
458                // __cfaabi_dbg_print_safe( "Kernel : Caught alarm from %d with %d\n", info.si_code, info.si_value.sival_int );
459                // Switch on the code (a.k.a. the sender) to
460                switch( info.si_code )
461                {
462                // Timers can apparently be marked as sent for the kernel
463                // In either case, tick preemption
464                case SI_TIMER:
465                case SI_KERNEL:
466                        // __cfaabi_dbg_print_safe( "Kernel : Preemption thread tick\n" );
467                        lock( event_kernel->lock __cfaabi_dbg_ctx2 );
468                        tick_preemption();
469                        unlock( event_kernel->lock );
470                        break;
471                // Signal was not sent by the kernel but by an other thread
472                case SI_QUEUE:
473                        // For now, other thread only signal the alarm thread to shut it down
474                        // If this needs to change use info.si_value and handle the case here
475                        goto EXIT;
476                }
477        }
478
479EXIT:
480        __cfaabi_dbg_print_safe( "Kernel : Preemption thread stopping\n" );
481        return 0p;
482}
483
484//=============================================================================================
485// Kernel Signal Debug
486//=============================================================================================
487
488void __cfaabi_check_preemption() {
489        bool ready = kernelTLS.preemption_state.enabled;
490        if(!ready) { abort("Preemption should be ready"); }
491
492        sigset_t oldset;
493        int ret;
494        ret = pthread_sigmask(0, 0p, &oldset);
495        if(ret != 0) { abort("ERROR sigprocmask returned %d", ret); }
496
497        ret = sigismember(&oldset, SIGUSR1);
498        if(ret <  0) { abort("ERROR sigismember returned %d", ret); }
499        if(ret == 1) { abort("ERROR SIGUSR1 is disabled"); }
500
501        ret = sigismember(&oldset, SIGALRM);
502        if(ret <  0) { abort("ERROR sigismember returned %d", ret); }
503        if(ret == 0) { abort("ERROR SIGALRM is enabled"); }
504
505        ret = sigismember(&oldset, SIGTERM);
506        if(ret <  0) { abort("ERROR sigismember returned %d", ret); }
507        if(ret == 1) { abort("ERROR SIGTERM is disabled"); }
508}
509
510#ifdef __CFA_WITH_VERIFY__
511bool __cfaabi_dbg_in_kernel() {
512        return !kernelTLS.preemption_state.enabled;
513}
514#endif
515
516// Local Variables: //
517// mode: c //
518// tab-width: 4 //
519// End: //
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