source: libcfa/src/concurrency/preemption.cfa @ b81fd95

arm-ehjacob/cs343-translationnew-astnew-ast-unique-expr
Last change on this file since b81fd95 was b81fd95, checked in by Michael Brooks <mlbrooks@…>, 15 months ago

Fix bug where pointer and reference types allow unsound initialization and return. Fixes #189

There are two instances of the same basic change, which is using conversionCost instead of castCost for resolving...
A: an InitExpr?, always; affects variable initializations
B: a CastExpr?, for type-system-generated casts only; affects function returns

Changing the behaviour of the typechecker on initialization (do A) and cast (do B):
src/ResolvExpr/AlternativeFinder.cc
src/SynTree/Expression.h
testsinit1.*

Making type of string literal consistent with how C defines it (accommodate A):
src/Parser/ExpressionNode.cc

Making type system happy with incumbent use of void* (accommodate A):
libcfa/src/concurrency/kernel.cfa
libcfa/src/containers/list.hfa
tests/bugs/66.cfa
tests/avltree/avl1.cfa
tests/concurrent/signal/block.cfa
tests/searchsort.cfa

Making type system happy with incumbent plan-9 downcast (accommodate B):
libcfa/src/containers/list.hfa

Fixing previously incorrect constness of declarations (accommodate A):
tests/exceptions/defaults.cfa
libcfa/src/iostream.hfa

Fixing previously incorrect isGenerated classification of casts that desugaring introduces (accommodate B):
src/Concurrency/Keywords.cc
src/Concurrency/Waitfor.cc

Working around trac #207 (revealed by A):
tests/io2.cfa

Working around trac #208 (speculatively created by B):
libcfa/src/bits/locks.hfa
libcfa/src/concurrency/preemption.cfa

Misc:
tests/exceptions/conditional.cfa (accommodate A)

a _msg function for an exception was declared with wrong return type, so it was not compatible for assignment into the vtable instance

libcfa/src/stdlib.hfa

the compiler now prohibits a prior attempt to call a nonexistent realloc overload; calling alloc_align in its place

  • Property mode set to 100644
File size: 17.2 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 : Wed Jun 17 11:36:25 2020
13// Update Count     : 46
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
29#if !defined(__CFA_DEFAULT_PREEMPTION__)
30#define __CFA_DEFAULT_PREEMPTION__ 10`ms
31#endif
32
33Duration default_preemption() __attribute__((weak)) {
34        return __CFA_DEFAULT_PREEMPTION__;
35}
36
37// FwdDeclarations : timeout handlers
38static void preempt( processor   * this );
39static void timeout( struct __processor_id_t * id, $thread * this );
40
41// FwdDeclarations : Signal handlers
42static void sigHandler_ctxSwitch( __CFA_SIGPARMS__ );
43static void sigHandler_alarm    ( __CFA_SIGPARMS__ );
44static void sigHandler_segv     ( __CFA_SIGPARMS__ );
45static void sigHandler_ill      ( __CFA_SIGPARMS__ );
46static void sigHandler_fpe      ( __CFA_SIGPARMS__ );
47static void sigHandler_abort    ( __CFA_SIGPARMS__ );
48
49// FwdDeclarations : alarm thread main
50static void * alarm_loop( __attribute__((unused)) void * args );
51
52// Machine specific register name
53#if   defined( __i386 )
54#define CFA_REG_IP gregs[REG_EIP]
55#elif defined( __x86_64 )
56#define CFA_REG_IP gregs[REG_RIP]
57#elif defined( __ARM_ARCH )
58#define CFA_REG_IP arm_pc
59#else
60#error unknown hardware architecture
61#endif
62
63KERNEL_STORAGE(event_kernel_t, event_kernel);         // private storage for event kernel
64event_kernel_t * event_kernel;                        // kernel public handle to even kernel
65static pthread_t alarm_thread;                        // pthread handle to alarm thread
66static void * alarm_stack;                                                        // pthread stack for 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)`first ) return 0p;                                            // If no alarms return null
85        if( (*alarms)`first.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( struct __processor_id_t * id ) {
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                Duration period = node->period;
99                if( period == 0) {
100                        node->set = false;                  // Node is one-shot, just mark it as not pending
101                }
102
103                // Check if this is a kernel
104                if( node->kernel_alarm ) {
105                        preempt( node->proc );
106                }
107                else {
108                        timeout( id, node->thrd );
109                }
110
111                // Check if this is a periodic alarm
112                if( period > 0 ) {
113                        // __cfaabi_dbg_print_buffer_local( " KERNEL: alarm period is %lu.\n", period.tv );
114                        node->alarm = currtime + period;    // Alarm is periodic, add currtime to it (used cached current time)
115                        insert( alarms, node );             // Reinsert the node for the next time it triggers
116                }
117        }
118
119        // If there are still alarms pending, reset the timer
120        if( & (*alarms)`first ) {
121                __cfadbg_print_buffer_decl(preemption, " KERNEL: @%ju(%ju) resetting alarm to %ju.\n", currtime.tv, __kernel_get_time().tv, (alarms->head->alarm - currtime).tv);
122                Duration delta = (*alarms)`first.alarm - currtime;
123                Duration capped = 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( capped );
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 __cfactx_switch
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                /* paranoid */ verify( proc );
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                                        force_yield( __POLL_PREEMPTION );
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 __cfactx_switch 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( struct __processor_id_t * id, $thread * this ) {
270        #if !defined( __CFA_NO_STATISTICS__ )
271                kernelTLS.this_stats = this->curr_cluster->stats;
272        #endif
273        __unpark( id, this __cfaabi_dbg_ctx2 );
274}
275
276// KERNEL ONLY
277// Check if a __cfactx_switch signal handler shoud defer
278// If true  : preemption is safe
279// If false : preemption is unsafe and marked as pending
280static inline bool preemption_ready() {
281        // Check if preemption is safe
282        bool ready = kernelTLS.preemption_state.enabled && ! kernelTLS.preemption_state.in_progress;
283
284        // Adjust the pending flag accordingly
285        kernelTLS.this_processor->pending_preemption = !ready;
286        return ready;
287}
288
289//=============================================================================================
290// Kernel Signal Startup/Shutdown logic
291//=============================================================================================
292
293// Startup routine to activate preemption
294// Called from kernel_startup
295void kernel_start_preemption() {
296        __cfaabi_dbg_print_safe( "Kernel : Starting preemption\n" );
297
298        // Start with preemption disabled until ready
299        kernelTLS.preemption_state.enabled = false;
300        kernelTLS.preemption_state.disable_count = 1;
301
302        // Initialize the event kernel
303        event_kernel = (event_kernel_t *)&storage_event_kernel;
304        (*event_kernel){};
305
306        // Setup proper signal handlers
307        __cfaabi_sigaction( SIGUSR1, sigHandler_ctxSwitch, SA_SIGINFO | SA_RESTART ); // __cfactx_switch handler
308        __cfaabi_sigaction( SIGALRM, sigHandler_alarm    , SA_SIGINFO | SA_RESTART ); // debug handler
309
310        signal_block( SIGALRM );
311
312        alarm_stack = __create_pthread( &alarm_thread, alarm_loop, 0p );
313}
314
315// Shutdown routine to deactivate preemption
316// Called from kernel_shutdown
317void kernel_stop_preemption() {
318        __cfaabi_dbg_print_safe( "Kernel : Preemption stopping\n" );
319
320        // Block all signals since we are already shutting down
321        sigset_t mask;
322        sigfillset( &mask );
323        sigprocmask( SIG_BLOCK, &mask, 0p );
324
325        // Notify the alarm thread of the shutdown
326        sigval val = { 1 };
327        pthread_sigqueue( alarm_thread, SIGALRM, val );
328
329        // Wait for the preemption thread to finish
330
331        pthread_join( alarm_thread, 0p );
332        free( alarm_stack );
333
334        // Preemption is now fully stopped
335
336        __cfaabi_dbg_print_safe( "Kernel : Preemption stopped\n" );
337}
338
339// Raii ctor/dtor for the preemption_scope
340// Used by thread to control when they want to receive preemption signals
341void ?{}( preemption_scope & this, processor * proc ) {
342        (this.alarm){ proc, (Time){ 0 }, 0`s };
343        this.proc = proc;
344        this.proc->preemption_alarm = &this.alarm;
345
346        update_preemption( this.proc, this.proc->cltr->preemption_rate );
347}
348
349void ^?{}( preemption_scope & this ) {
350        disable_interrupts();
351
352        update_preemption( this.proc, 0`s );
353}
354
355//=============================================================================================
356// Kernel Signal Handlers
357//=============================================================================================
358
359// Context switch signal handler
360// Receives SIGUSR1 signal and causes the current thread to yield
361static void sigHandler_ctxSwitch( __CFA_SIGPARMS__ ) {
362        __cfaabi_dbg_debug_do( last_interrupt = (void *)(cxt->uc_mcontext.CFA_REG_IP); )
363
364        // SKULLDUGGERY: if a thread creates a processor and the immediately deletes it,
365        // the interrupt that is supposed to force the kernel thread to preempt might arrive
366        // before the kernel thread has even started running. When that happens an iterrupt
367        // we a null 'this_processor' will be caught, just ignore it.
368        if(! kernelTLS.this_processor ) return;
369
370        choose(sfp->si_value.sival_int) {
371                case PREEMPT_NORMAL   : ;// Normal case, nothing to do here
372                case PREEMPT_TERMINATE: verify( __atomic_load_n( &kernelTLS.this_processor->do_terminate, __ATOMIC_SEQ_CST ) );
373                default:
374                        abort( "internal error, signal value is %d", sfp->si_value.sival_int );
375        }
376
377        // Check if it is safe to preempt here
378        if( !preemption_ready() ) { return; }
379
380        __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) );
381
382        // Sync flag : prevent recursive calls to the signal handler
383        kernelTLS.preemption_state.in_progress = true;
384
385        // Clear sighandler mask before context switching.
386        #if GCC_VERSION > 50000
387        static_assert( sizeof( sigset_t ) == sizeof( cxt->uc_sigmask ), "Expected cxt->uc_sigmask to be of sigset_t" );
388        #endif
389        if ( pthread_sigmask( SIG_SETMASK, (sigset_t *)&(cxt->uc_sigmask), 0p ) == -1 ) {
390                abort( "internal error, sigprocmask" );
391        }
392
393        // TODO: this should go in finish action
394        // Clear the in progress flag
395        kernelTLS.preemption_state.in_progress = false;
396
397        // Preemption can occur here
398
399        force_yield( __ALARM_PREEMPTION ); // Do the actual __cfactx_switch
400}
401
402static void sigHandler_alarm( __CFA_SIGPARMS__ ) {
403        abort("SIGALRM should never reach the signal handler");
404}
405
406// Main of the alarm thread
407// Waits on SIGALRM and send SIGUSR1 to whom ever needs it
408static void * alarm_loop( __attribute__((unused)) void * args ) {
409        __processor_id_t id;
410        id.id = doregister(&id);
411
412        // Block sigalrms to control when they arrive
413        sigset_t mask;
414        sigfillset(&mask);
415        if ( pthread_sigmask( SIG_BLOCK, &mask, 0p ) == -1 ) {
416            abort( "internal error, pthread_sigmask" );
417        }
418
419        sigemptyset( &mask );
420        sigaddset( &mask, SIGALRM );
421
422        // Main loop
423        while( true ) {
424                // Wait for a sigalrm
425                siginfo_t info;
426                int sig = sigwaitinfo( &mask, &info );
427
428                if( sig < 0 ) {
429                        //Error!
430                        int err = errno;
431                        switch( err ) {
432                                case EAGAIN :
433                                case EINTR :
434                                        {__cfaabi_dbg_print_buffer_decl( " KERNEL: Spurious wakeup %d.\n", err );}
435                                        continue;
436                                case EINVAL :
437                                        abort( "Timeout was invalid." );
438                                default:
439                                        abort( "Unhandled error %d", err);
440                        }
441                }
442
443                // If another signal arrived something went wrong
444                assertf(sig == SIGALRM, "Kernel Internal Error, sigwait: Unexpected signal %d (%d : %d)\n", sig, info.si_code, info.si_value.sival_int);
445
446                // __cfaabi_dbg_print_safe( "Kernel : Caught alarm from %d with %d\n", info.si_code, info.si_value.sival_int );
447                // Switch on the code (a.k.a. the sender) to
448                switch( info.si_code )
449                {
450                // Timers can apparently be marked as sent for the kernel
451                // In either case, tick preemption
452                case SI_TIMER:
453                case SI_KERNEL:
454                        // __cfaabi_dbg_print_safe( "Kernel : Preemption thread tick\n" );
455                        lock( event_kernel->lock __cfaabi_dbg_ctx2 );
456                        tick_preemption( &id );
457                        unlock( event_kernel->lock );
458                        break;
459                // Signal was not sent by the kernel but by an other thread
460                case SI_QUEUE:
461                        // For now, other thread only signal the alarm thread to shut it down
462                        // If this needs to change use info.si_value and handle the case here
463                        goto EXIT;
464                }
465        }
466
467EXIT:
468        __cfaabi_dbg_print_safe( "Kernel : Preemption thread stopping\n" );
469        unregister(&id);
470        return 0p;
471}
472
473//=============================================================================================
474// Kernel Signal Debug
475//=============================================================================================
476
477void __cfaabi_check_preemption() {
478        bool ready = kernelTLS.preemption_state.enabled;
479        if(!ready) { abort("Preemption should be ready"); }
480
481        sigset_t oldset;
482        int ret;
483        ret = pthread_sigmask(0, ( const sigset_t * ) 0p, &oldset);  // workaround trac#208: cast should be unnecessary
484        if(ret != 0) { abort("ERROR sigprocmask returned %d", ret); }
485
486        ret = sigismember(&oldset, SIGUSR1);
487        if(ret <  0) { abort("ERROR sigismember returned %d", ret); }
488        if(ret == 1) { abort("ERROR SIGUSR1 is disabled"); }
489
490        ret = sigismember(&oldset, SIGALRM);
491        if(ret <  0) { abort("ERROR sigismember returned %d", ret); }
492        if(ret == 0) { abort("ERROR SIGALRM is enabled"); }
493
494        ret = sigismember(&oldset, SIGTERM);
495        if(ret <  0) { abort("ERROR sigismember returned %d", ret); }
496        if(ret == 1) { abort("ERROR SIGTERM is disabled"); }
497}
498
499#ifdef __CFA_WITH_VERIFY__
500bool __cfaabi_dbg_in_kernel() {
501        return !kernelTLS.preemption_state.enabled;
502}
503#endif
504
505// Local Variables: //
506// mode: c //
507// tab-width: 4 //
508// End: //
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