source: src/libcfa/concurrency/preemption.c @ b10affd

aaron-thesisarm-ehcleanup-dtorsdeferred_resndemanglerjacob/cs343-translationjenkins-sandboxnew-astnew-ast-unique-exprnew-envno_listpersistent-indexerwith_gc
Last change on this file since b10affd was b10affd, checked in by Peter A. Buhr <pabuhr@…>, 4 years ago

thread-local storage converted to structure and thread-local macros for access

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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 : Fri Mar 30 17:27:43 2018
13// Update Count     : 31
14//
15
16#include "preemption.h"
17
18extern "C" {
19#include <errno.h>
20#include <stdio.h>
21#include <string.h>
22#include <unistd.h>
23}
24
25#include "bits/cfatime.h"
26#include "bits/signal.h"
27
28#if !defined(__CFA_DEFAULT_PREEMPTION__)
29#define __CFA_DEFAULT_PREEMPTION__ 10`ms
30#endif
31
32Duration default_preemption() __attribute__((weak)) {
33        return __CFA_DEFAULT_PREEMPTION__;
34}
35
36// FwdDeclarations : timeout handlers
37static void preempt( processor   * this );
38static void timeout( thread_desc * this );
39
40// FwdDeclarations : Signal handlers
41void sigHandler_ctxSwitch( __CFA_SIGPARMS__ );
42void sigHandler_segv     ( __CFA_SIGPARMS__ );
43void sigHandler_ill      ( __CFA_SIGPARMS__ );
44void sigHandler_fpe      ( __CFA_SIGPARMS__ );
45void sigHandler_abort    ( __CFA_SIGPARMS__ );
46
47// FwdDeclarations : alarm thread main
48void * alarm_loop( __attribute__((unused)) void * args );
49
50// Machine specific register name
51#if   defined( __i386 )
52#define CFA_REG_IP gregs[REG_EIP]
53#elif defined( __x86_64 )
54#define CFA_REG_IP gregs[REG_RIP]
55#elif defined( __ARM_ARCH )
56#define CFA_REG_IP arm_pc
57#else
58#error unknown hardware architecture
59#endif
60
61KERNEL_STORAGE(event_kernel_t, event_kernel);         // private storage for event kernel
62event_kernel_t * event_kernel;                        // kernel public handle to even kernel
63static pthread_t alarm_thread;                        // pthread handle to alarm thread
64
65void ?{}(event_kernel_t & this) with( this ) {
66        alarms{};
67        lock{};
68}
69
70enum {
71        PREEMPT_NORMAL    = 0,
72        PREEMPT_TERMINATE = 1,
73};
74
75//=============================================================================================
76// Kernel Preemption logic
77//=============================================================================================
78
79// Get next expired node
80static inline alarm_node_t * get_expired( alarm_list_t * alarms, Time currtime ) {
81        if( !alarms->head ) return NULL;                          // If no alarms return null
82        if( alarms->head->alarm >= currtime ) return NULL;        // If alarms head not expired return null
83        return pop(alarms);                                       // Otherwise just pop head
84}
85
86// Tick one frame of the Discrete Event Simulation for alarms
87void tick_preemption() {
88        alarm_node_t * node = NULL;                     // Used in the while loop but cannot be declared in the while condition
89        alarm_list_t * alarms = &event_kernel->alarms;  // Local copy for ease of reading
90        Time currtime = __kernel_get_time();                    // Check current time once so we everything "happens at once"
91
92        //Loop throught every thing expired
93        while( node = get_expired( alarms, currtime ) ) {
94
95                // Check if this is a kernel
96                if( node->kernel_alarm ) {
97                        preempt( node->proc );
98                }
99                else {
100                        timeout( node->thrd );
101                }
102
103                // Check if this is a periodic alarm
104                Duration period = node->period;
105                if( period > 0 ) {
106                        node->alarm = currtime + period;    // Alarm is periodic, add currtime to it (used cached current time)
107                        insert( alarms, node );             // Reinsert the node for the next time it triggers
108                }
109                else {
110                        node->set = false;                  // Node is one-shot, just mark it as not pending
111                }
112        }
113
114        // If there are still alarms pending, reset the timer
115        if( alarms->head ) { __kernel_set_timer( alarms->head->alarm - currtime ); }
116}
117
118// Update the preemption of a processor and notify interested parties
119void update_preemption( processor * this, Duration duration ) {
120        alarm_node_t * alarm = this->preemption_alarm;
121
122        // Alarms need to be enabled
123        if ( duration > 0 && ! alarm->set ) {
124                alarm->alarm = __kernel_get_time() + duration;
125                alarm->period = duration;
126                register_self( alarm );
127        }
128        // Zero duraction but alarm is set
129        else if ( duration == 0 && alarm->set ) {
130                unregister_self( alarm );
131                alarm->alarm = 0;
132                alarm->period = 0;
133        }
134        // If alarm is different from previous, change it
135        else if ( duration > 0 && alarm->period != duration ) {
136                unregister_self( alarm );
137                alarm->alarm = __kernel_get_time() + duration;
138                alarm->period = duration;
139                register_self( alarm );
140        }
141}
142
143//=============================================================================================
144// Kernel Signal Tools
145//=============================================================================================
146
147__cfaabi_dbg_debug_do( static thread_local void * last_interrupt = 0; )
148
149extern "C" {
150        // Disable interrupts by incrementing the counter
151        void disable_interrupts() {
152                TL_GET( preemption_state ).enabled = false;
153                __attribute__((unused)) unsigned short new_val = TL_GET( preemption_state ).disable_count + 1;
154                TL_GET( preemption_state ).disable_count = new_val;
155                verify( new_val < 65_000u );              // If this triggers someone is disabling interrupts without enabling them
156        }
157
158        // Enable interrupts by decrementing the counter
159        // If counter reaches 0, execute any pending CtxSwitch
160        void enable_interrupts( __cfaabi_dbg_ctx_param ) {
161                processor   * proc = TL_GET( this_processor ); // Cache the processor now since interrupts can start happening after the atomic add
162                thread_desc * thrd = TL_GET( this_thread );       // Cache the thread now since interrupts can start happening after the atomic add
163
164                unsigned short prev = TL_GET( preemption_state ).disable_count;
165                TL_GET( preemption_state ).disable_count -= 1;
166                verify( prev != 0u );                     // If this triggers someone is enabled already enabled interruptsverify( prev != 0u );
167
168                // Check if we need to prempt the thread because an interrupt was missed
169                if( prev == 1 ) {
170                        TL_GET( preemption_state ).enabled = true;
171                        if( proc->pending_preemption ) {
172                                proc->pending_preemption = false;
173                                BlockInternal( thrd );
174                        }
175                }
176
177                // For debugging purposes : keep track of the last person to enable the interrupts
178                __cfaabi_dbg_debug_do( proc->last_enable = caller; )
179        }
180
181        // Disable interrupts by incrementint the counter
182        // Don't execute any pending CtxSwitch even if counter reaches 0
183        void enable_interrupts_noPoll() {
184                unsigned short prev = TL_GET( preemption_state ).disable_count;
185                TL_GET( preemption_state ).disable_count -= 1;
186                verifyf( prev != 0u, "Incremented from %u\n", prev );                     // If this triggers someone is enabled already enabled interrupts
187                if( prev == 1 ) {
188                        TL_GET( preemption_state ).enabled = true;
189                }
190        }
191}
192
193// sigprocmask wrapper : unblock a single signal
194static inline void signal_unblock( int sig ) {
195        sigset_t mask;
196        sigemptyset( &mask );
197        sigaddset( &mask, sig );
198
199        if ( pthread_sigmask( SIG_UNBLOCK, &mask, NULL ) == -1 ) {
200            abort( "internal error, pthread_sigmask" );
201        }
202}
203
204// sigprocmask wrapper : block a single signal
205static inline void signal_block( int sig ) {
206        sigset_t mask;
207        sigemptyset( &mask );
208        sigaddset( &mask, sig );
209
210        if ( pthread_sigmask( SIG_BLOCK, &mask, NULL ) == -1 ) {
211            abort( "internal error, pthread_sigmask" );
212        }
213}
214
215// kill wrapper : signal a processor
216static void preempt( processor * this ) {
217        sigval_t value = { PREEMPT_NORMAL };
218        pthread_sigqueue( this->kernel_thread, SIGUSR1, value );
219}
220
221// kill wrapper : signal a processor
222void terminate(processor * this) {
223        this->do_terminate = true;
224        sigval_t value = { PREEMPT_TERMINATE };
225        pthread_sigqueue( this->kernel_thread, SIGUSR1, value );
226}
227
228// reserved for future use
229static void timeout( thread_desc * this ) {
230        //TODO : implement waking threads
231}
232
233
234// Check if a CtxSwitch signal handler shoud defer
235// If true  : preemption is safe
236// If false : preemption is unsafe and marked as pending
237static inline bool preemption_ready() {
238        bool ready = TL_GET( preemption_state ).enabled && !TL_GET( preemption_state ).in_progress; // Check if preemption is safe
239        TL_GET( this_processor )->pending_preemption = !ready;                  // Adjust the pending flag accordingly
240        return ready;
241}
242
243//=============================================================================================
244// Kernel Signal Startup/Shutdown logic
245//=============================================================================================
246
247// Startup routine to activate preemption
248// Called from kernel_startup
249void kernel_start_preemption() {
250        __cfaabi_dbg_print_safe( "Kernel : Starting preemption\n" );
251
252        // Start with preemption disabled until ready
253        TL_GET( preemption_state ).enabled = false;
254        TL_GET( preemption_state ).disable_count = 1;
255
256        // Initialize the event kernel
257        event_kernel = (event_kernel_t *)&storage_event_kernel;
258        (*event_kernel){};
259
260        // Setup proper signal handlers
261        __cfaabi_sigaction( SIGUSR1, sigHandler_ctxSwitch, SA_SIGINFO | SA_RESTART );         // CtxSwitch handler
262
263        signal_block( SIGALRM );
264
265        pthread_create( &alarm_thread, NULL, alarm_loop, NULL );
266}
267
268// Shutdown routine to deactivate preemption
269// Called from kernel_shutdown
270void kernel_stop_preemption() {
271        __cfaabi_dbg_print_safe( "Kernel : Preemption stopping\n" );
272
273        // Block all signals since we are already shutting down
274        sigset_t mask;
275        sigfillset( &mask );
276        sigprocmask( SIG_BLOCK, &mask, NULL );
277
278        // Notify the alarm thread of the shutdown
279        sigval val = { 1 };
280        pthread_sigqueue( alarm_thread, SIGALRM, val );
281
282        // Wait for the preemption thread to finish
283        pthread_join( alarm_thread, NULL );
284
285        // Preemption is now fully stopped
286
287        __cfaabi_dbg_print_safe( "Kernel : Preemption stopped\n" );
288}
289
290// Raii ctor/dtor for the preemption_scope
291// Used by thread to control when they want to receive preemption signals
292void ?{}( preemption_scope & this, processor * proc ) {
293        (this.alarm){ proc, (Time){ 0 }, 0`s };
294        this.proc = proc;
295        this.proc->preemption_alarm = &this.alarm;
296
297        update_preemption( this.proc, this.proc->cltr->preemption_rate );
298}
299
300void ^?{}( preemption_scope & this ) {
301        disable_interrupts();
302
303        update_preemption( this.proc, 0`s );
304}
305
306//=============================================================================================
307// Kernel Signal Handlers
308//=============================================================================================
309
310// Context switch signal handler
311// Receives SIGUSR1 signal and causes the current thread to yield
312void sigHandler_ctxSwitch( __CFA_SIGPARMS__ ) {
313        __cfaabi_dbg_debug_do( last_interrupt = (void *)(cxt->uc_mcontext.CFA_REG_IP); )
314
315        // SKULLDUGGERY: if a thread creates a processor and the immediately deletes it,
316        // the interrupt that is supposed to force the kernel thread to preempt might arrive
317        // before the kernel thread has even started running. When that happens an iterrupt
318        // we a null 'this_processor' will be caught, just ignore it.
319        if(!TL_GET( this_processor )) return;
320
321        choose(sfp->si_value.sival_int) {
322                case PREEMPT_NORMAL   : ;// Normal case, nothing to do here
323                case PREEMPT_TERMINATE: verify(TL_GET( this_processor )->do_terminate);
324                default:
325                        abort( "internal error, signal value is %d", sfp->si_value.sival_int );
326        }
327
328        // Check if it is safe to preempt here
329        if( !preemption_ready() ) { return; }
330
331        __cfaabi_dbg_print_buffer_decl( " KERNEL: preempting core %p (%p).\n", this_processor, this_thread);
332
333        TL_GET( preemption_state ).in_progress = true;  // Sync flag : prevent recursive calls to the signal handler
334        signal_unblock( SIGUSR1 );                          // We are about to CtxSwitch out of the signal handler, let other handlers in
335        TL_GET( preemption_state ).in_progress = false; // Clear the in progress flag
336
337        // Preemption can occur here
338
339        BlockInternal( (thread_desc*)TL_GET( this_thread ) ); // Do the actual CtxSwitch
340}
341
342// Main of the alarm thread
343// Waits on SIGALRM and send SIGUSR1 to whom ever needs it
344void * alarm_loop( __attribute__((unused)) void * args ) {
345        // Block sigalrms to control when they arrive
346        sigset_t mask;
347        sigemptyset( &mask );
348        sigaddset( &mask, SIGALRM );
349
350        if ( pthread_sigmask( SIG_BLOCK, &mask, NULL ) == -1 ) {
351            abort( "internal error, pthread_sigmask" );
352        }
353
354        // Main loop
355        while( true ) {
356                // Wait for a sigalrm
357                siginfo_t info;
358                int sig = sigwaitinfo( &mask, &info );
359
360                if( sig < 0 ) {
361                        //Error!
362                        int err = errno;
363                        switch( err ) {
364                                case EAGAIN :
365                                case EINTR :
366                                        continue;
367                        case EINVAL :
368                                        abort( "Timeout was invalid." );
369                                default:
370                                        abort( "Unhandled error %d", err);
371                        }
372                }
373
374                // If another signal arrived something went wrong
375                assertf(sig == SIGALRM, "Kernel Internal Error, sigwait: Unexpected signal %d (%d : %d)\n", sig, info.si_code, info.si_value.sival_int);
376
377                // __cfaabi_dbg_print_safe( "Kernel : Caught alarm from %d with %d\n", info.si_code, info.si_value.sival_int );
378                // Switch on the code (a.k.a. the sender) to
379                switch( info.si_code )
380                {
381                // Timers can apparently be marked as sent for the kernel
382                // In either case, tick preemption
383                case SI_TIMER:
384                case SI_KERNEL:
385                        // __cfaabi_dbg_print_safe( "Kernel : Preemption thread tick\n" );
386                        lock( event_kernel->lock __cfaabi_dbg_ctx2 );
387                        tick_preemption();
388                        unlock( event_kernel->lock );
389                        break;
390                // Signal was not sent by the kernel but by an other thread
391                case SI_QUEUE:
392                        // For now, other thread only signal the alarm thread to shut it down
393                        // If this needs to change use info.si_value and handle the case here
394                        goto EXIT;
395                }
396        }
397
398EXIT:
399        __cfaabi_dbg_print_safe( "Kernel : Preemption thread stopping\n" );
400        return NULL;
401}
402
403// Local Variables: //
404// mode: c //
405// tab-width: 4 //
406// End: //
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