source: trunk/kernel/kern/scheduler.c @ 438

Last change on this file since 438 was 438, checked in by alain, 4 years ago

Fix a bug in scheduler related to RPC blocking.

File size: 13.4 KB
Line 
1/*
2 * scheduler.c - Core scheduler implementation.
3 *
4 * Author    Alain Greiner (2016)
5 *
6 * Copyright (c)  UPMC Sorbonne Universites
7 *
8 * This file is part of ALMOS-MKH.
9 *
10 * ALMOS-MKH. is free software; you can redistribute it and/or modify it
11 * under the terms of the GNU General Public License as published by
12 * the Free Software Foundation; version 2.0 of the License.
13 *
14 * ALMOS-MKH. is distributed in the hope that it will be useful, but
15 * WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17 * General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License
20 * along with ALMOS-MKH.; if not, write to the Free Software Foundation,
21 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24#include <kernel_config.h>
25#include <hal_types.h>
26#include <hal_switch.h>
27#include <hal_irqmask.h>
28#include <hal_context.h>
29#include <printk.h>
30#include <list.h>
31#include <core.h>
32#include <thread.h>
33#include <chdev.h>
34#include <scheduler.h>
35
36///////////////////////////////////////////////////////////////////////////////////////////
37// Extern global variables
38///////////////////////////////////////////////////////////////////////////////////////////
39
40extern chdev_directory_t    chdev_dir;            // allocated in kernel_init.c file
41extern uint32_t             switch_save_sr[];     // allocated in kernel_init.c file
42
43////////////////////////////////
44void sched_init( core_t * core )
45{
46    scheduler_t * sched = &core->scheduler;
47
48    sched->u_threads_nr   = 0;
49    sched->k_threads_nr   = 0;
50
51    sched->current        = CURRENT_THREAD;
52    sched->idle           = NULL;             // initialized in kernel_init()
53    sched->u_last         = NULL;             // initialized in sched_register_thread()
54    sched->k_last         = NULL;             // initialized in sched_register_thread()
55
56    // initialise threads lists
57    list_root_init( &sched->u_root );
58    list_root_init( &sched->k_root );
59
60    sched->req_ack_pending = false;           // no pending request
61
62}  // end sched_init()
63
64////////////////////////////////////////////
65void sched_register_thread( core_t   * core,
66                            thread_t * thread )
67{
68    scheduler_t * sched = &core->scheduler;
69    thread_type_t type  = thread->type;
70
71    // take lock protecting sheduler lists
72    spinlock_lock( &sched->lock );
73
74    if( type == THREAD_USER )
75    {
76        list_add_last( &sched->u_root , &thread->sched_list );
77        sched->u_threads_nr++;
78        if( sched->u_last == NULL ) sched->u_last = &thread->sched_list;
79    }
80    else // kernel thread
81    {
82        list_add_last( &sched->k_root , &thread->sched_list );
83        sched->k_threads_nr++;
84        if( sched->k_last == NULL ) sched->k_last = &thread->sched_list; 
85    }
86
87    // release lock
88    hal_fence();
89    spinlock_unlock( &sched->lock );
90
91}  // end sched_register_thread()
92
93//////////////////////////////////////////////
94thread_t * sched_select( scheduler_t * sched )
95{
96    thread_t     * thread;
97    list_entry_t * current;
98    list_entry_t * last;
99    list_entry_t * root;
100    bool_t         done;
101
102    // take lock protecting sheduler lists
103    spinlock_lock( &sched->lock );
104
105    // first : scan the kernel threads list if not empty
106    if( list_is_empty( &sched->k_root ) == false )
107    {
108        root    = &sched->k_root;
109        last    = sched->k_last;
110        current = last;
111        done    = false;
112
113        while( done == false )
114        {
115            // get next entry in kernel list
116            current = current->next;
117
118            // check exit condition
119            if( current == last ) done = true;
120
121            // skip the root that does not contain a thread
122            if( current == root ) continue;
123
124            // get thread pointer for this entry
125            thread = LIST_ELEMENT( current , thread_t , sched_list );
126
127            // execute RPC thread if non blocked
128            if( (thread->blocked == 0)  && 
129                (thread->type == THREAD_RPC) )
130            {
131                spinlock_unlock( &sched->lock );
132                return thread;
133            }
134
135            // execute DEV thread if non blocked and waiting queue non empty
136            if( (thread->blocked == 0)  &&
137                (thread->type == THREAD_DEV) &&
138                (xlist_is_empty( XPTR( local_cxy , &thread->chdev->wait_root)) == 0) ) 
139            {
140                spinlock_unlock( &sched->lock );
141                return thread;
142            }
143        } // end loop on kernel threads
144    } // end if kernel threads
145
146    // second : scan the user threads list if not empty
147    if( list_is_empty( &sched->u_root ) == false )
148    {
149        root    = &sched->u_root;
150        last    = sched->u_last;
151        current = last;
152        done    = false;
153
154        while( done == false )
155        {
156            // get next entry in user list
157            current = current->next;
158
159            // check exit condition
160            if( current == last ) done = true;
161
162            // skip the root that does not contain a thread
163            if( current == root ) continue;
164
165            // get thread pointer for this entry
166            thread = LIST_ELEMENT( current , thread_t , sched_list );
167
168            // return thread if non blocked
169            if( thread->blocked == 0 )
170            {
171                spinlock_unlock( &sched->lock );
172                return thread;
173            }
174        } // end loop on user threads
175    } // end if user threads
176
177    // third : return idle thread if no other runnable thread
178    spinlock_unlock( &sched->lock );
179    return sched->idle;
180
181}  // end sched_select()
182
183///////////////////////////////////////////
184void sched_handle_signals( core_t * core )
185{
186
187    list_entry_t * iter;
188    thread_t     * thread;
189    process_t    * process;
190
191    scheduler_t  * sched = &core->scheduler;
192
193    // take lock protecting threads lists
194    spinlock_lock( &sched->lock );
195
196    // scan all user threads
197    LIST_FOREACH( &sched->u_root , iter )
198    {
199        thread = LIST_ELEMENT( iter , thread_t , sched_list );
200
201        // handle REQ_ACK
202        if( thread->flags & THREAD_FLAG_REQ_ACK )
203        {
204            // check thread blocked
205            assert( (thread->blocked & THREAD_BLOCKED_GLOBAL) , 
206            __FUNCTION__ , "thread not blocked" );
207 
208            // decrement response counter
209            hal_atomic_add( thread->ack_rsp_count , -1 );
210
211            // reset REQ_ACK in thread descriptor
212            thread_reset_req_ack( thread );
213        }
214
215        // handle REQ_DELETE
216        if( thread->flags & THREAD_FLAG_REQ_DELETE )
217        {
218            // get thread process descriptor
219            process = thread->process;
220
221#if DEBUG_SCHED_HANDLE_SIGNALS
222uint32_t cycle = (uint32_t)hal_get_cycles();
223if( DEBUG_SCHED_HANDLE_SIGNALS < cycle )
224printk("\n[DBG] %s : thread %x in proces %x must be deleted / cycle %d\n",
225__FUNCTION__ , thread , process->pid , cycle );
226#endif
227                // release FPU if required
228                if( thread->core->fpu_owner == thread )  thread->core->fpu_owner = NULL;
229
230            // detach thread from parent if attached
231            if( (thread->flags & THREAD_FLAG_DETACHED) == 0 ) 
232            thread_child_parent_unlink( thread->parent , XPTR( local_cxy , thread ) );
233
234            // remove thread from scheduler (scheduler lock already taken)
235            uint32_t threads_nr = sched->u_threads_nr;
236            assert( (threads_nr != 0) , __FUNCTION__ , "u_threads_nr cannot be 0\n" );
237            sched->u_threads_nr = threads_nr - 1;
238            list_unlink( &thread->sched_list );
239            if( threads_nr == 1 ) sched->u_last = NULL;
240
241            // delete thread
242            thread_destroy( thread );
243
244#if DEBUG_SCHED_HANDLE_SIGNALS
245cycle = (uint32_t)hal_get_cycles();
246if( DEBUG_SCHED_HANDLE_SIGNALS < cycle )
247printk("\n[DBG] %s : thread %x in process %x has been deleted / cycle %d\n",
248__FUNCTION__ , thread , process->pid , cycle );
249#endif
250            // destroy process descriptor if no more threads
251            if( process->th_nr == 0 ) 
252            {
253                // delete process   
254                process_destroy( process );
255
256#if DEBUG_SCHED_HANDLE_SIGNALS
257cycle = (uint32_t)hal_get_cycles();
258if( DEBUG_SCHED_HANDLE_SIGNALS < cycle )
259printk("\n[DBG] %s : process %x has been deleted / cycle %d\n",
260__FUNCTION__ , process->pid , cycle );
261#endif
262
263            }
264        }
265    }
266
267    // release lock
268    hal_fence();
269    spinlock_unlock( &sched->lock );
270
271} // end sched_handle_signals()
272
273////////////////////////////////
274void sched_yield( char * cause )
275{
276    thread_t    * next;
277    thread_t    * current = CURRENT_THREAD;
278    core_t      * core    = current->core;
279    scheduler_t * sched   = &core->scheduler;
280 
281#if (DEBUG_SCHED_YIELD & 0x1)
282if( DEBUG_SCHED_YIELD < (uint32_t)hal_get_cycles() )
283sched_display( core->lid );
284#endif
285
286    // delay the yield if current thread has locks
287    if( (current->local_locks != 0) || (current->remote_locks != 0) )
288    {
289        current->flags |= THREAD_FLAG_SCHED;
290        return;
291    }
292
293    // enter critical section / save SR in current thread descriptor
294    hal_disable_irq( &CURRENT_THREAD->save_sr );
295
296    // loop on threads to select next thread
297    next = sched_select( sched );
298
299    // check next thread kernel_stack overflow
300    assert( (next->signature == THREAD_SIGNATURE),
301    __FUNCTION__ , "kernel stack overflow for thread %x\n", next );
302
303    // check next thread attached to same core as the calling thread
304    assert( (next->core == current->core),
305    __FUNCTION__ , "next core %x != current core %x\n", next->core, current->core );
306
307    // check next thread not blocked when type != IDLE
308    assert( ((next->blocked == 0) || (next->type == THREAD_IDLE)) , __FUNCTION__ ,
309    "next thread %x (%s) is blocked on core[%x,%d]\n", 
310    next->trdid , thread_type_str(next->type) , local_cxy , core->lid );
311
312    // switch contexts and update scheduler state if next != current
313        if( next != current )
314    {
315
316#if DEBUG_SCHED_YIELD
317uint32_t cycle = (uint32_t)hal_get_cycles();
318if( DEBUG_SCHED_YIELD < cycle )
319printk("\n[DBG] %s : core[%x,%d] / cause = %s\n"
320"      thread %x (%s) (%x,%x) => thread %x (%s) (%x,%x) / cycle %d\n",
321__FUNCTION__, local_cxy, core->lid, cause, 
322current, thread_type_str(current->type), current->process->pid, current->trdid,
323next , thread_type_str(next->type) , next->process->pid , next->trdid , cycle );
324#endif
325
326        // update scheduler
327        sched->current = next;
328        if( next->type == THREAD_USER ) sched->u_last = &next->sched_list;
329        else                            sched->k_last = &next->sched_list;
330
331        // handle FPU ownership
332            if( next->type == THREAD_USER )
333        {
334                if( next == current->core->fpu_owner )  hal_fpu_enable();
335                else                                    hal_fpu_disable();
336        }
337
338        // switch CPU from current thread context to new thread context
339        hal_do_cpu_switch( current->cpu_context, next->cpu_context );
340    }
341    else
342    {
343
344#if (DEBUG_SCHED_YIELD & 1)
345uint32_t cycle = (uint32_t)hal_get_cycles();
346if( DEBUG_SCHED_YIELD < cycle )
347printk("\n[DBG] %s : core[%x,%d] / cause = %s\n"
348"      thread %x (%s) (%x,%x) continue / cycle %d\n",
349__FUNCTION__, local_cxy, core->lid, cause,
350current, thread_type_str(current->type), current->process->pid, current->trdid, cycle );
351#endif
352
353    }
354
355    // handle pending requests for all threads executing on this core.
356    sched_handle_signals( core );
357
358    // exit critical section / restore SR from current thread descriptor
359    hal_restore_irq( CURRENT_THREAD->save_sr );
360
361}  // end sched_yield()
362
363
364///////////////////////////////
365void sched_display( lid_t lid )
366{
367    list_entry_t * iter;
368    thread_t     * thread;
369    uint32_t       save_sr;
370
371    assert( (lid < LOCAL_CLUSTER->cores_nr), __FUNCTION__, "illegal core index %d\n", lid);
372
373    core_t       * core    = &LOCAL_CLUSTER->core_tbl[lid];
374    scheduler_t  * sched   = &core->scheduler;
375   
376    // get pointers on TXT0 chdev
377    xptr_t    txt0_xp  = chdev_dir.txt_tx[0];
378    cxy_t     txt0_cxy = GET_CXY( txt0_xp );
379    chdev_t * txt0_ptr = GET_PTR( txt0_xp );
380
381    // get extended pointer on remote TXT0 chdev lock
382    xptr_t  lock_xp = XPTR( txt0_cxy , &txt0_ptr->wait_lock );
383
384    // get TXT0 lock in busy waiting mode
385    remote_spinlock_lock_busy( lock_xp , &save_sr );
386
387    nolock_printk("\n***** threads on core[%x,%d] / current %x / cycle %d\n",
388            local_cxy , core->lid, sched->current, (uint32_t)hal_get_cycles() );
389
390    // display kernel threads
391    LIST_FOREACH( &sched->k_root , iter )
392    {
393        thread = LIST_ELEMENT( iter , thread_t , sched_list );
394        if (thread->type == THREAD_DEV) 
395        {
396            nolock_printk(" - %s / pid %X / trdid %X / desc %X / block %X / flags %X / %s\n",
397            thread_type_str( thread->type ), thread->process->pid, thread->trdid,
398            thread, thread->blocked, thread->flags, thread->chdev->name );
399        }
400        else
401        {
402            nolock_printk(" - %s / pid %X / trdid %X / desc %X / block %X / flags %X\n",
403            thread_type_str( thread->type ), thread->process->pid, thread->trdid,
404            thread, thread->blocked, thread->flags );
405        }
406    }
407
408    // display user threads
409    LIST_FOREACH( &sched->u_root , iter )
410    {
411        thread = LIST_ELEMENT( iter , thread_t , sched_list );
412        nolock_printk(" - %s / pid %X / trdid %X / desc %X / block %X / flags %X\n",
413        thread_type_str( thread->type ), thread->process->pid, thread->trdid,
414        thread, thread->blocked, thread->flags );
415    }
416
417    // release TXT0 lock
418    remote_spinlock_unlock_busy( lock_xp , save_sr );
419
420}  // end sched_display()
421
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