source: trunk/kernel/kern/process.h @ 453

Last change on this file since 453 was 450, checked in by alain, 6 years ago

Fix a bug in function sched_handle_signal():
When the deleted user thread is the last executed thread,
the sched->u_last field must be updated to point on another user thread.
File size: 36.2 KB
Line 
1/*
2 * process.h - process related management functions
3 *
4 * Authors  Ghassan Almaless (2008,2009,2010,2011,2012)
5 *          Mohamed Lamine Karaoui (2015)
6 *          Alain Greiner (2016,2017,2018)
7 *
8 * Copyright (c) UPMC Sorbonne Universites
9 *
10 * This file is part of ALMOS-MKH.
11 *
12 * ALMOS-MKH is free software; you can redistribute it and/or modify it
13 * under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; version 2.0 of the License.
15 *
16 * ALMOS-MKH is distributed in the hope that it will be useful, but
17 * WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
19 * General Public License for more details.
20 *
21 * You should have received a copy of the GNU General Public License
22 * along with ALMOS-MKH; if not, write to the Free Software Foundation,
23 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
24 */
25
26#ifndef _PROCESS_H_
27#define _PROCESS_H_
28
29#include <kernel_config.h>
30#include <errno.h>
31#include <hal_types.h>
32#include <list.h>
33#include <xlist.h>
34#include <bits.h>
35#include <spinlock.h>
36#include <hal_atomic.h>
37#include <vmm.h>
38#include <cluster.h>
39#include <vfs.h>
40
41/****  Forward declarations  ****/
42
43struct thread_s;
44
45/*********************************************************************************************
46 * These macros are used to compose or decompose global process identifier (PID)
47 * to or from cluster identifier / local process index (CXY , LPID)
48 ********************************************************************************************/
49
50#define LPID_FROM_PID( pid )       (lpid_t)(pid & 0x0000FFFF)
51#define CXY_FROM_PID( pid )        (cxy_t)(pid >> 16)
52#define PID( cxy , lpid )          (pid_t)((cxy << 16) | lpid )
53
54/*********************************************************************************************
55 * This enum defines the actions that can be executed by the process_sigaction() function.
56 ********************************************************************************************/
57
58enum process_sigactions
59{
60    BLOCK_ALL_THREADS    = 0x11,
61    UNBLOCK_ALL_THREADS  = 0x22,
62    DELETE_ALL_THREADS   = 0x33, 
63};
64
65/*********************************************************************************************
66 * This structure defines an array of extended pointers on the open file descriptors
67 * for a given process. We use an extended pointer because the open file descriptor
68 * is always stored in the same cluster as the inode associated to the file.
69 * A free entry in this array contains the XPTR_NULL value.
70 * The array size is defined by a the CONFIG_PROCESS_FILE_MAX_NR parameter.
71 * All modifications (open/close) in this structure must be done by the reference cluster,
72 * and reported in process copies.
73 ********************************************************************************************/
74
75typedef struct fd_array_s
76{
77        remote_spinlock_t lock;                               /*! lock protecting fd_array      */
78    uint32_t          current;                            /*! current number of open files  */
79        xptr_t            array[CONFIG_PROCESS_FILE_MAX_NR];  /*! xptr on open file descriptors */
80}
81fd_array_t;
82
83/*********************************************************************************************
84 * This structure defines a process descriptor.
85 * A process is identified by a unique PID (process identifier):
86 * - The PID 16 LSB bits contain the LPID (Local Process Index)
87 * - The PID 16 MSB bits contain the owner cluster CXY.
88 * In each cluster, the process manager allocates  the LPID values for the process that
89 * are owned by this cluster.
90 * The process descriptor is replicated in all clusters containing at least one thread
91 * of the PID process, with the following rules :
92 * 1) The <pid>, <ppid>, <ref_xp>, <owner_xp>, <vfs_root_xp>, <vfs_bin_xp>  fields are
93 *    defined in all process descriptor copies.
94 * 2) The <vfs_cwd_xp> and associated <cwd_lock>, that can be dynamically modified,
95 *    are only defined in the reference process descriptor.
96 * 2) The <vmm>, containing the VSL (list of registered vsegs), and the GPT (generic
97 *    page table), are only complete in the reference process cluster, other copies
98 *    are actually use as read-only caches.
99 * 3) the <fd_array>, containing extended pointers on the open file descriptors, is only
100 *    complete in the reference process cluster, other copies are read-only caches.
101 * 4) The <sem_root>, <mutex_root>, <barrier_root>, <condvar_root>, and the associated
102 *    <sync_lock>, that are dynamically allocated, are only defined in the reference cluster.
103 * 5) The <children_root>, <children_nr>, <children_list>, and <txt_list> fields are only
104 *    defined in the reference cluster, and are undefined in other clusters.
105 * 6) The <local_list>, <copies_list>, <th_tbl>, <th_nr>, <th_lock> fields
106 *    are defined in all process descriptors copies.
107 * 7) The termination <flags> and <exit_status> are only defined in the reference cluster.
108 *    The term_state format is defined in the shared_syscalls.h file.
109 ********************************************************************************************/
110
111typedef struct process_s
112{
113        vmm_t             vmm;              /*! embedded virtual memory manager                 */
114
115        fd_array_t        fd_array;         /*! embedded open file descriptors array            */
116
117        xptr_t            vfs_root_xp;      /*! extended pointer on current VFS root inode      */
118        xptr_t            vfs_bin_xp;       /*! extended pointer on .elf file descriptor        */
119        pid_t             pid;              /*! process identifier                              */
120    xptr_t            ref_xp;           /*! extended pointer on reference process           */
121    xptr_t            owner_xp;         /*! extended pointer on owner process               */
122    xptr_t            parent_xp;        /*! extended pointer on parent process              */
123
124        xptr_t            vfs_cwd_xp;       /*! extended pointer on current working dir inode   */
125        remote_rwlock_t   cwd_lock;         /*! lock protecting working directory changes       */
126
127        xlist_entry_t     children_root;    /*! root of the children process xlist              */
128    remote_spinlock_t children_lock;    /*! lock protecting children process xlist          */
129    uint32_t          children_nr;      /*! number of children processes                    */
130
131        xlist_entry_t     children_list;    /*! member of list of children of same parent       */
132    xlist_entry_t     local_list;       /*! member of list of process in same cluster       */
133    xlist_entry_t     copies_list;      /*! member of list of copies of same process        */
134    xlist_entry_t     txt_list;         /*! member of list of processes sharing same TXT    */
135
136        spinlock_t        th_lock;          /*! lock protecting th_tbl[] concurrent access      */
137        uint32_t          th_nr;            /*! number of threads in this cluster               */
138
139        struct thread_s * th_tbl[CONFIG_THREAD_MAX_PER_CLUSTER]; /*! pointers on local threads  */
140
141    xlist_entry_t     sem_root;         /*! root of the process semaphore list              */
142    xlist_entry_t     mutex_root;       /*! root of the process mutex list                  */
143    xlist_entry_t     barrier_root;     /*! root of the process barrier list                */
144    xlist_entry_t     condvar_root;     /*! root of the process condvar list                */
145    remote_spinlock_t sync_lock;        /*! lock protecting sem,mutex,barrier,condvar lists */
146
147    uint32_t          term_state;       /*! termination status (flags & exit status)        */
148
149    bool_t            txt_owner;        /*! current TXT owner                               */
150}
151process_t;
152
153/*********************************************************************************************
154 * This structure defines the information required by the process_make_exec() function
155 * to create a new reference process descriptor, and the associated main thread.
156 ********************************************************************************************/
157
158typedef struct exec_info_s
159{
160    char               path[CONFIG_VFS_MAX_PATH_LENGTH];   /*!  .elf file path              */
161
162    char            ** args_pointers;  /*! physical base address of array of pointers       */
163    char             * args_buf_base;  /*! physical base address of kernel args buffer      */
164    uint32_t           args_nr;        /*! actual number of arguments                       */
165
166    char            ** envs_pointers;  /*! physical base address of array of pointers       */
167    char             * envs_buf_base;  /*! physical base address of kernel args buffer      */
168    char             * envs_buf_free;  /*! physical address of first free slot in envs_buf  */
169    uint32_t           envs_nr;        /*! actual number of environment variables           */
170}
171exec_info_t;
172
173/***************   Process Descriptor Operations    *****************************************/
174
175/*********************************************************************************************
176 * This function allocates memory in local cluster for a process descriptor.
177 *********************************************************************************************
178 * @ returns pointer on process descriptor if success / return NULL if failure
179 ********************************************************************************************/
180process_t * process_alloc();
181
182/*********************************************************************************************
183 * This function releases memory in local cluster for a process descriptor.
184 *********************************************************************************************
185 * @ process      : pointer on process descriptor to release.
186 ********************************************************************************************/
187void process_free( process_t * process );
188
189/*********************************************************************************************
190 * This function initialize, in each cluster, the kernel "process_zero", that is the owner
191 * of all kernel threads in a given cluster. It is called by the kernel_init() function.
192 * The process_zero descriptor is allocated as a global variable in file kernel_init.c
193 * Both the PID and PPID fields are set to zero, the ref_xp is the local process_zero,
194 * and the parent process is set to XPTR_NULL. The th_tbl[] is initialized as empty.
195 *********************************************************************************************
196 * @ process      : [in] pointer on local process descriptor to initialize.
197 ********************************************************************************************/
198void process_zero_create( process_t * process );
199
200/*********************************************************************************************
201 * This function allocates memory and initializes the "process_init" descriptor and the
202 * associated "thread_init" descriptor. It is called once at the end of the kernel
203 * initialisation procedure. Its local process identifier is 1, and parent process
204 * is the kernel process in cluster 0.
205 * The "process_init" is the first user process, and all other user processes will be forked
206 * from this process. The code executed by "process_init" is stored in a .elf file, whose
207 * pathname is defined by the CONFIG_PROCESS_INIT_PATH configuration variable.
208 * The process_init does not use the [STDIN/STDOUT/STDERR] streams, but it is linked
209 * to kernel TXT0, because these streams must be defined for all user processes.
210 ********************************************************************************************/
211void process_init_create();
212
213/*********************************************************************************************
214 * This function initializes a local, reference, user process descriptor from another process
215 * descriptor, defined by the <model_xp> argument. The <process> and <pid> arguments must
216 * be previously allocated by he caller. This function can be called by three functions:
217 * 1) process_init_create() : process is the reference INIT process / pid = 1 /
218 *    the parent and model process descriptors are both the kernel process_zero.
219 * 2) process_make_fork() : the model process descriptor is the (generally remote)
220 *    parent process.
221 * 3) process_make exec() : the model process is the local old_process, the new_process
222 *    parent is the same as the old_process parent.
223 * The following fields are initialised :
224 * - It set the pid / ppid / ref_xp / parent_xp / state fields.
225 * - It initializes the VMM (register the kentry, args, envs vsegs in VSL)
226 * - It initializes the FDT, defining the three pseudo files STDIN / STDOUT / STDERR.
227 * - It set the root_xp, bin_xp, cwd_xp fields.
228 * - It reset the children list as empty, but does NOT register it in parent children list.
229 * - It reset the TH_TBL list of threads as empty.
230 * - It reset the semaphore / mutex / barrier / condvar lists as empty.
231 * - It registers the process in the local_list, rooted in the local cluster manager.
232 * - It registers the process in the copies_list, rooted in the owner cluster manager.
233 * - It registers the process extended pointer in the local pref_tbl[] array.
234 *********************************************************************************************
235 * @ process      : [in] pointer on local process descriptor to initialize.
236 * @ pid          : [in] process identifier.
237 * @ parent_xp    : [in] extended pointer on parent process descriptor.
238 * @ model_xp     : [in] extended pointer on model process descriptor.
239 ********************************************************************************************/
240void process_reference_init( process_t * process,
241                             pid_t       pid,
242                             xptr_t      parent_xp,
243                             xptr_t      model_xp );
244
245/*********************************************************************************************
246 * This function initializes a copy process descriptor, in the local cluster,
247 * from information defined in the reference remote process descriptor.
248 *********************************************************************************************
249 * @ process              : [in] local pointer on process descriptor to initialize.
250 * @ reference_process_xp : [in] extended pointer on reference process descriptor.
251 * @ return 0 if success / return ENOMEM if failure
252 ********************************************************************************************/
253error_t process_copy_init( process_t * local_process,
254                           xptr_t      reference_process_xp );
255
256/*********************************************************************************************
257 * This function releases all memory allocated for a process descriptor in the local cluster,
258 * including memory allocated for embedded substructures (fd_array, vmm, etc).
259 * The local th_tbl[] array must be empty.
260 *********************************************************************************************
261 * @ process     : pointer on the process descriptor.
262 ********************************************************************************************/
263void process_destroy( process_t * process );
264
265/*********************************************************************************************
266 * This debug function diplays on the kernel terminal TXT0 detailed informations on a
267 * process descriptor identified by the <process_xp> argument.
268 * It can be called by a thread running in any cluster.
269 * WARNING: this function uses the nolock_printk() function, and the  TXT0 lock MUST be
270 * taken by the caller function.
271 *********************************************************************************************
272 * @ process_xp : extended pointer on process descriptor.
273 ********************************************************************************************/
274void process_display( xptr_t process_xp );
275
276/*********************************************************************************************
277 * This function returns a printable string defining the sigaction type.
278 *********************************************************************************************
279 * @ sigaction_type   : BLOCK_ALL_THREADS / UNBLOCK_ALL_THREADS / DELETE_ALL_THREADS
280 * @ return a string pointer.
281 ********************************************************************************************/
282char * process_action_str( uint32_t sigaction_type );
283
284/*********************************************************************************************
285 * This function allows a client thread running in any cluster to block, unblock or delete
286 * all threads of a process identified by the <pid> argument, depending on the
287 * <action_type> argument.
288 * WARNING : the DELETE and BLOCK actions are NOT executed on the target process main thread
289 * (thread 0 in process owner cluster), and not executed on the calling thread itself.
290 * It uses the multicast, non blocking rpc_process_sigaction_client() function to send
291 * parallel requests to all remote clusters containing process copies.
292 * Then it blocks and deschedule to wait completion of these parallel requests.
293 *
294 * It is used by the sys_kill() & sys_exit() functions to handle the "kill" & "exit" syscalls.
295 * It is also used by the process_make_exec() function to handle the "exec" syscall.
296 * It is also called by the TXT device ISR to execute the ctrl C & ctrl Z commands.
297 *
298 * Implementation note:
299 * This function allocates a - shared - RPC descriptor in client thread stack,
300 * and initializes it. This RPC descriptor can be shared because all parallel,
301 * non-blocking, RPC server threads use the same input arguments, including the
302 * RPC responses counter field.
303 *********************************************************************************************
304 * @ pid         : target process identifier.
305 * @ action_type : BLOCK_ALL_THREADS / UNBLOCK_ALL_THREADS / DELETE_ALL_THREADS
306 ********************************************************************************************/
307void process_sigaction( pid_t       pid,
308                        uint32_t    action_type );
309
310/*********************************************************************************************
311 * This function blocks all threads for a given <process> in the local cluster.
312 * It scan the list of local thread, and sets the THREAD_BLOCKED_GLOBAL bit for all
313 * threads, BUT the main thread (thread 0 in owner cluster), and the client thread
314 * identified by the <client_xp> argument. It request the relevant schedulers to acknowledge
315 * the blocking, using IPI if required, and returns only when all blockable threads
316 * in cluster are actually blocked.
317 * The threads are not detached from the scheduler, and not detached from the local process.
318 *********************************************************************************************
319 * @ process     : pointer on the target process descriptor.
320 * @ client_xp   : extended pointer on the client thread that should not be blocked.
321 ********************************************************************************************/
322void process_block_threads( process_t * process,
323                            xptr_t      client_xp );
324
325/*********************************************************************************************
326 * This function marks for deletion all threads for a given <process> in the local cluster.
327 * It scan the list of local thread, and sets the THREAD_FLAG_REQ_DELETE bit for all
328 * threads, BUT the main thread (thread 0 in owner cluster), and the client thread
329 * identified by the <client_xp> argument.
330 * The actual deletion will be done by the scheduler at the next scheduling point.
331 *********************************************************************************************
332 * @ process     : pointer on the process descriptor.
333 * @ client_xp   : extended pointer on the client thread that should not be marked.
334 ********************************************************************************************/
335void process_delete_threads( process_t * process,
336                            xptr_t       client_xp );
337
338/*********************************************************************************************
339 * This function unblocks all threads of a given user process in a given cluster.
340 *********************************************************************************************
341 * @ process     : pointer on the process descriptor.
342 ********************************************************************************************/
343void process_unblock_threads( process_t * process );
344
345/*********************************************************************************************
346 * This function returns a pointer on the local copy of a process identified by its PID.
347 * If this local copy does not exist yet, it is dynamically created, from the reference
348 * process descriptor, registered in the global copies_list, and registered in the local_list.
349 * This function is used by the thread_user_create() function.
350 *********************************************************************************************
351 * @ pid     : searched process identifier.
352 * @ returns pointer on the local process descriptor if success / returns NULL if failure.
353 ********************************************************************************************/
354process_t * process_get_local_copy( pid_t pid );
355
356/*********************************************************************************************
357 * This function returns the parent process identifier for a remote process descriptor
358 * identified by an extended pointer.
359 *********************************************************************************************
360 * @ process_xp   : extended pointer on remote process descriptor.
361 * @ returns parent process dentifier.
362 ********************************************************************************************/
363pid_t process_get_ppid( xptr_t process_xp );
364
365/*********************************************************************************************
366 * This function implements the "exec" system call, and is called by the sys_exec() function.
367 * The "new" process keep the "old" process PID and PPID, all open files, and env variables,
368 * the vfs_root and vfs_cwd, but build a brand new memory image (new VMM from the new .elf).
369 * It actually creates a "new" reference process descriptor, and copies all relevant
370 * information from the "old" process descriptor to the "new" process descriptor.
371 * It completes the "new" process descriptor, from information found in the <exec_info>
372 * structure (defined in the process.h file), that must be built by the caller.
373 * It creates and initializes the associated main thread. It finally destroys all copies
374 * of the "old" process in all clusters, and destroys all old associated threads.
375 * It is executed in the local cluster, that becomes both the "owner" and the "reference"
376 * cluster for the "new" process.
377 *********************************************************************************************
378 * @ exec_info   : [in]  pointer on the exec_info structure.
379 * @ return 0 if success / return non-zero if error.
380 ********************************************************************************************/
381error_t process_make_exec( exec_info_t * exec_info );
382
383/*********************************************************************************************
384 * This function implements the "fork" system call, and is called by the sys_fork() function,
385 * likely throuch the RPC_PROCESS_MAKE_FORK.
386 * It allocates memory and initializes a new "child" process descriptor, and the associated
387 * "child" thread descriptor in local cluster. It involves up to three different clusters :
388 * - the child (local) cluster can be any cluster selected by the sys_fork function.
389 * - the parent cluster must be the reference cluster for the parent process.
390 * - the client cluster containing the thread requesting the fork can be any cluster.
391 * The new "child" process descriptor is initialised from informations found in the "parent"
392 * reference process descriptor, containing the complete process description.
393 * The new "child" thread descriptor is initialised from informations found in the "parent"
394 * thread descriptor.
395 *********************************************************************************************
396 * @ parent_process_xp  : extended pointer on the reference parent process.
397 * @ parent_thread_xp   : extended pointer on the parent thread requesting the fork.
398 * @ child_pid          : [out] child process identifier.
399 * @ child_thread_ptr   : [out] local pointer on child thread in target cluster.
400 * @ return 0 if success / return non-zero if error.
401 ********************************************************************************************/
402error_t process_make_fork(  xptr_t             parent_process_xp,
403                            xptr_t             parent_thread_xp,
404                            pid_t            * child_pid, 
405                            struct thread_s ** child_thread_ptr );
406
407
408/********************   File Management Operations   ****************************************/
409
410/*********************************************************************************************
411 * This function initializes all entries of the local fd_array as empty.
412 *********************************************************************************************
413 * @ process  : pointer on the local process descriptor.
414 ********************************************************************************************/
415void process_fd_init( process_t * process );
416
417/*********************************************************************************************
418 * This function uses as many remote accesses as required, to reset an entry in fd_array[],
419 * in all clusters containing a copy. The entry is identified by the <fdid> argument.
420 * This function must be executed by a thread running reference cluster, that contains
421 * the complete list of process descriptors copies.
422 *********************************************************************************************
423 * @ process  : pointer on the local process descriptor.
424 * @ fdid     : file descriptor index in the fd_array.
425 ********************************************************************************************/
426void process_fd_remove( process_t * process,
427                        uint32_t    fdid );
428
429/*********************************************************************************************
430 * This function returns an extended pointer on a file descriptor identified by its index
431 * in fd_array. It can be called by any thread running in any cluster.
432 * It accesses first the local process descriptor. In case of local miss, it uses remote
433 * access to access the reference process descriptor.
434 * It updates the local fd_array when the file descriptor exists in reference cluster.
435 * The file descriptor refcount is not incremented.
436 *********************************************************************************************
437 * @ process  : pointer on the local process descriptor.
438 * @ fdid     : file descriptor index in the fd_array.
439 * @ return extended pointer on file descriptor if success / return XPTR_NULL if not found.
440 ********************************************************************************************/
441xptr_t process_fd_get_xptr( process_t * process,
442                            uint32_t    fdid );
443
444/*********************************************************************************************
445 * This function checks the number of open files for a given process.
446 * It can be called by any thread in any cluster, because it uses portable remote access
447 * primitives to access the reference process descriptor.
448 *********************************************************************************************
449 * @ returns true if file descriptor array full.
450 ********************************************************************************************/
451bool_t process_fd_array_full();
452
453/*********************************************************************************************
454 * This function allocates a free slot in the fd_array of the reference process,
455 * register the <file_xp> argument in the allocated slot, and return the slot index.
456 * It can be called by any thread in any cluster, because it uses portable remote access
457 * primitives to access the reference process descriptor.
458 *********************************************************************************************
459 * @ file_xp  : extended pointer on the file descriptor to be registered.
460 * @ fdid     : [out] buffer for fd_array slot index.
461 * @ return 0 if success / return EMFILE if array full.
462 ********************************************************************************************/
463error_t process_fd_register( process_t * process,
464                             xptr_t      file_xp,
465                             uint32_t  * fdid );
466
467/*********************************************************************************************
468 * This function copies all non-zero entries (other than the three first stdin/stdout/stderr)
469 * from a remote <src_xp> fd_array, embedded in a process descriptor, to another remote
470 * <dst_xp> fd_array, embedded in another process descriptor.
471 * The calling thread can be running in any cluster.
472 * It takes the remote lock protecting the <src_xp> fd_array during the copy.
473 * For each involved file descriptor, the refcount is incremented.
474 *********************************************************************************************
475 * @ dst_xp   : extended pointer on the destination fd_array_t.
476 * @ src_xp   : extended pointer on the source fd_array_t.
477 ********************************************************************************************/
478void process_fd_remote_copy( xptr_t dst_xp,
479                             xptr_t src_xp );
480
481
482
483/********************   Thread Related Operations   *****************************************/
484
485/*********************************************************************************************
486 * This function registers a new thread in the local process descriptor.
487 * It checks that there is an available slot in the local th_tbl[] array,
488 * allocates a new LTID, and registers the new thread in the th_tbl[].
489 * It takes the lock protecting exclusive access to the th_tbl[].
490 *********************************************************************************************
491 * @ process  : pointer on the local process descriptor.
492 * @ thread   : pointer on new thread to be registered.
493 * @ trdid    : [out] address of buffer for allocated trdid.
494 * @ returns 0 if success / returns non zero if no slot available.
495 ********************************************************************************************/
496error_t process_register_thread( process_t       * process,
497                                 struct thread_s * thread,
498                                 trdid_t         * trdid );
499
500/*********************************************************************************************
501 * This function removes a thread registration from the local process descriptor.
502 * It takes the lock protecting exclusive access to the th_tbl[].
503 *********************************************************************************************
504 * @ thread   : local pointer on thread to be removed.
505 * @ return true if the removed thread was the last registered thread.
506 ********************************************************************************************/
507bool_t process_remove_thread( struct thread_s * thread );
508
509
510/***************   Terminals related operations  ********************************************/
511
512/*********************************************************************************************
513 * This function scan the set of user TXT terminals to find a free terminal
514 * (the list of attached processes is empty for a free TXT terminal).
515 * It is called only by the process_reference_init() function when creating a KSH process.
516 * It makes a kernel panic if no free TXT terminal is found.
517 * The allocated TXT terminal is only released if the KSH process is deleted,
518 * which is a rare and abnormal event.
519 *********************************************************************************************
520 * @ return TXT terminal index if succes / kernel panic if no terminal found.
521 ********************************************************************************************/
522uint32_t process_txt_alloc();
523
524/*********************************************************************************************
525 * This function attach a process, identified by the <process> argument to a TXT terminal,
526 * identified by the <txt_id> channel index argument.
527 * The process descriptor identified by the <process> argument must be in the owner cluster. 
528 * It insert the process descriptor in the xlist rooted in the TXT_RX device.
529 * It is called by the process_reference_init() function.
530 *********************************************************************************************
531 * @ process  : local pointer on process descriptor.
532 * @ txt_id   : TXT channel index.
533 ********************************************************************************************/
534void process_txt_attach( process_t * process,
535                         uint32_t    txt_id );
536
537/*********************************************************************************************
538 * This function detach a process, identified by the <process_xp> argument,
539 * from the list of process attached to a given TXT terminal. It transfer the TXT ownership
540 * to another process, if the detached process is the TXT owner.
541 * The process descriptor identified by the <process_xp> argument must be in the owner
542 * cluster, but the calling thread can be running in any cluster.
543 *********************************************************************************************
544 * @ process_xp  : extended pointer on process descriptor.
545 ********************************************************************************************/
546void process_txt_detach( xptr_t  process_xp );                     
547
548/*********************************************************************************************
549 * This function gives to a process identified by the <owner_xp> argument, and attached
550 * to terminal TXT[i] the exclusive ownership of the TXT_RX[i] terminal.
551 * The process descriptor must be in the process owner cluster.
552 *********************************************************************************************
553 * @ owner_xp  : extended pointer on process descriptor in owner cluster.
554 ********************************************************************************************/
555void process_txt_set_ownership( xptr_t owner_xp );
556
557/*********************************************************************************************
558 * When the process dentified by the <owner_xp> argument has the exclusive ownership of
559 * the TXT_RX terminal, this function transfer this ownership to another attached process.
560 * The process descriptor must be the process owner.
561 * This function does nothing if the process identified by the <process_xp> is not
562 * the TXT owner.
563 * - If the current owner is not the KSH process, the new owner is the KSH process.
564 * - If the current owner is the KSH process, the new owner is another attached process.
565 * - If there is no other attached process, the TXT has no more defined owner.
566 *********************************************************************************************
567 * @ owner_xp  : extended pointer on process descriptor in owner cluster.
568 ********************************************************************************************/
569void process_txt_transfer_ownership( xptr_t owner_xp );
570
571/*********************************************************************************************
572 * This function returns the TXT owner process (foreground process)
573 * for a given TXT terminal identified by its <channel> index.
574 *********************************************************************************************
575 * @ channel  : TXT terminal channel.
576 * @ return extentded pointer on TXT owner process in owner cluster.
577 ********************************************************************************************/
578xptr_t process_txt_get_owner( uint32_t channel );
579
580/*********************************************************************************************
581 * This debug function diplays on the kernel terminal the list of processes attached
582 * to a given terminal identified by the <txt_id> argument.
583 *********************************************************************************************
584 * @ txt_id  : TXT terminal channel.
585 ********************************************************************************************/
586void process_txt_display( uint32_t txt_id );
587
588
589#endif  /* _PROCESS_H_ */
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