[PATCH] rcu file: use atomic primitives
[linux-2.6.git] / kernel / rcutorture.c
1 /*
2  * Read-Copy Update /proc-based torture test facility
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License as published by
6  * the Free Software Foundation; either version 2 of the License, or
7  * (at your option) any later version.
8  *
9  * This program is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12  * GNU General Public License for more details.
13  *
14  * You should have received a copy of the GNU General Public License
15  * along with this program; if not, write to the Free Software
16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17  *
18  * Copyright (C) IBM Corporation, 2005
19  *
20  * Authors: Paul E. McKenney <paulmck@us.ibm.com>
21  *
22  * See also:  Documentation/RCU/torture.txt
23  */
24 #include <linux/types.h>
25 #include <linux/kernel.h>
26 #include <linux/init.h>
27 #include <linux/module.h>
28 #include <linux/kthread.h>
29 #include <linux/err.h>
30 #include <linux/spinlock.h>
31 #include <linux/smp.h>
32 #include <linux/rcupdate.h>
33 #include <linux/interrupt.h>
34 #include <linux/sched.h>
35 #include <asm/atomic.h>
36 #include <linux/bitops.h>
37 #include <linux/module.h>
38 #include <linux/completion.h>
39 #include <linux/moduleparam.h>
40 #include <linux/percpu.h>
41 #include <linux/notifier.h>
42 #include <linux/cpu.h>
43 #include <linux/random.h>
44 #include <linux/delay.h>
45 #include <linux/byteorder/swabb.h>
46 #include <linux/stat.h>
47
48 MODULE_LICENSE("GPL");
49
50 static int nreaders = -1;       /* # reader threads, defaults to 4*ncpus */
51 static int stat_interval = 0;   /* Interval between stats, in seconds. */
52                                 /*  Defaults to "only at end of test". */
53 static int verbose = 0;         /* Print more debug info. */
54
55 MODULE_PARM(nreaders, "i");
56 MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
57 MODULE_PARM(stat_interval, "i");
58 MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
59 MODULE_PARM(verbose, "i");
60 MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
61 #define TORTURE_FLAG "rcutorture: "
62 #define PRINTK_STRING(s) \
63         do { printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
64 #define VERBOSE_PRINTK_STRING(s) \
65         do { if (verbose) printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
66 #define VERBOSE_PRINTK_ERRSTRING(s) \
67         do { if (verbose) printk(KERN_ALERT TORTURE_FLAG "!!! " s "\n"); } while (0)
68
69 static char printk_buf[4096];
70
71 static int nrealreaders;
72 static struct task_struct *writer_task;
73 static struct task_struct **reader_tasks;
74 static struct task_struct *stats_task;
75
76 #define RCU_TORTURE_PIPE_LEN 10
77
78 struct rcu_torture {
79         struct rcu_head rtort_rcu;
80         int rtort_pipe_count;
81         struct list_head rtort_free;
82         int rtort_mbtest;
83 };
84
85 static int fullstop = 0;        /* stop generating callbacks at test end. */
86 static LIST_HEAD(rcu_torture_freelist);
87 static struct rcu_torture *rcu_torture_current = NULL;
88 static long rcu_torture_current_version = 0;
89 static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
90 static DEFINE_SPINLOCK(rcu_torture_lock);
91 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
92         { 0 };
93 static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
94         { 0 };
95 static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
96 atomic_t n_rcu_torture_alloc;
97 atomic_t n_rcu_torture_alloc_fail;
98 atomic_t n_rcu_torture_free;
99 atomic_t n_rcu_torture_mberror;
100 atomic_t n_rcu_torture_error;
101
102 /*
103  * Allocate an element from the rcu_tortures pool.
104  */
105 static struct rcu_torture *
106 rcu_torture_alloc(void)
107 {
108         struct list_head *p;
109
110         spin_lock(&rcu_torture_lock);
111         if (list_empty(&rcu_torture_freelist)) {
112                 atomic_inc(&n_rcu_torture_alloc_fail);
113                 spin_unlock(&rcu_torture_lock);
114                 return NULL;
115         }
116         atomic_inc(&n_rcu_torture_alloc);
117         p = rcu_torture_freelist.next;
118         list_del_init(p);
119         spin_unlock(&rcu_torture_lock);
120         return container_of(p, struct rcu_torture, rtort_free);
121 }
122
123 /*
124  * Free an element to the rcu_tortures pool.
125  */
126 static void
127 rcu_torture_free(struct rcu_torture *p)
128 {
129         atomic_inc(&n_rcu_torture_free);
130         spin_lock(&rcu_torture_lock);
131         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
132         spin_unlock(&rcu_torture_lock);
133 }
134
135 static void
136 rcu_torture_cb(struct rcu_head *p)
137 {
138         int i;
139         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
140
141         if (fullstop) {
142                 /* Test is ending, just drop callbacks on the floor. */
143                 /* The next initialization will pick up the pieces. */
144                 return;
145         }
146         i = rp->rtort_pipe_count;
147         if (i > RCU_TORTURE_PIPE_LEN)
148                 i = RCU_TORTURE_PIPE_LEN;
149         atomic_inc(&rcu_torture_wcount[i]);
150         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
151                 rp->rtort_mbtest = 0;
152                 rcu_torture_free(rp);
153         } else
154                 call_rcu(p, rcu_torture_cb);
155 }
156
157 struct rcu_random_state {
158         unsigned long rrs_state;
159         unsigned long rrs_count;
160 };
161
162 #define RCU_RANDOM_MULT 39916801  /* prime */
163 #define RCU_RANDOM_ADD  479001701 /* prime */
164 #define RCU_RANDOM_REFRESH 10000
165
166 #define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
167
168 /*
169  * Crude but fast random-number generator.  Uses a linear congruential
170  * generator, with occasional help from get_random_bytes().
171  */
172 static long
173 rcu_random(struct rcu_random_state *rrsp)
174 {
175         long refresh;
176
177         if (--rrsp->rrs_count < 0) {
178                 get_random_bytes(&refresh, sizeof(refresh));
179                 rrsp->rrs_state += refresh;
180                 rrsp->rrs_count = RCU_RANDOM_REFRESH;
181         }
182         rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
183         return swahw32(rrsp->rrs_state);
184 }
185
186 /*
187  * RCU torture writer kthread.  Repeatedly substitutes a new structure
188  * for that pointed to by rcu_torture_current, freeing the old structure
189  * after a series of grace periods (the "pipeline").
190  */
191 static int
192 rcu_torture_writer(void *arg)
193 {
194         int i;
195         long oldbatch = rcu_batches_completed();
196         struct rcu_torture *rp;
197         struct rcu_torture *old_rp;
198         static DEFINE_RCU_RANDOM(rand);
199
200         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
201         set_user_nice(current, 19);
202
203         do {
204                 schedule_timeout_uninterruptible(1);
205                 if (rcu_batches_completed() == oldbatch)
206                         continue;
207                 if ((rp = rcu_torture_alloc()) == NULL)
208                         continue;
209                 rp->rtort_pipe_count = 0;
210                 udelay(rcu_random(&rand) & 0x3ff);
211                 old_rp = rcu_torture_current;
212                 rp->rtort_mbtest = 1;
213                 rcu_assign_pointer(rcu_torture_current, rp);
214                 smp_wmb();
215                 if (old_rp != NULL) {
216                         i = old_rp->rtort_pipe_count;
217                         if (i > RCU_TORTURE_PIPE_LEN)
218                                 i = RCU_TORTURE_PIPE_LEN;
219                         atomic_inc(&rcu_torture_wcount[i]);
220                         old_rp->rtort_pipe_count++;
221                         call_rcu(&old_rp->rtort_rcu, rcu_torture_cb);
222                 }
223                 rcu_torture_current_version++;
224                 oldbatch = rcu_batches_completed();
225         } while (!kthread_should_stop() && !fullstop);
226         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
227         while (!kthread_should_stop())
228                 schedule_timeout_uninterruptible(1);
229         return 0;
230 }
231
232 /*
233  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
234  * incrementing the corresponding element of the pipeline array.  The
235  * counter in the element should never be greater than 1, otherwise, the
236  * RCU implementation is broken.
237  */
238 static int
239 rcu_torture_reader(void *arg)
240 {
241         int completed;
242         DEFINE_RCU_RANDOM(rand);
243         struct rcu_torture *p;
244         int pipe_count;
245
246         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
247         set_user_nice(current, 19);
248
249         do {
250                 rcu_read_lock();
251                 completed = rcu_batches_completed();
252                 p = rcu_dereference(rcu_torture_current);
253                 if (p == NULL) {
254                         /* Wait for rcu_torture_writer to get underway */
255                         rcu_read_unlock();
256                         schedule_timeout_interruptible(HZ);
257                         continue;
258                 }
259                 if (p->rtort_mbtest == 0)
260                         atomic_inc(&n_rcu_torture_mberror);
261                 udelay(rcu_random(&rand) & 0x7f);
262                 preempt_disable();
263                 pipe_count = p->rtort_pipe_count;
264                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
265                         /* Should not happen, but... */
266                         pipe_count = RCU_TORTURE_PIPE_LEN;
267                 }
268                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
269                 completed = rcu_batches_completed() - completed;
270                 if (completed > RCU_TORTURE_PIPE_LEN) {
271                         /* Should not happen, but... */
272                         completed = RCU_TORTURE_PIPE_LEN;
273                 }
274                 ++__get_cpu_var(rcu_torture_batch)[completed];
275                 preempt_enable();
276                 rcu_read_unlock();
277                 schedule();
278         } while (!kthread_should_stop() && !fullstop);
279         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
280         while (!kthread_should_stop())
281                 schedule_timeout_uninterruptible(1);
282         return 0;
283 }
284
285 /*
286  * Create an RCU-torture statistics message in the specified buffer.
287  */
288 static int
289 rcu_torture_printk(char *page)
290 {
291         int cnt = 0;
292         int cpu;
293         int i;
294         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
295         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
296
297         for_each_cpu(cpu) {
298                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
299                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
300                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
301                 }
302         }
303         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
304                 if (pipesummary[i] != 0)
305                         break;
306         }
307         cnt += sprintf(&page[cnt], "rcutorture: ");
308         cnt += sprintf(&page[cnt],
309                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d "
310                        "rtmbe: %d",
311                        rcu_torture_current,
312                        rcu_torture_current_version,
313                        list_empty(&rcu_torture_freelist),
314                        atomic_read(&n_rcu_torture_alloc),
315                        atomic_read(&n_rcu_torture_alloc_fail),
316                        atomic_read(&n_rcu_torture_free),
317                        atomic_read(&n_rcu_torture_mberror));
318         if (atomic_read(&n_rcu_torture_mberror) != 0)
319                 cnt += sprintf(&page[cnt], " !!!");
320         cnt += sprintf(&page[cnt], "\nrcutorture: ");
321         if (i > 1) {
322                 cnt += sprintf(&page[cnt], "!!! ");
323                 atomic_inc(&n_rcu_torture_error);
324         }
325         cnt += sprintf(&page[cnt], "Reader Pipe: ");
326         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
327                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
328         cnt += sprintf(&page[cnt], "\nrcutorture: ");
329         cnt += sprintf(&page[cnt], "Reader Batch: ");
330         for (i = 0; i < RCU_TORTURE_PIPE_LEN; i++)
331                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
332         cnt += sprintf(&page[cnt], "\nrcutorture: ");
333         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
334         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
335                 cnt += sprintf(&page[cnt], " %d",
336                                atomic_read(&rcu_torture_wcount[i]));
337         }
338         cnt += sprintf(&page[cnt], "\n");
339         return cnt;
340 }
341
342 /*
343  * Print torture statistics.  Caller must ensure that there is only
344  * one call to this function at a given time!!!  This is normally
345  * accomplished by relying on the module system to only have one copy
346  * of the module loaded, and then by giving the rcu_torture_stats
347  * kthread full control (or the init/cleanup functions when rcu_torture_stats
348  * thread is not running).
349  */
350 static void
351 rcu_torture_stats_print(void)
352 {
353         int cnt;
354
355         cnt = rcu_torture_printk(printk_buf);
356         printk(KERN_ALERT "%s", printk_buf);
357 }
358
359 /*
360  * Periodically prints torture statistics, if periodic statistics printing
361  * was specified via the stat_interval module parameter.
362  *
363  * No need to worry about fullstop here, since this one doesn't reference
364  * volatile state or register callbacks.
365  */
366 static int
367 rcu_torture_stats(void *arg)
368 {
369         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
370         do {
371                 schedule_timeout_interruptible(stat_interval * HZ);
372                 rcu_torture_stats_print();
373         } while (!kthread_should_stop());
374         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
375         return 0;
376 }
377
378 static void
379 rcu_torture_cleanup(void)
380 {
381         int i;
382
383         fullstop = 1;
384         if (writer_task != NULL) {
385                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
386                 kthread_stop(writer_task);
387         }
388         writer_task = NULL;
389
390         if (reader_tasks != NULL) {
391                 for (i = 0; i < nrealreaders; i++) {
392                         if (reader_tasks[i] != NULL) {
393                                 VERBOSE_PRINTK_STRING(
394                                         "Stopping rcu_torture_reader task");
395                                 kthread_stop(reader_tasks[i]);
396                         }
397                         reader_tasks[i] = NULL;
398                 }
399                 kfree(reader_tasks);
400                 reader_tasks = NULL;
401         }
402         rcu_torture_current = NULL;
403
404         if (stats_task != NULL) {
405                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
406                 kthread_stop(stats_task);
407         }
408         stats_task = NULL;
409
410         /* Wait for all RCU callbacks to fire.  */
411         rcu_barrier();
412
413         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
414         printk(KERN_ALERT TORTURE_FLAG
415                "--- End of test: %s\n",
416                atomic_read(&n_rcu_torture_error) == 0 ? "SUCCESS" : "FAILURE");
417 }
418
419 static int
420 rcu_torture_init(void)
421 {
422         int i;
423         int cpu;
424         int firsterr = 0;
425
426         /* Process args and tell the world that the torturer is on the job. */
427
428         if (nreaders >= 0)
429                 nrealreaders = nreaders;
430         else
431                 nrealreaders = 2 * num_online_cpus();
432         printk(KERN_ALERT TORTURE_FLAG
433                "--- Start of test: nreaders=%d stat_interval=%d verbose=%d\n",
434                nrealreaders, stat_interval, verbose);
435         fullstop = 0;
436
437         /* Set up the freelist. */
438
439         INIT_LIST_HEAD(&rcu_torture_freelist);
440         for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
441                 rcu_tortures[i].rtort_mbtest = 0;
442                 list_add_tail(&rcu_tortures[i].rtort_free,
443                               &rcu_torture_freelist);
444         }
445
446         /* Initialize the statistics so that each run gets its own numbers. */
447
448         rcu_torture_current = NULL;
449         rcu_torture_current_version = 0;
450         atomic_set(&n_rcu_torture_alloc, 0);
451         atomic_set(&n_rcu_torture_alloc_fail, 0);
452         atomic_set(&n_rcu_torture_free, 0);
453         atomic_set(&n_rcu_torture_mberror, 0);
454         atomic_set(&n_rcu_torture_error, 0);
455         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
456                 atomic_set(&rcu_torture_wcount[i], 0);
457         for_each_cpu(cpu) {
458                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
459                         per_cpu(rcu_torture_count, cpu)[i] = 0;
460                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
461                 }
462         }
463
464         /* Start up the kthreads. */
465
466         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
467         writer_task = kthread_run(rcu_torture_writer, NULL,
468                                   "rcu_torture_writer");
469         if (IS_ERR(writer_task)) {
470                 firsterr = PTR_ERR(writer_task);
471                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
472                 writer_task = NULL;
473                 goto unwind;
474         }
475         reader_tasks = kmalloc(nrealreaders * sizeof(reader_tasks[0]),
476                                GFP_KERNEL);
477         if (reader_tasks == NULL) {
478                 VERBOSE_PRINTK_ERRSTRING("out of memory");
479                 firsterr = -ENOMEM;
480                 goto unwind;
481         }
482         for (i = 0; i < nrealreaders; i++) {
483                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
484                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
485                                               "rcu_torture_reader");
486                 if (IS_ERR(reader_tasks[i])) {
487                         firsterr = PTR_ERR(reader_tasks[i]);
488                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
489                         reader_tasks[i] = NULL;
490                         goto unwind;
491                 }
492         }
493         if (stat_interval > 0) {
494                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
495                 stats_task = kthread_run(rcu_torture_stats, NULL,
496                                         "rcu_torture_stats");
497                 if (IS_ERR(stats_task)) {
498                         firsterr = PTR_ERR(stats_task);
499                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
500                         stats_task = NULL;
501                         goto unwind;
502                 }
503         }
504         return 0;
505
506 unwind:
507         rcu_torture_cleanup();
508         return firsterr;
509 }
510
511 module_init(rcu_torture_init);
512 module_exit(rcu_torture_cleanup);