[PATCH] RCU torture-testing kernel module
[linux-3.10.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/rcuref.h>
43 #include <linux/cpu.h>
44 #include <linux/random.h>
45 #include <linux/delay.h>
46 #include <linux/byteorder/swabb.h>
47 #include <linux/stat.h>
48
49 MODULE_LICENSE("GPL");
50
51 static int nreaders = -1;       /* # reader threads, defaults to 4*ncpus */
52 static int stat_interval = 0;   /* Interval between stats, in seconds. */
53                                 /*  Defaults to "only at end of test". */
54 static int verbose = 0;         /* Print more debug info. */
55
56 MODULE_PARM(nreaders, "i");
57 MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
58 MODULE_PARM(stat_interval, "i");
59 MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
60 MODULE_PARM(verbose, "i");
61 MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
62 #define TORTURE_FLAG "rcutorture: "
63 #define PRINTK_STRING(s) \
64         do { printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
65 #define VERBOSE_PRINTK_STRING(s) \
66         do { if (verbose) printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
67 #define VERBOSE_PRINTK_ERRSTRING(s) \
68         do { if (verbose) printk(KERN_ALERT TORTURE_FLAG "!!! " s "\n"); } while (0)
69
70 static char printk_buf[4096];
71
72 static int nrealreaders;
73 static struct task_struct *writer_task;
74 static struct task_struct **reader_tasks;
75 static struct task_struct *stats_task;
76
77 #define RCU_TORTURE_PIPE_LEN 10
78
79 struct rcu_torture {
80         struct rcu_head rtort_rcu;
81         int rtort_pipe_count;
82         struct list_head rtort_free;
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
100 /*
101  * Allocate an element from the rcu_tortures pool.
102  */
103 struct rcu_torture *
104 rcu_torture_alloc(void)
105 {
106         struct list_head *p;
107
108         spin_lock(&rcu_torture_lock);
109         if (list_empty(&rcu_torture_freelist)) {
110                 atomic_inc(&n_rcu_torture_alloc_fail);
111                 spin_unlock(&rcu_torture_lock);
112                 return NULL;
113         }
114         atomic_inc(&n_rcu_torture_alloc);
115         p = rcu_torture_freelist.next;
116         list_del_init(p);
117         spin_unlock(&rcu_torture_lock);
118         return container_of(p, struct rcu_torture, rtort_free);
119 }
120
121 /*
122  * Free an element to the rcu_tortures pool.
123  */
124 static void
125 rcu_torture_free(struct rcu_torture *p)
126 {
127         atomic_inc(&n_rcu_torture_free);
128         spin_lock(&rcu_torture_lock);
129         list_add_tail(&p->rtort_free, &rcu_torture_freelist);
130         spin_unlock(&rcu_torture_lock);
131 }
132
133 static void
134 rcu_torture_cb(struct rcu_head *p)
135 {
136         int i;
137         struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
138
139         if (fullstop) {
140                 /* Test is ending, just drop callbacks on the floor. */
141                 /* The next initialization will pick up the pieces. */
142                 return;
143         }
144         i = rp->rtort_pipe_count;
145         if (i > RCU_TORTURE_PIPE_LEN)
146                 i = RCU_TORTURE_PIPE_LEN;
147         atomic_inc(&rcu_torture_wcount[i]);
148         if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN)
149                 rcu_torture_free(rp);
150         else
151                 call_rcu(p, rcu_torture_cb);
152 }
153
154 struct rcu_random_state {
155         unsigned long rrs_state;
156         unsigned long rrs_count;
157 };
158
159 #define RCU_RANDOM_MULT 39916801  /* prime */
160 #define RCU_RANDOM_ADD  479001701 /* prime */
161 #define RCU_RANDOM_REFRESH 10000
162
163 #define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
164
165 /*
166  * Crude but fast random-number generator.  Uses a linear congruential
167  * generator, with occasional help from get_random_bytes().
168  */
169 static long
170 rcu_random(struct rcu_random_state *rrsp)
171 {
172         long refresh;
173
174         if (--rrsp->rrs_count < 0) {
175                 get_random_bytes(&refresh, sizeof(refresh));
176                 rrsp->rrs_state += refresh;
177                 rrsp->rrs_count = RCU_RANDOM_REFRESH;
178         }
179         rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
180         return swahw32(rrsp->rrs_state);
181 }
182
183 /*
184  * RCU torture writer kthread.  Repeatedly substitutes a new structure
185  * for that pointed to by rcu_torture_current, freeing the old structure
186  * after a series of grace periods (the "pipeline").
187  */
188 static int
189 rcu_torture_writer(void *arg)
190 {
191         int i;
192         long oldbatch = rcu_batches_completed();
193         struct rcu_torture *rp;
194         struct rcu_torture *old_rp;
195         static DEFINE_RCU_RANDOM(rand);
196
197         VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
198         do {
199                 schedule_timeout_uninterruptible(1);
200                 if (rcu_batches_completed() == oldbatch)
201                         continue;
202                 if ((rp = rcu_torture_alloc()) == NULL)
203                         continue;
204                 rp->rtort_pipe_count = 0;
205                 udelay(rcu_random(&rand) & 0x3ff);
206                 old_rp = rcu_torture_current;
207                 rcu_assign_pointer(rcu_torture_current, rp);
208                 smp_wmb();
209                 if (old_rp != NULL) {
210                         i = old_rp->rtort_pipe_count;
211                         if (i > RCU_TORTURE_PIPE_LEN)
212                                 i = RCU_TORTURE_PIPE_LEN;
213                         atomic_inc(&rcu_torture_wcount[i]);
214                         old_rp->rtort_pipe_count++;
215                         call_rcu(&old_rp->rtort_rcu, rcu_torture_cb);
216                 }
217                 rcu_torture_current_version++;
218                 oldbatch = rcu_batches_completed();
219         } while (!kthread_should_stop() && !fullstop);
220         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
221         while (!kthread_should_stop())
222                 schedule_timeout_uninterruptible(1);
223         return 0;
224 }
225
226 /*
227  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
228  * incrementing the corresponding element of the pipeline array.  The
229  * counter in the element should never be greater than 1, otherwise, the
230  * RCU implementation is broken.
231  */
232 static int
233 rcu_torture_reader(void *arg)
234 {
235         int completed;
236         DEFINE_RCU_RANDOM(rand);
237         struct rcu_torture *p;
238         int pipe_count;
239
240         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
241         do {
242                 rcu_read_lock();
243                 completed = rcu_batches_completed();
244                 p = rcu_dereference(rcu_torture_current);
245                 if (p == NULL) {
246                         /* Wait for rcu_torture_writer to get underway */
247                         rcu_read_unlock();
248                         schedule_timeout_interruptible(HZ);
249                         continue;
250                 }
251                 udelay(rcu_random(&rand) & 0x7f);
252                 preempt_disable();
253                 pipe_count = p->rtort_pipe_count;
254                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
255                         /* Should not happen, but... */
256                         pipe_count = RCU_TORTURE_PIPE_LEN;
257                 }
258                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
259                 completed = rcu_batches_completed() - completed;
260                 if (completed > RCU_TORTURE_PIPE_LEN) {
261                         /* Should not happen, but... */
262                         completed = RCU_TORTURE_PIPE_LEN;
263                 }
264                 ++__get_cpu_var(rcu_torture_batch)[completed];
265                 preempt_enable();
266                 rcu_read_unlock();
267                 schedule();
268         } while (!kthread_should_stop() && !fullstop);
269         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
270         while (!kthread_should_stop())
271                 schedule_timeout_uninterruptible(1);
272         return 0;
273 }
274
275 /*
276  * Create an RCU-torture statistics message in the specified buffer.
277  */
278 static int
279 rcu_torture_printk(char *page)
280 {
281         int cnt = 0;
282         int cpu;
283         int i;
284         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
285         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
286
287         for_each_cpu(cpu) {
288                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
289                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
290                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
291                 }
292         }
293         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
294                 if (pipesummary[i] != 0)
295                         break;
296         }
297         cnt += sprintf(&page[cnt], "rcutorture: ");
298         cnt += sprintf(&page[cnt],
299                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d",
300                        rcu_torture_current,
301                        rcu_torture_current_version,
302                        list_empty(&rcu_torture_freelist),
303                        atomic_read(&n_rcu_torture_alloc),
304                        atomic_read(&n_rcu_torture_alloc_fail),
305                        atomic_read(&n_rcu_torture_free));
306         cnt += sprintf(&page[cnt], "\nrcutorture: ");
307         if (i > 1)
308                 cnt += sprintf(&page[cnt], "!!! ");
309         cnt += sprintf(&page[cnt], "Reader Pipe: ");
310         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
311                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
312         cnt += sprintf(&page[cnt], "\nrcutorture: ");
313         cnt += sprintf(&page[cnt], "Reader Batch: ");
314         for (i = 0; i < RCU_TORTURE_PIPE_LEN; i++)
315                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
316         cnt += sprintf(&page[cnt], "\nrcutorture: ");
317         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
318         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
319                 cnt += sprintf(&page[cnt], " %d",
320                                atomic_read(&rcu_torture_wcount[i]));
321         }
322         cnt += sprintf(&page[cnt], "\n");
323         return cnt;
324 }
325
326 /*
327  * Print torture statistics.  Caller must ensure that there is only
328  * one call to this function at a given time!!!  This is normally
329  * accomplished by relying on the module system to only have one copy
330  * of the module loaded, and then by giving the rcu_torture_stats
331  * kthread full control (or the init/cleanup functions when rcu_torture_stats
332  * thread is not running).
333  */
334 static void
335 rcu_torture_stats_print(void)
336 {
337         int cnt;
338
339         cnt = rcu_torture_printk(printk_buf);
340         printk(KERN_ALERT "%s", printk_buf);
341 }
342
343 /*
344  * Periodically prints torture statistics, if periodic statistics printing
345  * was specified via the stat_interval module parameter.
346  *
347  * No need to worry about fullstop here, since this one doesn't reference
348  * volatile state or register callbacks.
349  */
350 static int
351 rcu_torture_stats(void *arg)
352 {
353         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
354         do {
355                 schedule_timeout_interruptible(stat_interval * HZ);
356                 rcu_torture_stats_print();
357         } while (!kthread_should_stop());
358         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
359         return 0;
360 }
361
362 static void
363 rcu_torture_cleanup(void)
364 {
365         int i;
366
367         fullstop = 1;
368         if (writer_task != NULL) {
369                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
370                 kthread_stop(writer_task);
371         }
372         writer_task = NULL;
373
374         if (reader_tasks != NULL) {
375                 for (i = 0; i < nrealreaders; i++) {
376                         if (reader_tasks[i] != NULL) {
377                                 VERBOSE_PRINTK_STRING(
378                                         "Stopping rcu_torture_reader task");
379                                 kthread_stop(reader_tasks[i]);
380                         }
381                         reader_tasks[i] = NULL;
382                 }
383                 kfree(reader_tasks);
384                 reader_tasks = NULL;
385         }
386         rcu_torture_current = NULL;
387
388         if (stats_task != NULL) {
389                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
390                 kthread_stop(stats_task);
391         }
392         stats_task = NULL;
393
394         /* Wait for all RCU callbacks to fire.  */
395
396         for (i = 0; i < RCU_TORTURE_PIPE_LEN; i++)
397                 synchronize_rcu();
398         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
399         PRINTK_STRING("--- End of test");
400 }
401
402 static int
403 rcu_torture_init(void)
404 {
405         int i;
406         int cpu;
407         int firsterr = 0;
408
409         /* Process args and tell the world that the torturer is on the job. */
410
411         if (nreaders >= 0)
412                 nrealreaders = nreaders;
413         else
414                 nrealreaders = 2 * num_online_cpus();
415         printk(KERN_ALERT TORTURE_FLAG
416                "--- Start of test: nreaders=%d stat_interval=%d verbose=%d\n",
417                nrealreaders, stat_interval, verbose);
418         fullstop = 0;
419
420         /* Set up the freelist. */
421
422         INIT_LIST_HEAD(&rcu_torture_freelist);
423         for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
424                 list_add_tail(&rcu_tortures[i].rtort_free,
425                               &rcu_torture_freelist);
426         }
427
428         /* Initialize the statistics so that each run gets its own numbers. */
429
430         rcu_torture_current = NULL;
431         rcu_torture_current_version = 0;
432         atomic_set(&n_rcu_torture_alloc, 0);
433         atomic_set(&n_rcu_torture_alloc_fail, 0);
434         atomic_set(&n_rcu_torture_free, 0);
435         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
436                 atomic_set(&rcu_torture_wcount[i], 0);
437         for_each_cpu(cpu) {
438                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
439                         per_cpu(rcu_torture_count, cpu)[i] = 0;
440                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
441                 }
442         }
443
444         /* Start up the kthreads. */
445
446         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
447         writer_task = kthread_run(rcu_torture_writer, NULL,
448                                   "rcu_torture_writer");
449         if (IS_ERR(writer_task)) {
450                 firsterr = PTR_ERR(writer_task);
451                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
452                 writer_task = NULL;
453                 goto unwind;
454         }
455         reader_tasks = kmalloc(nrealreaders * sizeof(reader_tasks[0]),
456                                GFP_KERNEL);
457         if (reader_tasks == NULL) {
458                 VERBOSE_PRINTK_ERRSTRING("out of memory");
459                 firsterr = -ENOMEM;
460                 goto unwind;
461         }
462         for (i = 0; i < nrealreaders; i++) {
463                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
464                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
465                                               "rcu_torture_reader");
466                 if (IS_ERR(reader_tasks[i])) {
467                         firsterr = PTR_ERR(reader_tasks[i]);
468                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
469                         reader_tasks[i] = NULL;
470                         goto unwind;
471                 }
472         }
473         if (stat_interval > 0) {
474                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
475                 stats_task = kthread_run(rcu_torture_stats, NULL,
476                                         "rcu_torture_stats");
477                 if (IS_ERR(stats_task)) {
478                         firsterr = PTR_ERR(stats_task);
479                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
480                         stats_task = NULL;
481                         goto unwind;
482                 }
483         }
484         return 0;
485
486 unwind:
487         rcu_torture_cleanup();
488         return firsterr;
489 }
490
491 module_init(rcu_torture_init);
492 module_exit(rcu_torture_cleanup);