[PATCH] rcutorture: renice to low priority
[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/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         set_user_nice(current, 19);
199
200         do {
201                 schedule_timeout_uninterruptible(1);
202                 if (rcu_batches_completed() == oldbatch)
203                         continue;
204                 if ((rp = rcu_torture_alloc()) == NULL)
205                         continue;
206                 rp->rtort_pipe_count = 0;
207                 udelay(rcu_random(&rand) & 0x3ff);
208                 old_rp = rcu_torture_current;
209                 rcu_assign_pointer(rcu_torture_current, rp);
210                 smp_wmb();
211                 if (old_rp != NULL) {
212                         i = old_rp->rtort_pipe_count;
213                         if (i > RCU_TORTURE_PIPE_LEN)
214                                 i = RCU_TORTURE_PIPE_LEN;
215                         atomic_inc(&rcu_torture_wcount[i]);
216                         old_rp->rtort_pipe_count++;
217                         call_rcu(&old_rp->rtort_rcu, rcu_torture_cb);
218                 }
219                 rcu_torture_current_version++;
220                 oldbatch = rcu_batches_completed();
221         } while (!kthread_should_stop() && !fullstop);
222         VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
223         while (!kthread_should_stop())
224                 schedule_timeout_uninterruptible(1);
225         return 0;
226 }
227
228 /*
229  * RCU torture reader kthread.  Repeatedly dereferences rcu_torture_current,
230  * incrementing the corresponding element of the pipeline array.  The
231  * counter in the element should never be greater than 1, otherwise, the
232  * RCU implementation is broken.
233  */
234 static int
235 rcu_torture_reader(void *arg)
236 {
237         int completed;
238         DEFINE_RCU_RANDOM(rand);
239         struct rcu_torture *p;
240         int pipe_count;
241
242         VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
243         set_user_nice(current, 19);
244
245         do {
246                 rcu_read_lock();
247                 completed = rcu_batches_completed();
248                 p = rcu_dereference(rcu_torture_current);
249                 if (p == NULL) {
250                         /* Wait for rcu_torture_writer to get underway */
251                         rcu_read_unlock();
252                         schedule_timeout_interruptible(HZ);
253                         continue;
254                 }
255                 udelay(rcu_random(&rand) & 0x7f);
256                 preempt_disable();
257                 pipe_count = p->rtort_pipe_count;
258                 if (pipe_count > RCU_TORTURE_PIPE_LEN) {
259                         /* Should not happen, but... */
260                         pipe_count = RCU_TORTURE_PIPE_LEN;
261                 }
262                 ++__get_cpu_var(rcu_torture_count)[pipe_count];
263                 completed = rcu_batches_completed() - completed;
264                 if (completed > RCU_TORTURE_PIPE_LEN) {
265                         /* Should not happen, but... */
266                         completed = RCU_TORTURE_PIPE_LEN;
267                 }
268                 ++__get_cpu_var(rcu_torture_batch)[completed];
269                 preempt_enable();
270                 rcu_read_unlock();
271                 schedule();
272         } while (!kthread_should_stop() && !fullstop);
273         VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
274         while (!kthread_should_stop())
275                 schedule_timeout_uninterruptible(1);
276         return 0;
277 }
278
279 /*
280  * Create an RCU-torture statistics message in the specified buffer.
281  */
282 static int
283 rcu_torture_printk(char *page)
284 {
285         int cnt = 0;
286         int cpu;
287         int i;
288         long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
289         long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
290
291         for_each_cpu(cpu) {
292                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
293                         pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
294                         batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
295                 }
296         }
297         for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
298                 if (pipesummary[i] != 0)
299                         break;
300         }
301         cnt += sprintf(&page[cnt], "rcutorture: ");
302         cnt += sprintf(&page[cnt],
303                        "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d",
304                        rcu_torture_current,
305                        rcu_torture_current_version,
306                        list_empty(&rcu_torture_freelist),
307                        atomic_read(&n_rcu_torture_alloc),
308                        atomic_read(&n_rcu_torture_alloc_fail),
309                        atomic_read(&n_rcu_torture_free));
310         cnt += sprintf(&page[cnt], "\nrcutorture: ");
311         if (i > 1)
312                 cnt += sprintf(&page[cnt], "!!! ");
313         cnt += sprintf(&page[cnt], "Reader Pipe: ");
314         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
315                 cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
316         cnt += sprintf(&page[cnt], "\nrcutorture: ");
317         cnt += sprintf(&page[cnt], "Reader Batch: ");
318         for (i = 0; i < RCU_TORTURE_PIPE_LEN; i++)
319                 cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
320         cnt += sprintf(&page[cnt], "\nrcutorture: ");
321         cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
322         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
323                 cnt += sprintf(&page[cnt], " %d",
324                                atomic_read(&rcu_torture_wcount[i]));
325         }
326         cnt += sprintf(&page[cnt], "\n");
327         return cnt;
328 }
329
330 /*
331  * Print torture statistics.  Caller must ensure that there is only
332  * one call to this function at a given time!!!  This is normally
333  * accomplished by relying on the module system to only have one copy
334  * of the module loaded, and then by giving the rcu_torture_stats
335  * kthread full control (or the init/cleanup functions when rcu_torture_stats
336  * thread is not running).
337  */
338 static void
339 rcu_torture_stats_print(void)
340 {
341         int cnt;
342
343         cnt = rcu_torture_printk(printk_buf);
344         printk(KERN_ALERT "%s", printk_buf);
345 }
346
347 /*
348  * Periodically prints torture statistics, if periodic statistics printing
349  * was specified via the stat_interval module parameter.
350  *
351  * No need to worry about fullstop here, since this one doesn't reference
352  * volatile state or register callbacks.
353  */
354 static int
355 rcu_torture_stats(void *arg)
356 {
357         VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
358         do {
359                 schedule_timeout_interruptible(stat_interval * HZ);
360                 rcu_torture_stats_print();
361         } while (!kthread_should_stop());
362         VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
363         return 0;
364 }
365
366 static void
367 rcu_torture_cleanup(void)
368 {
369         int i;
370
371         fullstop = 1;
372         if (writer_task != NULL) {
373                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
374                 kthread_stop(writer_task);
375         }
376         writer_task = NULL;
377
378         if (reader_tasks != NULL) {
379                 for (i = 0; i < nrealreaders; i++) {
380                         if (reader_tasks[i] != NULL) {
381                                 VERBOSE_PRINTK_STRING(
382                                         "Stopping rcu_torture_reader task");
383                                 kthread_stop(reader_tasks[i]);
384                         }
385                         reader_tasks[i] = NULL;
386                 }
387                 kfree(reader_tasks);
388                 reader_tasks = NULL;
389         }
390         rcu_torture_current = NULL;
391
392         if (stats_task != NULL) {
393                 VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
394                 kthread_stop(stats_task);
395         }
396         stats_task = NULL;
397
398         /* Wait for all RCU callbacks to fire.  */
399
400         for (i = 0; i < RCU_TORTURE_PIPE_LEN; i++)
401                 synchronize_rcu();
402         rcu_torture_stats_print();  /* -After- the stats thread is stopped! */
403         PRINTK_STRING("--- End of test");
404 }
405
406 static int
407 rcu_torture_init(void)
408 {
409         int i;
410         int cpu;
411         int firsterr = 0;
412
413         /* Process args and tell the world that the torturer is on the job. */
414
415         if (nreaders >= 0)
416                 nrealreaders = nreaders;
417         else
418                 nrealreaders = 2 * num_online_cpus();
419         printk(KERN_ALERT TORTURE_FLAG
420                "--- Start of test: nreaders=%d stat_interval=%d verbose=%d\n",
421                nrealreaders, stat_interval, verbose);
422         fullstop = 0;
423
424         /* Set up the freelist. */
425
426         INIT_LIST_HEAD(&rcu_torture_freelist);
427         for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
428                 list_add_tail(&rcu_tortures[i].rtort_free,
429                               &rcu_torture_freelist);
430         }
431
432         /* Initialize the statistics so that each run gets its own numbers. */
433
434         rcu_torture_current = NULL;
435         rcu_torture_current_version = 0;
436         atomic_set(&n_rcu_torture_alloc, 0);
437         atomic_set(&n_rcu_torture_alloc_fail, 0);
438         atomic_set(&n_rcu_torture_free, 0);
439         for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++)
440                 atomic_set(&rcu_torture_wcount[i], 0);
441         for_each_cpu(cpu) {
442                 for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
443                         per_cpu(rcu_torture_count, cpu)[i] = 0;
444                         per_cpu(rcu_torture_batch, cpu)[i] = 0;
445                 }
446         }
447
448         /* Start up the kthreads. */
449
450         VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
451         writer_task = kthread_run(rcu_torture_writer, NULL,
452                                   "rcu_torture_writer");
453         if (IS_ERR(writer_task)) {
454                 firsterr = PTR_ERR(writer_task);
455                 VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
456                 writer_task = NULL;
457                 goto unwind;
458         }
459         reader_tasks = kmalloc(nrealreaders * sizeof(reader_tasks[0]),
460                                GFP_KERNEL);
461         if (reader_tasks == NULL) {
462                 VERBOSE_PRINTK_ERRSTRING("out of memory");
463                 firsterr = -ENOMEM;
464                 goto unwind;
465         }
466         for (i = 0; i < nrealreaders; i++) {
467                 VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
468                 reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
469                                               "rcu_torture_reader");
470                 if (IS_ERR(reader_tasks[i])) {
471                         firsterr = PTR_ERR(reader_tasks[i]);
472                         VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
473                         reader_tasks[i] = NULL;
474                         goto unwind;
475                 }
476         }
477         if (stat_interval > 0) {
478                 VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
479                 stats_task = kthread_run(rcu_torture_stats, NULL,
480                                         "rcu_torture_stats");
481                 if (IS_ERR(stats_task)) {
482                         firsterr = PTR_ERR(stats_task);
483                         VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
484                         stats_task = NULL;
485                         goto unwind;
486                 }
487         }
488         return 0;
489
490 unwind:
491         rcu_torture_cleanup();
492         return firsterr;
493 }
494
495 module_init(rcu_torture_init);
496 module_exit(rcu_torture_cleanup);