ia64/xen-unstable

view xen/common/rcupdate.c @ 19835:edfdeb150f27

Fix buildsystem to detect udev > version 124

udev removed the udevinfo symlink from versions higher than 123 and
xen's build-system could not detect if udev is in place and has the
required version.

Signed-off-by: Marc-A. Dahlhaus <mad@wol.de>
author Keir Fraser <keir.fraser@citrix.com>
date Thu Jun 25 13:02:37 2009 +0100 (2009-06-25)
parents 759d924af6d8
children
line source
1 /*
2 * Read-Copy Update mechanism for mutual exclusion
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, 2001
19 *
20 * Authors: Dipankar Sarma <dipankar@in.ibm.com>
21 * Manfred Spraul <manfred@colorfullife.com>
22 *
23 * Modifications for Xen: Jose Renato Santos
24 * Copyright (C) Hewlett-Packard, 2006
25 *
26 * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
27 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
28 * Papers:
29 * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
30 * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
31 *
32 * For detailed explanation of Read-Copy Update mechanism see -
33 * http://lse.sourceforge.net/locking/rcupdate.html
34 */
35 #include <xen/types.h>
36 #include <xen/kernel.h>
37 #include <xen/init.h>
38 #include <xen/spinlock.h>
39 #include <xen/smp.h>
40 #include <xen/rcupdate.h>
41 #include <xen/sched.h>
42 #include <asm/atomic.h>
43 #include <xen/bitops.h>
44 #include <xen/percpu.h>
45 #include <xen/softirq.h>
47 /* Definition for rcupdate control block. */
48 struct rcu_ctrlblk rcu_ctrlblk = {
49 .cur = -300,
50 .completed = -300,
51 .lock = SPIN_LOCK_UNLOCKED,
52 .cpumask = CPU_MASK_NONE,
53 };
55 DEFINE_PER_CPU(struct rcu_data, rcu_data) = { 0L };
57 static int blimit = 10;
58 static int qhimark = 10000;
59 static int qlowmark = 100;
60 static int rsinterval = 1000;
62 static void force_quiescent_state(struct rcu_data *rdp,
63 struct rcu_ctrlblk *rcp)
64 {
65 cpumask_t cpumask;
66 raise_softirq(SCHEDULE_SOFTIRQ);
67 if (unlikely(rdp->qlen - rdp->last_rs_qlen > rsinterval)) {
68 rdp->last_rs_qlen = rdp->qlen;
69 /*
70 * Don't send IPI to itself. With irqs disabled,
71 * rdp->cpu is the current cpu.
72 */
73 cpumask = rcp->cpumask;
74 cpu_clear(rdp->cpu, cpumask);
75 cpumask_raise_softirq(cpumask, SCHEDULE_SOFTIRQ);
76 }
77 }
79 /**
80 * call_rcu - Queue an RCU callback for invocation after a grace period.
81 * @head: structure to be used for queueing the RCU updates.
82 * @func: actual update function to be invoked after the grace period
83 *
84 * The update function will be invoked some time after a full grace
85 * period elapses, in other words after all currently executing RCU
86 * read-side critical sections have completed. RCU read-side critical
87 * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
88 * and may be nested.
89 */
90 void fastcall call_rcu(struct rcu_head *head,
91 void (*func)(struct rcu_head *rcu))
92 {
93 unsigned long flags;
94 struct rcu_data *rdp;
96 head->func = func;
97 head->next = NULL;
98 local_irq_save(flags);
99 rdp = &__get_cpu_var(rcu_data);
100 *rdp->nxttail = head;
101 rdp->nxttail = &head->next;
102 if (unlikely(++rdp->qlen > qhimark)) {
103 rdp->blimit = INT_MAX;
104 force_quiescent_state(rdp, &rcu_ctrlblk);
105 }
106 local_irq_restore(flags);
107 }
109 /*
110 * Invoke the completed RCU callbacks. They are expected to be in
111 * a per-cpu list.
112 */
113 static void rcu_do_batch(struct rcu_data *rdp)
114 {
115 struct rcu_head *next, *list;
116 int count = 0;
118 list = rdp->donelist;
119 while (list) {
120 next = rdp->donelist = list->next;
121 list->func(list);
122 list = next;
123 rdp->qlen--;
124 if (++count >= rdp->blimit)
125 break;
126 }
127 if (rdp->blimit == INT_MAX && rdp->qlen <= qlowmark)
128 rdp->blimit = blimit;
129 if (!rdp->donelist)
130 rdp->donetail = &rdp->donelist;
131 else
132 raise_softirq(RCU_SOFTIRQ);
133 }
135 /*
136 * Grace period handling:
137 * The grace period handling consists out of two steps:
138 * - A new grace period is started.
139 * This is done by rcu_start_batch. The start is not broadcasted to
140 * all cpus, they must pick this up by comparing rcp->cur with
141 * rdp->quiescbatch. All cpus are recorded in the
142 * rcu_ctrlblk.cpumask bitmap.
143 * - All cpus must go through a quiescent state.
144 * Since the start of the grace period is not broadcasted, at least two
145 * calls to rcu_check_quiescent_state are required:
146 * The first call just notices that a new grace period is running. The
147 * following calls check if there was a quiescent state since the beginning
148 * of the grace period. If so, it updates rcu_ctrlblk.cpumask. If
149 * the bitmap is empty, then the grace period is completed.
150 * rcu_check_quiescent_state calls rcu_start_batch(0) to start the next grace
151 * period (if necessary).
152 */
153 /*
154 * Register a new batch of callbacks, and start it up if there is currently no
155 * active batch and the batch to be registered has not already occurred.
156 * Caller must hold rcu_ctrlblk.lock.
157 */
158 static void rcu_start_batch(struct rcu_ctrlblk *rcp)
159 {
160 if (rcp->next_pending &&
161 rcp->completed == rcp->cur) {
162 rcp->next_pending = 0;
163 /*
164 * next_pending == 0 must be visible in
165 * __rcu_process_callbacks() before it can see new value of cur.
166 */
167 smp_wmb();
168 rcp->cur++;
170 rcp->cpumask = cpu_online_map;
171 }
172 }
174 /*
175 * cpu went through a quiescent state since the beginning of the grace period.
176 * Clear it from the cpu mask and complete the grace period if it was the last
177 * cpu. Start another grace period if someone has further entries pending
178 */
179 static void cpu_quiet(int cpu, struct rcu_ctrlblk *rcp)
180 {
181 cpu_clear(cpu, rcp->cpumask);
182 if (cpus_empty(rcp->cpumask)) {
183 /* batch completed ! */
184 rcp->completed = rcp->cur;
185 rcu_start_batch(rcp);
186 }
187 }
189 /*
190 * Check if the cpu has gone through a quiescent state (say context
191 * switch). If so and if it already hasn't done so in this RCU
192 * quiescent cycle, then indicate that it has done so.
193 */
194 static void rcu_check_quiescent_state(struct rcu_ctrlblk *rcp,
195 struct rcu_data *rdp)
196 {
197 if (rdp->quiescbatch != rcp->cur) {
198 /* start new grace period: */
199 rdp->qs_pending = 1;
200 rdp->quiescbatch = rcp->cur;
201 return;
202 }
204 /* Grace period already completed for this cpu?
205 * qs_pending is checked instead of the actual bitmap to avoid
206 * cacheline trashing.
207 */
208 if (!rdp->qs_pending)
209 return;
211 rdp->qs_pending = 0;
213 spin_lock(&rcp->lock);
214 /*
215 * rdp->quiescbatch/rcp->cur and the cpu bitmap can come out of sync
216 * during cpu startup. Ignore the quiescent state.
217 */
218 if (likely(rdp->quiescbatch == rcp->cur))
219 cpu_quiet(rdp->cpu, rcp);
221 spin_unlock(&rcp->lock);
222 }
225 /*
226 * This does the RCU processing work from softirq context.
227 */
228 static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp,
229 struct rcu_data *rdp)
230 {
231 if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch)) {
232 *rdp->donetail = rdp->curlist;
233 rdp->donetail = rdp->curtail;
234 rdp->curlist = NULL;
235 rdp->curtail = &rdp->curlist;
236 }
238 local_irq_disable();
239 if (rdp->nxtlist && !rdp->curlist) {
240 rdp->curlist = rdp->nxtlist;
241 rdp->curtail = rdp->nxttail;
242 rdp->nxtlist = NULL;
243 rdp->nxttail = &rdp->nxtlist;
244 local_irq_enable();
246 /*
247 * start the next batch of callbacks
248 */
250 /* determine batch number */
251 rdp->batch = rcp->cur + 1;
252 /* see the comment and corresponding wmb() in
253 * the rcu_start_batch()
254 */
255 smp_rmb();
257 if (!rcp->next_pending) {
258 /* and start it/schedule start if it's a new batch */
259 spin_lock(&rcp->lock);
260 rcp->next_pending = 1;
261 rcu_start_batch(rcp);
262 spin_unlock(&rcp->lock);
263 }
264 } else {
265 local_irq_enable();
266 }
267 rcu_check_quiescent_state(rcp, rdp);
268 if (rdp->donelist)
269 rcu_do_batch(rdp);
270 }
272 static void rcu_process_callbacks(void)
273 {
274 __rcu_process_callbacks(&rcu_ctrlblk, &__get_cpu_var(rcu_data));
275 }
277 static int __rcu_pending(struct rcu_ctrlblk *rcp, struct rcu_data *rdp)
278 {
279 /* This cpu has pending rcu entries and the grace period
280 * for them has completed.
281 */
282 if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch))
283 return 1;
285 /* This cpu has no pending entries, but there are new entries */
286 if (!rdp->curlist && rdp->nxtlist)
287 return 1;
289 /* This cpu has finished callbacks to invoke */
290 if (rdp->donelist)
291 return 1;
293 /* The rcu core waits for a quiescent state from the cpu */
294 if (rdp->quiescbatch != rcp->cur || rdp->qs_pending)
295 return 1;
297 /* nothing to do */
298 return 0;
299 }
301 int rcu_pending(int cpu)
302 {
303 return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu));
304 }
306 /*
307 * Check to see if any future RCU-related work will need to be done
308 * by the current CPU, even if none need be done immediately, returning
309 * 1 if so. This function is part of the RCU implementation; it is -not-
310 * an exported member of the RCU API.
311 */
312 int rcu_needs_cpu(int cpu)
313 {
314 struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
316 return (!!rdp->curlist || rcu_pending(cpu));
317 }
319 void rcu_check_callbacks(int cpu)
320 {
321 raise_softirq(RCU_SOFTIRQ);
322 }
324 static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
325 struct rcu_data *rdp)
326 {
327 memset(rdp, 0, sizeof(*rdp));
328 rdp->curtail = &rdp->curlist;
329 rdp->nxttail = &rdp->nxtlist;
330 rdp->donetail = &rdp->donelist;
331 rdp->quiescbatch = rcp->completed;
332 rdp->qs_pending = 0;
333 rdp->cpu = cpu;
334 rdp->blimit = blimit;
335 }
337 void __devinit rcu_online_cpu(int cpu)
338 {
339 struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
341 rcu_init_percpu_data(cpu, &rcu_ctrlblk, rdp);
342 }
344 void __init rcu_init(void)
345 {
346 rcu_online_cpu(smp_processor_id());
347 open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
348 }