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Date: Thu, 5 Mar 2020 00:40:11 +0800
From: kbuild test robot <lkp@...el.com>
To: "Paul E. McKenney" <paulmck@...nel.org>
Cc: kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org
Subject: [rcu:dev.2020.02.29a 43/43] kernel/rcu/tasks.h:369:2: error:
implicit declaration of function 'call_rcu_tasks_generic'
tree: https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2020.02.29a
head: 61f7110d6b78f4c84ea5d5480185740840889af7
commit: 61f7110d6b78f4c84ea5d5480185740840889af7 [43/43] rcu-tasks: Add an RCU-tasks rude variant
config: mips-rm200_defconfig (attached as .config)
compiler: mipsel-linux-gcc (GCC) 5.5.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
git checkout 61f7110d6b78f4c84ea5d5480185740840889af7
# save the attached .config to linux build tree
GCC_VERSION=5.5.0 make.cross ARCH=mips
If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@...el.com>
All error/warnings (new ones prefixed by >>):
union { typeof(x) __val; char __c[1]; } __u; \
^
kernel/rcu/tasks.h:212:7: note: in expansion of macro 'READ_ONCE'
if (!READ_ONCE(t->rcu_tasks_holdout) ||
^
kernel/rcu/tasks.h:212:18: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
if (!READ_ONCE(t->rcu_tasks_holdout) ||
^
include/linux/compiler.h:287:22: note: in definition of macro '__READ_ONCE'
__read_once_size(&(x), __u.__c, sizeof(x)); \
^
kernel/rcu/tasks.h:212:7: note: in expansion of macro 'READ_ONCE'
if (!READ_ONCE(t->rcu_tasks_holdout) ||
^
kernel/rcu/tasks.h:212:18: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
if (!READ_ONCE(t->rcu_tasks_holdout) ||
^
include/linux/compiler.h:287:42: note: in definition of macro '__READ_ONCE'
__read_once_size(&(x), __u.__c, sizeof(x)); \
^
kernel/rcu/tasks.h:212:7: note: in expansion of macro 'READ_ONCE'
if (!READ_ONCE(t->rcu_tasks_holdout) ||
^
kernel/rcu/tasks.h:212:18: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
if (!READ_ONCE(t->rcu_tasks_holdout) ||
^
include/linux/compiler.h:289:30: note: in definition of macro '__READ_ONCE'
__read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
^
kernel/rcu/tasks.h:212:7: note: in expansion of macro 'READ_ONCE'
if (!READ_ONCE(t->rcu_tasks_holdout) ||
^
kernel/rcu/tasks.h:212:18: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
if (!READ_ONCE(t->rcu_tasks_holdout) ||
^
include/linux/compiler.h:289:50: note: in definition of macro '__READ_ONCE'
__read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
^
kernel/rcu/tasks.h:212:7: note: in expansion of macro 'READ_ONCE'
if (!READ_ONCE(t->rcu_tasks_holdout) ||
^
In file included from kernel/rcu/update.c:562:0:
kernel/rcu/tasks.h:213:7: error: 'struct task_struct' has no member named 'rcu_tasks_nvcsw'
t->rcu_tasks_nvcsw != READ_ONCE(t->nvcsw) ||
^
kernel/rcu/tasks.h:216:28: error: 'struct task_struct' has no member named 'rcu_tasks_idle_cpu'
!is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) {
^
In file included from include/linux/kernel.h:11:0,
from kernel/rcu/update.c:21:
kernel/rcu/tasks.h:217:15: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
WRITE_ONCE(t->rcu_tasks_holdout, false);
^
include/linux/compiler.h:310:17: note: in definition of macro 'WRITE_ONCE'
union { typeof(x) __val; char __c[1]; } __u = \
^
kernel/rcu/tasks.h:217:15: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
WRITE_ONCE(t->rcu_tasks_holdout, false);
^
include/linux/compiler.h:311:30: note: in definition of macro 'WRITE_ONCE'
{ .__val = (__force typeof(x)) (val) }; \
^
kernel/rcu/tasks.h:217:15: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
WRITE_ONCE(t->rcu_tasks_holdout, false);
^
include/linux/compiler.h:312:22: note: in definition of macro 'WRITE_ONCE'
__write_once_size(&(x), __u.__c, sizeof(x)); \
^
kernel/rcu/tasks.h:217:15: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
WRITE_ONCE(t->rcu_tasks_holdout, false);
^
include/linux/compiler.h:312:42: note: in definition of macro 'WRITE_ONCE'
__write_once_size(&(x), __u.__c, sizeof(x)); \
^
In file included from kernel/rcu/update.c:562:0:
kernel/rcu/tasks.h:218:19: error: 'struct task_struct' has no member named 'rcu_tasks_holdout_list'
list_del_init(&t->rcu_tasks_holdout_list);
^
In file included from include/linux/kernel.h:15:0,
from kernel/rcu/update.c:21:
kernel/rcu/tasks.h:233:5: error: 'struct task_struct' has no member named 'rcu_tasks_nvcsw'
t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout,
^
include/linux/printk.h:300:35: note: in definition of macro 'pr_alert'
printk(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__)
^
kernel/rcu/tasks.h:233:35: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout,
^
include/linux/printk.h:300:35: note: in definition of macro 'pr_alert'
printk(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__)
^
kernel/rcu/tasks.h:234:5: error: 'struct task_struct' has no member named 'rcu_tasks_idle_cpu'
t->rcu_tasks_idle_cpu, cpu);
^
include/linux/printk.h:300:35: note: in definition of macro 'pr_alert'
printk(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__)
^
In file included from kernel/rcu/update.c:562:0:
kernel/rcu/tasks.h: At top level:
>> kernel/rcu/tasks.h:239:38: warning: 'struct rcu_tasks' declared inside parameter list
static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)
^
>> kernel/rcu/tasks.h:239:38: warning: its scope is only this definition or declaration, which is probably not what you want
kernel/rcu/tasks.h: In function 'rcu_tasks_wait_gp':
kernel/rcu/tasks.h:271:5: error: 'struct task_struct' has no member named 'rcu_tasks_nvcsw'
t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw);
^
In file included from include/linux/kernel.h:11:0,
from kernel/rcu/update.c:21:
kernel/rcu/tasks.h:272:16: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
WRITE_ONCE(t->rcu_tasks_holdout, true);
^
include/linux/compiler.h:310:17: note: in definition of macro 'WRITE_ONCE'
union { typeof(x) __val; char __c[1]; } __u = \
^
kernel/rcu/tasks.h:272:16: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
WRITE_ONCE(t->rcu_tasks_holdout, true);
^
include/linux/compiler.h:311:30: note: in definition of macro 'WRITE_ONCE'
{ .__val = (__force typeof(x)) (val) }; \
^
kernel/rcu/tasks.h:272:16: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
WRITE_ONCE(t->rcu_tasks_holdout, true);
^
include/linux/compiler.h:312:22: note: in definition of macro 'WRITE_ONCE'
__write_once_size(&(x), __u.__c, sizeof(x)); \
^
kernel/rcu/tasks.h:272:16: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
WRITE_ONCE(t->rcu_tasks_holdout, true);
^
include/linux/compiler.h:312:42: note: in definition of macro 'WRITE_ONCE'
__write_once_size(&(x), __u.__c, sizeof(x)); \
^
In file included from kernel/rcu/update.c:562:0:
kernel/rcu/tasks.h:273:15: error: 'struct task_struct' has no member named 'rcu_tasks_holdout_list'
list_add(&t->rcu_tasks_holdout_list,
^
kernel/rcu/tasks.h:286:20: error: 'tasks_rcu_exit_srcu' undeclared (first use in this function)
synchronize_srcu(&tasks_rcu_exit_srcu);
^
kernel/rcu/tasks.h:286:20: note: each undeclared identifier is reported only once for each function it appears in
In file included from include/linux/kernel.h:11:0,
from kernel/rcu/update.c:21:
kernel/rcu/tasks.h:313:20: error: 'rcu_task_stall_timeout' undeclared (first use in this function)
rtst = READ_ONCE(rcu_task_stall_timeout);
^
include/linux/compiler.h:285:17: note: in definition of macro '__READ_ONCE'
union { typeof(x) __val; char __c[1]; } __u; \
^
kernel/rcu/tasks.h:313:10: note: in expansion of macro 'READ_ONCE'
rtst = READ_ONCE(rcu_task_stall_timeout);
^
include/linux/kernel.h:987:51: error: 'struct task_struct' has no member named 'rcu_tasks_holdout_list'
BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
^
include/linux/compiler.h:374:9: note: in definition of macro '__compiletime_assert'
if (!(condition)) \
^
include/linux/compiler.h:394:2: note: in expansion of macro '_compiletime_assert'
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^
include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
^
include/linux/kernel.h:987:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
^
include/linux/kernel.h:987:20: note: in expansion of macro '__same_type'
BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
^
include/linux/list.h:493:2: note: in expansion of macro 'container_of'
container_of(ptr, type, member)
^
include/linux/list.h:504:2: note: in expansion of macro 'list_entry'
list_entry((ptr)->next, type, member)
^
include/linux/list.h:688:13: note: in expansion of macro 'list_first_entry'
for (pos = list_first_entry(head, typeof(*pos), member), \
^
kernel/rcu/tasks.h:319:3: note: in expansion of macro 'list_for_each_entry_safe'
list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
^
In file included from <command-line>:0:0:
include/linux/compiler_types.h:129:35: error: 'struct task_struct' has no member named 'rcu_tasks_holdout_list'
#define __compiler_offsetof(a, b) __builtin_offsetof(a, b)
^
include/linux/stddef.h:17:32: note: in expansion of macro '__compiler_offsetof'
#define offsetof(TYPE, MEMBER) __compiler_offsetof(TYPE, MEMBER)
^
include/linux/kernel.h:990:21: note: in expansion of macro 'offsetof'
((type *)(__mptr - offsetof(type, member))); })
^
include/linux/list.h:493:2: note: in expansion of macro 'container_of'
container_of(ptr, type, member)
^
include/linux/list.h:504:2: note: in expansion of macro 'list_entry'
list_entry((ptr)->next, type, member)
^
include/linux/list.h:688:13: note: in expansion of macro 'list_first_entry'
for (pos = list_first_entry(head, typeof(*pos), member), \
^
kernel/rcu/tasks.h:319:3: note: in expansion of macro 'list_for_each_entry_safe'
list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
--
^
include/linux/list.h:537:2: note: in expansion of macro 'list_entry'
list_entry((pos)->member.next, typeof(*(pos)), member)
^
include/linux/list.h:691:20: note: in expansion of macro 'list_next_entry'
pos = n, n = list_next_entry(n, member))
^
kernel/rcu/tasks.h:319:3: note: in expansion of macro 'list_for_each_entry_safe'
list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
^
include/linux/kernel.h:987:51: error: 'struct task_struct' has no member named 'rcu_tasks_holdout_list'
BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
^
include/linux/compiler.h:374:9: note: in definition of macro '__compiletime_assert'
if (!(condition)) \
^
include/linux/compiler.h:394:2: note: in expansion of macro '_compiletime_assert'
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^
include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
^
include/linux/kernel.h:987:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
^
include/linux/kernel.h:987:20: note: in expansion of macro '__same_type'
BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
^
include/linux/list.h:493:2: note: in expansion of macro 'container_of'
container_of(ptr, type, member)
^
include/linux/list.h:537:2: note: in expansion of macro 'list_entry'
list_entry((pos)->member.next, typeof(*(pos)), member)
^
include/linux/list.h:691:20: note: in expansion of macro 'list_next_entry'
pos = n, n = list_next_entry(n, member))
^
kernel/rcu/tasks.h:319:3: note: in expansion of macro 'list_for_each_entry_safe'
list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
^
include/linux/list.h:537:18: error: 'struct task_struct' has no member named 'rcu_tasks_holdout_list'
list_entry((pos)->member.next, typeof(*(pos)), member)
^
include/linux/compiler.h:374:9: note: in definition of macro '__compiletime_assert'
if (!(condition)) \
^
include/linux/compiler.h:394:2: note: in expansion of macro '_compiletime_assert'
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^
include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
^
include/linux/kernel.h:987:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
^
include/linux/kernel.h:988:6: note: in expansion of macro '__same_type'
!__same_type(*(ptr), void), \
^
include/linux/list.h:493:2: note: in expansion of macro 'container_of'
container_of(ptr, type, member)
^
include/linux/list.h:537:2: note: in expansion of macro 'list_entry'
list_entry((pos)->member.next, typeof(*(pos)), member)
^
include/linux/list.h:691:20: note: in expansion of macro 'list_next_entry'
pos = n, n = list_next_entry(n, member))
^
kernel/rcu/tasks.h:319:3: note: in expansion of macro 'list_for_each_entry_safe'
list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
^
In file included from <command-line>:0:0:
include/linux/compiler_types.h:129:35: error: 'struct task_struct' has no member named 'rcu_tasks_holdout_list'
#define __compiler_offsetof(a, b) __builtin_offsetof(a, b)
^
include/linux/stddef.h:17:32: note: in expansion of macro '__compiler_offsetof'
#define offsetof(TYPE, MEMBER) __compiler_offsetof(TYPE, MEMBER)
^
include/linux/kernel.h:990:21: note: in expansion of macro 'offsetof'
((type *)(__mptr - offsetof(type, member))); })
^
include/linux/list.h:493:2: note: in expansion of macro 'container_of'
container_of(ptr, type, member)
^
include/linux/list.h:537:2: note: in expansion of macro 'list_entry'
list_entry((pos)->member.next, typeof(*(pos)), member)
^
include/linux/list.h:691:20: note: in expansion of macro 'list_next_entry'
pos = n, n = list_next_entry(n, member))
^
kernel/rcu/tasks.h:319:3: note: in expansion of macro 'list_for_each_entry_safe'
list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
^
In file included from kernel/rcu/update.c:562:0:
kernel/rcu/tasks.h: At top level:
kernel/rcu/tasks.h:347:1: warning: data definition has no type or storage class
DEFINE_RCU_TASKS(rcu_tasks, rcu_tasks_wait_gp, call_rcu_tasks);
^
kernel/rcu/tasks.h:347:1: error: type defaults to 'int' in declaration of 'DEFINE_RCU_TASKS' [-Werror=implicit-int]
kernel/rcu/tasks.h:347:1: warning: parameter names (without types) in function declaration
kernel/rcu/tasks.h: In function 'call_rcu':
>> kernel/rcu/tasks.h:369:2: error: implicit declaration of function 'call_rcu_tasks_generic' [-Werror=implicit-function-declaration]
call_rcu_tasks_generic(rhp, func, &rcu_tasks);
^
>> kernel/rcu/tasks.h:369:37: error: 'rcu_tasks' undeclared (first use in this function)
call_rcu_tasks_generic(rhp, func, &rcu_tasks);
^
kernel/rcu/tasks.h: In function 'synchronize_rcu':
>> kernel/rcu/tasks.h:393:2: error: implicit declaration of function 'synchronize_rcu_tasks_generic' [-Werror=implicit-function-declaration]
synchronize_rcu_tasks_generic(&rcu_tasks);
^
kernel/rcu/tasks.h:393:33: error: 'rcu_tasks' undeclared (first use in this function)
synchronize_rcu_tasks_generic(&rcu_tasks);
^
kernel/rcu/tasks.h: In function 'rcu_spawn_tasks_kthread':
>> kernel/rcu/tasks.h:412:2: error: implicit declaration of function 'rcu_spawn_tasks_kthread_generic' [-Werror=implicit-function-declaration]
rcu_spawn_tasks_kthread_generic(&rcu_tasks);
^
kernel/rcu/tasks.h:412:35: error: 'rcu_tasks' undeclared (first use in this function)
rcu_spawn_tasks_kthread_generic(&rcu_tasks);
^
kernel/rcu/tasks.h: At top level:
kernel/rcu/tasks.h:432:43: warning: 'struct rcu_tasks' declared inside parameter list
static void rcu_tasks_rude_wait_gp(struct rcu_tasks *rtp)
^
kernel/rcu/tasks.h:439:1: warning: data definition has no type or storage class
DEFINE_RCU_TASKS(rcu_tasks_rude, rcu_tasks_rude_wait_gp, call_rcu_tasks_rude);
^
kernel/rcu/tasks.h:439:1: error: type defaults to 'int' in declaration of 'DEFINE_RCU_TASKS' [-Werror=implicit-int]
kernel/rcu/tasks.h:439:1: warning: parameter names (without types) in function declaration
kernel/rcu/tasks.h: In function 'call_rcu_tasks_rude':
>> kernel/rcu/tasks.h:461:37: error: 'rcu_tasks_rude' undeclared (first use in this function)
call_rcu_tasks_generic(rhp, func, &rcu_tasks_rude);
^
kernel/rcu/tasks.h: In function 'synchronize_rcu_tasks_rude':
kernel/rcu/tasks.h:485:33: error: 'rcu_tasks_rude' undeclared (first use in this function)
synchronize_rcu_tasks_generic(&rcu_tasks_rude);
^
kernel/rcu/tasks.h: In function 'rcu_spawn_tasks_rude_kthread':
kernel/rcu/tasks.h:504:35: error: 'rcu_tasks_rude' undeclared (first use in this function)
rcu_spawn_tasks_kthread_generic(&rcu_tasks_rude);
^
kernel/rcu/update.c: At top level:
kernel/rcu/tasks.h:239:13: warning: 'rcu_tasks_wait_gp' defined but not used [-Wunused-function]
static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)
^
cc1: some warnings being treated as errors
vim +/call_rcu_tasks_generic +369 kernel/rcu/tasks.h
237
238 /* Wait for one RCU-tasks grace period. */
> 239 static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)
240 {
241 struct task_struct *g, *t;
242 unsigned long lastreport;
243 LIST_HEAD(rcu_tasks_holdouts);
244 int fract;
245
246 /*
247 * Wait for all pre-existing t->on_rq and t->nvcsw transitions
248 * to complete. Invoking synchronize_rcu() suffices because all
249 * these transitions occur with interrupts disabled. Without this
250 * synchronize_rcu(), a read-side critical section that started
251 * before the grace period might be incorrectly seen as having
252 * started after the grace period.
253 *
254 * This synchronize_rcu() also dispenses with the need for a
255 * memory barrier on the first store to t->rcu_tasks_holdout,
256 * as it forces the store to happen after the beginning of the
257 * grace period.
258 */
259 synchronize_rcu();
260
261 /*
262 * There were callbacks, so we need to wait for an RCU-tasks
263 * grace period. Start off by scanning the task list for tasks
264 * that are not already voluntarily blocked. Mark these tasks
265 * and make a list of them in rcu_tasks_holdouts.
266 */
267 rcu_read_lock();
268 for_each_process_thread(g, t) {
269 if (t != current && READ_ONCE(t->on_rq) && !is_idle_task(t)) {
270 get_task_struct(t);
271 t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw);
272 WRITE_ONCE(t->rcu_tasks_holdout, true);
273 list_add(&t->rcu_tasks_holdout_list,
274 &rcu_tasks_holdouts);
275 }
276 }
277 rcu_read_unlock();
278
279 /*
280 * Wait for tasks that are in the process of exiting. This
281 * does only part of the job, ensuring that all tasks that were
282 * previously exiting reach the point where they have disabled
283 * preemption, allowing the later synchronize_rcu() to finish
284 * the job.
285 */
286 synchronize_srcu(&tasks_rcu_exit_srcu);
287
288 /*
289 * Each pass through the following loop scans the list of holdout
290 * tasks, removing any that are no longer holdouts. When the list
291 * is empty, we are done.
292 */
293 lastreport = jiffies;
294
295 /* Start off with HZ/10 wait and slowly back off to 1 HZ wait. */
296 fract = 10;
297
298 for (;;) {
299 bool firstreport;
300 bool needreport;
301 int rtst;
302 struct task_struct *t1;
303
304 if (list_empty(&rcu_tasks_holdouts))
305 break;
306
307 /* Slowly back off waiting for holdouts */
308 schedule_timeout_interruptible(HZ/fract);
309
310 if (fract > 1)
311 fract--;
312
313 rtst = READ_ONCE(rcu_task_stall_timeout);
314 needreport = rtst > 0 && time_after(jiffies, lastreport + rtst);
315 if (needreport)
316 lastreport = jiffies;
317 firstreport = true;
318 WARN_ON(signal_pending(current));
319 list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
320 rcu_tasks_holdout_list) {
321 check_holdout_task(t, needreport, &firstreport);
322 cond_resched();
323 }
324 }
325
326 /*
327 * Because ->on_rq and ->nvcsw are not guaranteed to have a full
328 * memory barriers prior to them in the schedule() path, memory
329 * reordering on other CPUs could cause their RCU-tasks read-side
330 * critical sections to extend past the end of the grace period.
331 * However, because these ->nvcsw updates are carried out with
332 * interrupts disabled, we can use synchronize_rcu() to force the
333 * needed ordering on all such CPUs.
334 *
335 * This synchronize_rcu() also confines all ->rcu_tasks_holdout
336 * accesses to be within the grace period, avoiding the need for
337 * memory barriers for ->rcu_tasks_holdout accesses.
338 *
339 * In addition, this synchronize_rcu() waits for exiting tasks
340 * to complete their final preempt_disable() region of execution,
341 * cleaning up after the synchronize_srcu() above.
342 */
343 synchronize_rcu();
344 }
345
346 void call_rcu_tasks(struct rcu_head *rhp, rcu_callback_t func);
347 DEFINE_RCU_TASKS(rcu_tasks, rcu_tasks_wait_gp, call_rcu_tasks);
348
349 /**
350 * call_rcu_tasks() - Queue an RCU for invocation task-based grace period
351 * @rhp: structure to be used for queueing the RCU updates.
352 * @func: actual callback function to be invoked after the grace period
353 *
354 * The callback function will be invoked some time after a full grace
355 * period elapses, in other words after all currently executing RCU
356 * read-side critical sections have completed. call_rcu_tasks() assumes
357 * that the read-side critical sections end at a voluntary context
358 * switch (not a preemption!), cond_resched_rcu_qs(), entry into idle,
359 * or transition to usermode execution. As such, there are no read-side
360 * primitives analogous to rcu_read_lock() and rcu_read_unlock() because
361 * this primitive is intended to determine that all tasks have passed
362 * through a safe state, not so much for data-strcuture synchronization.
363 *
364 * See the description of call_rcu() for more detailed information on
365 * memory ordering guarantees.
366 */
367 void call_rcu_tasks(struct rcu_head *rhp, rcu_callback_t func)
368 {
> 369 call_rcu_tasks_generic(rhp, func, &rcu_tasks);
370 }
371 EXPORT_SYMBOL_GPL(call_rcu_tasks);
372
373 /**
374 * synchronize_rcu_tasks - wait until an rcu-tasks grace period has elapsed.
375 *
376 * Control will return to the caller some time after a full rcu-tasks
377 * grace period has elapsed, in other words after all currently
378 * executing rcu-tasks read-side critical sections have elapsed. These
379 * read-side critical sections are delimited by calls to schedule(),
380 * cond_resched_tasks_rcu_qs(), idle execution, userspace execution, calls
381 * to synchronize_rcu_tasks(), and (in theory, anyway) cond_resched().
382 *
383 * This is a very specialized primitive, intended only for a few uses in
384 * tracing and other situations requiring manipulation of function
385 * preambles and profiling hooks. The synchronize_rcu_tasks() function
386 * is not (yet) intended for heavy use from multiple CPUs.
387 *
388 * See the description of synchronize_rcu() for more detailed information
389 * on memory ordering guarantees.
390 */
391 void synchronize_rcu_tasks(void)
392 {
> 393 synchronize_rcu_tasks_generic(&rcu_tasks);
394 }
395 EXPORT_SYMBOL_GPL(synchronize_rcu_tasks);
396
397 /**
398 * rcu_barrier_tasks - Wait for in-flight call_rcu_tasks() callbacks.
399 *
400 * Although the current implementation is guaranteed to wait, it is not
401 * obligated to, for example, if there are no pending callbacks.
402 */
403 void rcu_barrier_tasks(void)
404 {
405 /* There is only one callback queue, so this is easy. ;-) */
406 synchronize_rcu_tasks();
407 }
408 EXPORT_SYMBOL_GPL(rcu_barrier_tasks);
409
410 static int __init rcu_spawn_tasks_kthread(void)
411 {
> 412 rcu_spawn_tasks_kthread_generic(&rcu_tasks);
413 return 0;
414 }
415 core_initcall(rcu_spawn_tasks_kthread);
416
417 ////////////////////////////////////////////////////////////////////////
418 //
419 // "Rude" variant of Tasks RCU, inspired by Steve Rostedt's trick of
420 // passing an empty function to schedule_on_each_cpu(). This approach
421 // provides an asynchronous call_rcu_rude() API and batching of concurrent
422 // calls to the synchronous synchronize_rcu_rude() API. This sends IPIs
423 // far and wide and induces otherwise unnecessary context switches on all
424 // online CPUs, whether online or not.
425
426 // Empty function to allow workqueues to force a context switch.
427 static void rcu_tasks_be_rude(struct work_struct *work)
428 {
429 }
430
431 // Wait for one rude RCU-tasks grace period.
432 static void rcu_tasks_rude_wait_gp(struct rcu_tasks *rtp)
433 {
434 schedule_on_each_cpu(rcu_tasks_be_rude);
435 }
436 EXPORT_SYMBOL_GPL(rcu_tasks_rude_wait_gp);
437
438 void call_rcu_tasks_rude(struct rcu_head *rhp, rcu_callback_t func);
439 DEFINE_RCU_TASKS(rcu_tasks_rude, rcu_tasks_rude_wait_gp, call_rcu_tasks_rude);
440
441 /**
442 * call_rcu_tasks_rude() - Queue a callback rude task-based grace period
443 * @rhp: structure to be used for queueing the RCU updates.
444 * @func: actual callback function to be invoked after the grace period
445 *
446 * The callback function will be invoked some time after a full grace
447 * period elapses, in other words after all currently executing RCU
448 * read-side critical sections have completed. call_rcu_tasks_rude()
449 * assumes that the read-side critical sections end at context switch,
450 * cond_resched_rcu_qs(), or transition to usermode execution. As such,
451 * there are no read-side primitives analogous to rcu_read_lock() and
452 * rcu_read_unlock() because this primitive is intended to determine
453 * that all tasks have passed through a safe state, not so much for
454 * data-strcuture synchronization.
455 *
456 * See the description of call_rcu() for more detailed information on
457 * memory ordering guarantees.
458 */
459 void call_rcu_tasks_rude(struct rcu_head *rhp, rcu_callback_t func)
460 {
> 461 call_rcu_tasks_generic(rhp, func, &rcu_tasks_rude);
462 }
463 EXPORT_SYMBOL_GPL(call_rcu_tasks_rude);
464
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