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Message-ID: <202003042222.GBTOCQ9I%lkp@intel.com>
Date:   Wed, 4 Mar 2020 22:43:25 +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:313:20: error:
 'rcu_task_stall_timeout' undeclared

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: nds32-allnoconfig (attached as .config)
compiler: nds32le-linux-gcc (GCC) 9.2.0
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=9.2.0 make.cross ARCH=nds32 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@...el.com>

All errors (new ones prefixed by >>):

     213 |      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'
     216 |       !is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) {
         |                            ^~
   In file included from include/linux/kernel.h:11,
                    from kernel/rcu/update.c:21:
   kernel/rcu/tasks.h:217:15: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
     217 |   WRITE_ONCE(t->rcu_tasks_holdout, false);
         |               ^~
   include/linux/compiler.h:310:17: note: in definition of macro 'WRITE_ONCE'
     310 |  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'
     217 |   WRITE_ONCE(t->rcu_tasks_holdout, false);
         |               ^~
   include/linux/compiler.h:311:30: note: in definition of macro 'WRITE_ONCE'
     311 |   { .__val = (__force typeof(x)) (val) }; \
         |                              ^
   kernel/rcu/tasks.h:217:15: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
     217 |   WRITE_ONCE(t->rcu_tasks_holdout, false);
         |               ^~
   include/linux/compiler.h:312:22: note: in definition of macro 'WRITE_ONCE'
     312 |  __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'
     217 |   WRITE_ONCE(t->rcu_tasks_holdout, false);
         |               ^~
   include/linux/compiler.h:312:42: note: in definition of macro 'WRITE_ONCE'
     312 |  __write_once_size(&(x), __u.__c, sizeof(x)); \
         |                                          ^
   In file included from kernel/rcu/update.c:562:
   kernel/rcu/tasks.h:218:19: error: 'struct task_struct' has no member named 'rcu_tasks_holdout_list'
     218 |   list_del_init(&t->rcu_tasks_holdout_list);
         |                   ^~
   In file included from include/linux/kernel.h:15,
                    from kernel/rcu/update.c:21:
   kernel/rcu/tasks.h:233:5: error: 'struct task_struct' has no member named 'rcu_tasks_nvcsw'
     233 |    t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout,
         |     ^~
   include/linux/printk.h:300:35: note: in definition of macro 'pr_alert'
     300 |  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'
     233 |    t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout,
         |                                   ^~
   include/linux/printk.h:300:35: note: in definition of macro 'pr_alert'
     300 |  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'
     234 |    t->rcu_tasks_idle_cpu, cpu);
         |     ^~
   include/linux/printk.h:300:35: note: in definition of macro 'pr_alert'
     300 |  printk(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__)
         |                                   ^~~~~~~~~~~
   In file included from kernel/rcu/update.c:562:
   kernel/rcu/tasks.h: At top level:
   kernel/rcu/tasks.h:239:38: warning: 'struct rcu_tasks' declared inside parameter list will not be visible outside of this definition or declaration
     239 | static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)
         |                                      ^~~~~~~~~
   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'
     271 |    t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw);
         |     ^~
   In file included from include/linux/kernel.h:11,
                    from kernel/rcu/update.c:21:
   kernel/rcu/tasks.h:272:16: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
     272 |    WRITE_ONCE(t->rcu_tasks_holdout, true);
         |                ^~
   include/linux/compiler.h:310:17: note: in definition of macro 'WRITE_ONCE'
     310 |  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'
     272 |    WRITE_ONCE(t->rcu_tasks_holdout, true);
         |                ^~
   include/linux/compiler.h:311:30: note: in definition of macro 'WRITE_ONCE'
     311 |   { .__val = (__force typeof(x)) (val) }; \
         |                              ^
   kernel/rcu/tasks.h:272:16: error: 'struct task_struct' has no member named 'rcu_tasks_holdout'
     272 |    WRITE_ONCE(t->rcu_tasks_holdout, true);
         |                ^~
   include/linux/compiler.h:312:22: note: in definition of macro 'WRITE_ONCE'
     312 |  __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'
     272 |    WRITE_ONCE(t->rcu_tasks_holdout, true);
         |                ^~
   include/linux/compiler.h:312:42: note: in definition of macro 'WRITE_ONCE'
     312 |  __write_once_size(&(x), __u.__c, sizeof(x)); \
         |                                          ^
   In file included from kernel/rcu/update.c:562:
   kernel/rcu/tasks.h:273:15: error: 'struct task_struct' has no member named 'rcu_tasks_holdout_list'
     273 |    list_add(&t->rcu_tasks_holdout_list,
         |               ^~
   kernel/rcu/tasks.h:286:20: error: 'tasks_rcu_exit_srcu' undeclared (first use in this function)
     286 |  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,
                    from kernel/rcu/update.c:21:
>> kernel/rcu/tasks.h:313:20: error: 'rcu_task_stall_timeout' undeclared (first use in this function)
     313 |   rtst = READ_ONCE(rcu_task_stall_timeout);
         |                    ^~~~~~~~~~~~~~~~~~~~~~
   include/linux/compiler.h:285:17: note: in definition of macro '__READ_ONCE'
     285 |  union { typeof(x) __val; char __c[1]; } __u;   \
         |                 ^
   kernel/rcu/tasks.h:313:10: note: in expansion of macro 'READ_ONCE'
     313 |   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'
     987 |  BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
         |                                                   ^~
   include/linux/compiler.h:374:9: note: in definition of macro '__compiletime_assert'
     374 |   if (!(condition))     \
         |         ^~~~~~~~~
   include/linux/compiler.h:394:2: note: in expansion of macro '_compiletime_assert'
     394 |  _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
         |  ^~~~~~~~~~~~~~~~~~~
   include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
      39 | #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'
     987 |  BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
         |  ^~~~~~~~~~~~~~~~
   include/linux/kernel.h:987:20: note: in expansion of macro '__same_type'
     987 |  BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
         |                    ^~~~~~~~~~~
   include/linux/list.h:493:2: note: in expansion of macro 'container_of'
     493 |  container_of(ptr, type, member)
         |  ^~~~~~~~~~~~
   include/linux/list.h:504:2: note: in expansion of macro 'list_entry'
     504 |  list_entry((ptr)->next, type, member)
         |  ^~~~~~~~~~
   include/linux/list.h:688:13: note: in expansion of macro 'list_first_entry'
     688 |  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'
     319 |   list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
         |   ^~~~~~~~~~~~~~~~~~~~~~~~
   In file included from <command-line>:
   include/linux/compiler_types.h:129:35: error: 'struct task_struct' has no member named 'rcu_tasks_holdout_list'
     129 | #define __compiler_offsetof(a, b) __builtin_offsetof(a, b)
         |                                   ^~~~~~~~~~~~~~~~~~
   include/linux/stddef.h:17:32: note: in expansion of macro '__compiler_offsetof'
      17 | #define offsetof(TYPE, MEMBER) __compiler_offsetof(TYPE, MEMBER)
         |                                ^~~~~~~~~~~~~~~~~~~
   include/linux/kernel.h:990:21: note: in expansion of macro 'offsetof'
     990 |  ((type *)(__mptr - offsetof(type, member))); })
         |                     ^~~~~~~~
   include/linux/list.h:493:2: note: in expansion of macro 'container_of'
     493 |  container_of(ptr, type, member)
         |  ^~~~~~~~~~~~
   include/linux/list.h:504:2: note: in expansion of macro 'list_entry'
     504 |  list_entry((ptr)->next, type, member)
         |  ^~~~~~~~~~
   include/linux/list.h:688:13: note: in expansion of macro 'list_first_entry'
     688 |  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'
     319 |   list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
         |   ^~~~~~~~~~~~~~~~~~~~~~~~
   In file included from kernel/rcu/update.c:21:
   include/linux/list.h:537:18: error: 'struct task_struct' has no member named 'rcu_tasks_holdout_list'
     537 |  list_entry((pos)->member.next, typeof(*(pos)), member)
         |                  ^~
   include/linux/kernel.h:986:26: note: in definition of macro 'container_of'
     986 |  void *__mptr = (void *)(ptr);     \
         |                          ^~~
   include/linux/list.h:537:2: note: in expansion of macro 'list_entry'
     537 |  list_entry((pos)->member.next, typeof(*(pos)), member)
         |  ^~~~~~~~~~
   include/linux/list.h:689:7: note: in expansion of macro 'list_next_entry'
     689 |   n = list_next_entry(pos, member);   \
         |       ^~~~~~~~~~~~~~~
   kernel/rcu/tasks.h:319:3: note: in expansion of macro 'list_for_each_entry_safe'
     319 |   list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
         |   ^~~~~~~~~~~~~~~~~~~~~~~~
   In file included from include/linux/kernel.h:11,
                    from kernel/rcu/update.c:21:
   include/linux/list.h:537:18: error: 'struct task_struct' has no member named 'rcu_tasks_holdout_list'
     537 |  list_entry((pos)->member.next, typeof(*(pos)), member)
         |                  ^~
   include/linux/compiler.h:374:9: note: in definition of macro '__compiletime_assert'
     374 |   if (!(condition))     \
         |         ^~~~~~~~~
   include/linux/compiler.h:394:2: note: in expansion of macro '_compiletime_assert'
     394 |  _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
         |  ^~~~~~~~~~~~~~~~~~~
   include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
      39 | #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'
     987 |  BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
         |  ^~~~~~~~~~~~~~~~
   include/linux/kernel.h:987:20: note: in expansion of macro '__same_type'
     987 |  BUILD_BUG_ON_MSG(!__same_type(*(ptr), ((type *)0)->member) && \
         |                    ^~~~~~~~~~~
   include/linux/list.h:493:2: note: in expansion of macro 'container_of'
     493 |  container_of(ptr, type, member)
         |  ^~~~~~~~~~~~
   include/linux/list.h:537:2: note: in expansion of macro 'list_entry'

vim +/rcu_task_stall_timeout +313 kernel/rcu/tasks.h

6b80543d90000c Paul E. McKenney 2020-03-02  237  
61f7110d6b78f4 Paul E. McKenney 2020-03-02  238  /* Wait for one RCU-tasks grace period. */
61f7110d6b78f4 Paul E. McKenney 2020-03-02  239  static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)
6b80543d90000c Paul E. McKenney 2020-03-02  240  {
6b80543d90000c Paul E. McKenney 2020-03-02  241  	struct task_struct *g, *t;
6b80543d90000c Paul E. McKenney 2020-03-02  242  	unsigned long lastreport;
6b80543d90000c Paul E. McKenney 2020-03-02  243  	LIST_HEAD(rcu_tasks_holdouts);
6b80543d90000c Paul E. McKenney 2020-03-02  244  	int fract;
6b80543d90000c Paul E. McKenney 2020-03-02  245  
6b80543d90000c Paul E. McKenney 2020-03-02  246  	/*
61f7110d6b78f4 Paul E. McKenney 2020-03-02  247  	 * Wait for all pre-existing t->on_rq and t->nvcsw transitions
61f7110d6b78f4 Paul E. McKenney 2020-03-02  248  	 * to complete.  Invoking synchronize_rcu() suffices because all
61f7110d6b78f4 Paul E. McKenney 2020-03-02  249  	 * these transitions occur with interrupts disabled.  Without this
61f7110d6b78f4 Paul E. McKenney 2020-03-02  250  	 * synchronize_rcu(), a read-side critical section that started
61f7110d6b78f4 Paul E. McKenney 2020-03-02  251  	 * before the grace period might be incorrectly seen as having
61f7110d6b78f4 Paul E. McKenney 2020-03-02  252  	 * started after the grace period.
6b80543d90000c Paul E. McKenney 2020-03-02  253  	 *
61f7110d6b78f4 Paul E. McKenney 2020-03-02  254  	 * This synchronize_rcu() also dispenses with the need for a
61f7110d6b78f4 Paul E. McKenney 2020-03-02  255  	 * memory barrier on the first store to t->rcu_tasks_holdout,
61f7110d6b78f4 Paul E. McKenney 2020-03-02  256  	 * as it forces the store to happen after the beginning of the
61f7110d6b78f4 Paul E. McKenney 2020-03-02  257  	 * grace period.
6b80543d90000c Paul E. McKenney 2020-03-02  258  	 */
6b80543d90000c Paul E. McKenney 2020-03-02  259  	synchronize_rcu();
6b80543d90000c Paul E. McKenney 2020-03-02  260  
6b80543d90000c Paul E. McKenney 2020-03-02  261  	/*
61f7110d6b78f4 Paul E. McKenney 2020-03-02  262  	 * There were callbacks, so we need to wait for an RCU-tasks
61f7110d6b78f4 Paul E. McKenney 2020-03-02  263  	 * grace period.  Start off by scanning the task list for tasks
61f7110d6b78f4 Paul E. McKenney 2020-03-02  264  	 * that are not already voluntarily blocked.  Mark these tasks
61f7110d6b78f4 Paul E. McKenney 2020-03-02  265  	 * and make a list of them in rcu_tasks_holdouts.
6b80543d90000c Paul E. McKenney 2020-03-02  266  	 */
6b80543d90000c Paul E. McKenney 2020-03-02  267  	rcu_read_lock();
6b80543d90000c Paul E. McKenney 2020-03-02  268  	for_each_process_thread(g, t) {
61f7110d6b78f4 Paul E. McKenney 2020-03-02  269  		if (t != current && READ_ONCE(t->on_rq) && !is_idle_task(t)) {
6b80543d90000c Paul E. McKenney 2020-03-02  270  			get_task_struct(t);
6b80543d90000c Paul E. McKenney 2020-03-02  271  			t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw);
6b80543d90000c Paul E. McKenney 2020-03-02  272  			WRITE_ONCE(t->rcu_tasks_holdout, true);
6b80543d90000c Paul E. McKenney 2020-03-02 @273  			list_add(&t->rcu_tasks_holdout_list,
6b80543d90000c Paul E. McKenney 2020-03-02  274  				 &rcu_tasks_holdouts);
6b80543d90000c Paul E. McKenney 2020-03-02  275  		}
6b80543d90000c Paul E. McKenney 2020-03-02  276  	}
6b80543d90000c Paul E. McKenney 2020-03-02  277  	rcu_read_unlock();
6b80543d90000c Paul E. McKenney 2020-03-02  278  
6b80543d90000c Paul E. McKenney 2020-03-02  279  	/*
61f7110d6b78f4 Paul E. McKenney 2020-03-02  280  	 * Wait for tasks that are in the process of exiting.  This
61f7110d6b78f4 Paul E. McKenney 2020-03-02  281  	 * does only part of the job, ensuring that all tasks that were
61f7110d6b78f4 Paul E. McKenney 2020-03-02  282  	 * previously exiting reach the point where they have disabled
61f7110d6b78f4 Paul E. McKenney 2020-03-02  283  	 * preemption, allowing the later synchronize_rcu() to finish
61f7110d6b78f4 Paul E. McKenney 2020-03-02  284  	 * the job.
6b80543d90000c Paul E. McKenney 2020-03-02  285  	 */
6b80543d90000c Paul E. McKenney 2020-03-02  286  	synchronize_srcu(&tasks_rcu_exit_srcu);
6b80543d90000c Paul E. McKenney 2020-03-02  287  
6b80543d90000c Paul E. McKenney 2020-03-02  288  	/*
61f7110d6b78f4 Paul E. McKenney 2020-03-02  289  	 * Each pass through the following loop scans the list of holdout
61f7110d6b78f4 Paul E. McKenney 2020-03-02  290  	 * tasks, removing any that are no longer holdouts.  When the list
61f7110d6b78f4 Paul E. McKenney 2020-03-02  291  	 * is empty, we are done.
6b80543d90000c Paul E. McKenney 2020-03-02  292  	 */
6b80543d90000c Paul E. McKenney 2020-03-02  293  	lastreport = jiffies;
6b80543d90000c Paul E. McKenney 2020-03-02  294  
61f7110d6b78f4 Paul E. McKenney 2020-03-02  295  	/* Start off with HZ/10 wait and slowly back off to 1 HZ wait. */
6b80543d90000c Paul E. McKenney 2020-03-02  296  	fract = 10;
6b80543d90000c Paul E. McKenney 2020-03-02  297  
6b80543d90000c Paul E. McKenney 2020-03-02  298  	for (;;) {
6b80543d90000c Paul E. McKenney 2020-03-02  299  		bool firstreport;
6b80543d90000c Paul E. McKenney 2020-03-02  300  		bool needreport;
6b80543d90000c Paul E. McKenney 2020-03-02  301  		int rtst;
6b80543d90000c Paul E. McKenney 2020-03-02  302  		struct task_struct *t1;
6b80543d90000c Paul E. McKenney 2020-03-02  303  
6b80543d90000c Paul E. McKenney 2020-03-02  304  		if (list_empty(&rcu_tasks_holdouts))
6b80543d90000c Paul E. McKenney 2020-03-02  305  			break;
6b80543d90000c Paul E. McKenney 2020-03-02  306  
6b80543d90000c Paul E. McKenney 2020-03-02  307  		/* Slowly back off waiting for holdouts */
6b80543d90000c Paul E. McKenney 2020-03-02  308  		schedule_timeout_interruptible(HZ/fract);
6b80543d90000c Paul E. McKenney 2020-03-02  309  
6b80543d90000c Paul E. McKenney 2020-03-02  310  		if (fract > 1)
6b80543d90000c Paul E. McKenney 2020-03-02  311  			fract--;
6b80543d90000c Paul E. McKenney 2020-03-02  312  
6b80543d90000c Paul E. McKenney 2020-03-02 @313  		rtst = READ_ONCE(rcu_task_stall_timeout);
61f7110d6b78f4 Paul E. McKenney 2020-03-02  314  		needreport = rtst > 0 && time_after(jiffies, lastreport + rtst);
6b80543d90000c Paul E. McKenney 2020-03-02  315  		if (needreport)
6b80543d90000c Paul E. McKenney 2020-03-02  316  			lastreport = jiffies;
6b80543d90000c Paul E. McKenney 2020-03-02  317  		firstreport = true;
6b80543d90000c Paul E. McKenney 2020-03-02  318  		WARN_ON(signal_pending(current));
6b80543d90000c Paul E. McKenney 2020-03-02  319  		list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
6b80543d90000c Paul E. McKenney 2020-03-02  320  					 rcu_tasks_holdout_list) {
6b80543d90000c Paul E. McKenney 2020-03-02  321  			check_holdout_task(t, needreport, &firstreport);
6b80543d90000c Paul E. McKenney 2020-03-02  322  			cond_resched();
6b80543d90000c Paul E. McKenney 2020-03-02  323  		}
6b80543d90000c Paul E. McKenney 2020-03-02  324  	}
6b80543d90000c Paul E. McKenney 2020-03-02  325  
6b80543d90000c Paul E. McKenney 2020-03-02  326  	/*
61f7110d6b78f4 Paul E. McKenney 2020-03-02  327  	 * Because ->on_rq and ->nvcsw are not guaranteed to have a full
61f7110d6b78f4 Paul E. McKenney 2020-03-02  328  	 * memory barriers prior to them in the schedule() path, memory
61f7110d6b78f4 Paul E. McKenney 2020-03-02  329  	 * reordering on other CPUs could cause their RCU-tasks read-side
61f7110d6b78f4 Paul E. McKenney 2020-03-02  330  	 * critical sections to extend past the end of the grace period.
61f7110d6b78f4 Paul E. McKenney 2020-03-02  331  	 * However, because these ->nvcsw updates are carried out with
61f7110d6b78f4 Paul E. McKenney 2020-03-02  332  	 * interrupts disabled, we can use synchronize_rcu() to force the
61f7110d6b78f4 Paul E. McKenney 2020-03-02  333  	 * needed ordering on all such CPUs.
6b80543d90000c Paul E. McKenney 2020-03-02  334  	 *
61f7110d6b78f4 Paul E. McKenney 2020-03-02  335  	 * This synchronize_rcu() also confines all ->rcu_tasks_holdout
61f7110d6b78f4 Paul E. McKenney 2020-03-02  336  	 * accesses to be within the grace period, avoiding the need for
61f7110d6b78f4 Paul E. McKenney 2020-03-02  337  	 * memory barriers for ->rcu_tasks_holdout accesses.
6b80543d90000c Paul E. McKenney 2020-03-02  338  	 *
61f7110d6b78f4 Paul E. McKenney 2020-03-02  339  	 * In addition, this synchronize_rcu() waits for exiting tasks
61f7110d6b78f4 Paul E. McKenney 2020-03-02  340  	 * to complete their final preempt_disable() region of execution,
61f7110d6b78f4 Paul E. McKenney 2020-03-02  341  	 * cleaning up after the synchronize_srcu() above.
6b80543d90000c Paul E. McKenney 2020-03-02  342  	 */
6b80543d90000c Paul E. McKenney 2020-03-02  343  	synchronize_rcu();
61f7110d6b78f4 Paul E. McKenney 2020-03-02  344  }
6b80543d90000c Paul E. McKenney 2020-03-02  345  

:::::: The code at line 313 was first introduced by commit
:::::: 6b80543d90000c684123b05f075ac1433d99fa85 tasks-rcu: Move Tasks RCU to its own file

:::::: TO: Paul E. McKenney <paulmck@...nel.org>
:::::: CC: Paul E. McKenney <paulmck@...nel.org>

---
0-DAY CI Kernel Test Service, Intel Corporation
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