[linux-next:master 4056/14131] kernel//rcu/tasks.h:890:6: warning: no previous prototype for function 'synchronize_rcu_tasks_trace'

[linux-next:master 4056/14131] kernel//rcu/tasks.h:890:6: warning: no previous prototype for function 'synchronize_rcu_tasks_trace'

[kbuild test robot]

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tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   e7b08814b16b80a0bf76eeca16317f8c2ed23b8c
commit: c1a76c0b6abac4e7eb49b5c24a0829f47b70769d [4056/14131] rcutorture: Add torture tests for RCU Tasks Trace
config: x86_64-randconfig-a015-20200529 (attached as .config)
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 2d068e534f1671459e1b135852c1b3c10502e929)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install x86_64 cross compiling tool for clang build
        # apt-get install binutils-x86-64-linux-gnu
        git checkout c1a76c0b6abac4e7eb49b5c24a0829f47b70769d
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 

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

All warnings (new ones prefixed by >>, old ones prefixed by <<):

In file included from kernel//rcu/update.c:588:
kernel//rcu/tasks.h:329:6: warning: no previous prototype for function 'rcu_tasks_postscan' [-Wmissing-prototypes]
void rcu_tasks_postscan(void)
^
kernel//rcu/tasks.h:329:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
void rcu_tasks_postscan(void)
^
static
>> kernel//rcu/tasks.h:625:6: warning: no previous prototype for function 'rcu_read_unlock_trace_special' [-Wmissing-prototypes]
void rcu_read_unlock_trace_special(struct task_struct *t)
^
kernel//rcu/tasks.h:625:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
void rcu_read_unlock_trace_special(struct task_struct *t)
^
static
kernel//rcu/tasks.h:740:42: error: use of undeclared identifier 'rcu_tasks_trace'
if (task_curr(t) && time_after(jiffies, rcu_tasks_trace.gp_start + rcu_task_ipi_delay)) {
^
kernel//rcu/tasks.h:740:69: error: use of undeclared identifier 'rcu_task_ipi_delay'
if (task_curr(t) && time_after(jiffies, rcu_tasks_trace.gp_start + rcu_task_ipi_delay)) {
^
kernel//rcu/tasks.h:740:42: error: use of undeclared identifier 'rcu_tasks_trace'
if (task_curr(t) && time_after(jiffies, rcu_tasks_trace.gp_start + rcu_task_ipi_delay)) {
^
kernel//rcu/tasks.h:740:69: error: use of undeclared identifier 'rcu_task_ipi_delay'
if (task_curr(t) && time_after(jiffies, rcu_tasks_trace.gp_start + rcu_task_ipi_delay)) {
^
>> kernel//rcu/tasks.h:890:6: warning: no previous prototype for function 'synchronize_rcu_tasks_trace' [-Wmissing-prototypes]
void synchronize_rcu_tasks_trace(void)
^
kernel//rcu/tasks.h:890:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
void synchronize_rcu_tasks_trace(void)
^
static
>> kernel//rcu/tasks.h:903:6: warning: no previous prototype for function 'rcu_barrier_tasks_trace' [-Wmissing-prototypes]
void rcu_barrier_tasks_trace(void)
^
kernel//rcu/tasks.h:903:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
void rcu_barrier_tasks_trace(void)
^
static
4 warnings and 4 errors generated.

vim +/synchronize_rcu_tasks_trace +890 kernel//rcu/tasks.h

d5f177d35c2442 Paul E. McKenney 2020-03-09  871  
d5f177d35c2442 Paul E. McKenney 2020-03-09  872  /**
d5f177d35c2442 Paul E. McKenney 2020-03-09  873   * synchronize_rcu_tasks_trace - wait for a trace rcu-tasks grace period
d5f177d35c2442 Paul E. McKenney 2020-03-09  874   *
d5f177d35c2442 Paul E. McKenney 2020-03-09  875   * Control will return to the caller some time after a trace rcu-tasks
d5f177d35c2442 Paul E. McKenney 2020-03-09  876   * grace period has elapsed, in other words after all currently
d5f177d35c2442 Paul E. McKenney 2020-03-09  877   * executing rcu-tasks read-side critical sections have elapsed.  These
d5f177d35c2442 Paul E. McKenney 2020-03-09  878   * read-side critical sections are delimited by calls to schedule(),
d5f177d35c2442 Paul E. McKenney 2020-03-09  879   * cond_resched_tasks_rcu_qs(), userspace execution, and (in theory,
d5f177d35c2442 Paul E. McKenney 2020-03-09  880   * anyway) cond_resched().
d5f177d35c2442 Paul E. McKenney 2020-03-09  881   *
d5f177d35c2442 Paul E. McKenney 2020-03-09  882   * This is a very specialized primitive, intended only for a few uses in
d5f177d35c2442 Paul E. McKenney 2020-03-09  883   * tracing and other situations requiring manipulation of function preambles
d5f177d35c2442 Paul E. McKenney 2020-03-09  884   * and profiling hooks.  The synchronize_rcu_tasks_trace() function is not
d5f177d35c2442 Paul E. McKenney 2020-03-09  885   * (yet) intended for heavy use from multiple CPUs.
d5f177d35c2442 Paul E. McKenney 2020-03-09  886   *
d5f177d35c2442 Paul E. McKenney 2020-03-09  887   * See the description of synchronize_rcu() for more detailed information
d5f177d35c2442 Paul E. McKenney 2020-03-09  888   * on memory ordering guarantees.
d5f177d35c2442 Paul E. McKenney 2020-03-09  889   */
d5f177d35c2442 Paul E. McKenney 2020-03-09 @890  void synchronize_rcu_tasks_trace(void)
d5f177d35c2442 Paul E. McKenney 2020-03-09  891  {
d5f177d35c2442 Paul E. McKenney 2020-03-09  892  	RCU_LOCKDEP_WARN(lock_is_held(&rcu_trace_lock_map), "Illegal synchronize_rcu_tasks_trace() in RCU Tasks Trace read-side critical section");
d5f177d35c2442 Paul E. McKenney 2020-03-09  893  	synchronize_rcu_tasks_generic(&rcu_tasks_trace);
d5f177d35c2442 Paul E. McKenney 2020-03-09  894  }
d5f177d35c2442 Paul E. McKenney 2020-03-09  895  EXPORT_SYMBOL_GPL(synchronize_rcu_tasks_trace);
d5f177d35c2442 Paul E. McKenney 2020-03-09  896  
d5f177d35c2442 Paul E. McKenney 2020-03-09  897  /**
d5f177d35c2442 Paul E. McKenney 2020-03-09  898   * rcu_barrier_tasks_trace - Wait for in-flight call_rcu_tasks_trace() callbacks.
d5f177d35c2442 Paul E. McKenney 2020-03-09  899   *
d5f177d35c2442 Paul E. McKenney 2020-03-09  900   * Although the current implementation is guaranteed to wait, it is not
d5f177d35c2442 Paul E. McKenney 2020-03-09  901   * obligated to, for example, if there are no pending callbacks.
d5f177d35c2442 Paul E. McKenney 2020-03-09  902   */
d5f177d35c2442 Paul E. McKenney 2020-03-09 @903  void rcu_barrier_tasks_trace(void)
d5f177d35c2442 Paul E. McKenney 2020-03-09  904  {
d5f177d35c2442 Paul E. McKenney 2020-03-09  905  	/* There is only one callback queue, so this is easy.  ;-) */
d5f177d35c2442 Paul E. McKenney 2020-03-09  906  	synchronize_rcu_tasks_trace();
d5f177d35c2442 Paul E. McKenney 2020-03-09  907  }
d5f177d35c2442 Paul E. McKenney 2020-03-09  908  EXPORT_SYMBOL_GPL(rcu_barrier_tasks_trace);
d5f177d35c2442 Paul E. McKenney 2020-03-09  909  

:::::: The code at line 890 was first introduced by commit
:::::: d5f177d35c24429c87db2567d20563fc16f7e8f6 rcu-tasks: Add an RCU Tasks Trace to simplify protection of tracing hooks

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

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

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