linux-kernel - [paulmck-rcu:locktorture.2023.08.17a 14/20] kernel/rcu/tree.c:4100:6: warning: no previous declaration for 'rcu_barrier

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Message-ID: <202308180853.brWVZKoo-lkp@intel.com>
Date:   Fri, 18 Aug 2023 09:02:35 +0800
From:   kernel test robot <lkp@...el.com>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: [paulmck-rcu:locktorture.2023.08.17a 14/20]
 kernel/rcu/tree.c:4100:6: warning: no previous declaration for
 'rcu_barrier_throttled'

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git locktorture.2023.08.17a
head:   ccd7c62460a1ca6a8fb800de0d50d973ba62dcb8
commit: 365332de5f7bd1ab448ad4a6bd73a4fc8f1cc8ec [14/20] rcu: Add sysfs to provide throttled access to rcu_barrier()
config: x86_64-randconfig-x071-20230818 (https://download.01.org/0day-ci/archive/20230818/202308180853.brWVZKoo-lkp@intel.com/config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
reproduce: (https://download.01.org/0day-ci/archive/20230818/202308180853.brWVZKoo-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202308180853.brWVZKoo-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> kernel/rcu/tree.c:4100:6: warning: no previous declaration for 'rcu_barrier_throttled' [-Wmissing-declarations]
    void rcu_barrier_throttled(void)
         ^~~~~~~~~~~~~~~~~~~~~


vim +/rcu_barrier_throttled +4100 kernel/rcu/tree.c

  4083	
  4084	/**
  4085	 * rcu_barrier_throttled - Do rcu_barrier(), but limit to one per second
  4086	 *
  4087	 * This can be thought of as guard rails around rcu_barrier() that
  4088	 * permits unrestricted userspace use, at least assuming the hardware's
  4089	 * try_cmpxchg() is robust.  There will be at most one call per second to
  4090	 * rcu_barrier() system-wide from use of this function, which means that
  4091	 * callers might needlessly wait a second or three.
  4092	 *
  4093	 * This is intended for use by test suites to avoid OOM by flushing RCU
  4094	 * callbacks from the previous test before starting the next.  See the
  4095	 * rcutree.do_rcu_barrier module parameter for more information.
  4096	 *
  4097	 * Why not simply make rcu_barrier() more scalable?  That might be the
  4098	 * eventual endpoint, but let's keep it simple for the time being.
  4099	 */
> 4100	void rcu_barrier_throttled(void)
  4101	{
  4102		unsigned long j = jiffies;
  4103		unsigned long old = READ_ONCE(rcu_barrier_last_throttle);
  4104		unsigned long s = rcu_seq_snap(&rcu_state.barrier_sequence);
  4105	
  4106		while (time_after(old + HZ, j) || !try_cmpxchg(&rcu_barrier_last_throttle, &old, j + HZ)) {
  4107			schedule_timeout_idle(HZ);
  4108			if (rcu_seq_done(&rcu_state.barrier_sequence, s))
  4109				return;
  4110			old = READ_ONCE(rcu_barrier_last_throttle);
  4111		}
  4112		rcu_barrier();
  4113	}
  4114	

-- 
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https://github.com/intel/lkp-tests/wiki