Re: [rcu:rcu/next 78/83] kernel/rcu/tasks.h:740:8: error: type defaults to 'int' in declaration of 'DEFINE_IRQ_WORK'

["Paul E. McKenney" <paulmck@kernel.org>]

On Mon, Mar 23, 2020 at 01:26:49PM +0800, kbuild test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/next
> head:   72f26c3be409e0ccd52a48e7f5ffbdbb5cd0a960
> commit: f7f9f5b97a87a31d90fe254f6e685b67e0b378a9 [78/83] rcu-tasks: Allow rcu_read_unlock_trace() under scheduler locks
> config: m68k-allmodconfig (attached as .config)
> compiler: m68k-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 f7f9f5b97a87a31d90fe254f6e685b67e0b378a9
>         # save the attached .config to linux build tree
>         GCC_VERSION=9.2.0 make.cross ARCH=m68k 
> 
> If you fix the issue, kindly add following tag
> Reported-by: kbuild test robot <lkp@intel.com>

I believe I have this fixed via a #include of linux/irq_work.h, which I
will fold into the original patch.

Thank you for finding this!

							Thanx, Paul

> All error/warnings (new ones prefixed by >>):
> 
>    In file included from kernel/rcu/update.c:562:
> >> kernel/rcu/tasks.h:736:39: warning: 'struct irq_work' declared inside parameter list will not be visible outside of this definition or declaration
>      736 | static void rcu_read_unlock_iw(struct irq_work *iwp)
>          |                                       ^~~~~~~~
> >> kernel/rcu/tasks.h:740:8: error: type defaults to 'int' in declaration of 'DEFINE_IRQ_WORK' [-Werror=implicit-int]
>      740 | static DEFINE_IRQ_WORK(rcu_tasks_trace_iw, rcu_read_unlock_iw);
>          |        ^~~~~~~~~~~~~~~
> >> kernel/rcu/tasks.h:740:1: warning: parameter names (without types) in function declaration
>      740 | static DEFINE_IRQ_WORK(rcu_tasks_trace_iw, rcu_read_unlock_iw);
>          | ^~~~~~
>    kernel/rcu/tasks.h: In function 'rcu_read_unlock_trace_special':
> >> kernel/rcu/tasks.h:751:3: error: implicit declaration of function 'irq_work_queue'; did you mean 'drain_workqueue'? [-Werror=implicit-function-declaration]
>      751 |   irq_work_queue(&rcu_tasks_trace_iw);
>          |   ^~~~~~~~~~~~~~
>          |   drain_workqueue
> >> kernel/rcu/tasks.h:751:19: error: 'rcu_tasks_trace_iw' undeclared (first use in this function); did you mean 'rcu_tasks_trace_qs'?
>      751 |   irq_work_queue(&rcu_tasks_trace_iw);
>          |                   ^~~~~~~~~~~~~~~~~~
>          |                   rcu_tasks_trace_qs
>    kernel/rcu/tasks.h:751:19: note: each undeclared identifier is reported only once for each function it appears in
>    kernel/rcu/update.c: At top level:
>    kernel/rcu/tasks.h:740:8: warning: 'DEFINE_IRQ_WORK' declared 'static' but never defined [-Wunused-function]
>      740 | static DEFINE_IRQ_WORK(rcu_tasks_trace_iw, rcu_read_unlock_iw);
>          |        ^~~~~~~~~~~~~~~
>    kernel/rcu/tasks.h:736:13: warning: 'rcu_read_unlock_iw' defined but not used [-Wunused-function]
>      736 | static void rcu_read_unlock_iw(struct irq_work *iwp)
>          |             ^~~~~~~~~~~~~~~~~~
>    cc1: some warnings being treated as errors
> 
> vim +740 kernel/rcu/tasks.h
> 
>    727	
>    728	void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func);
>    729	DEFINE_RCU_TASKS(rcu_tasks_trace, rcu_tasks_wait_gp, call_rcu_tasks_trace,
>    730			 "RCU Tasks Trace");
>    731	
>    732	/*
>    733	 * This irq_work handler allows rcu_read_unlock_trace() to be invoked
>    734	 * while the scheduler locks are held.
>    735	 */
>  > 736	static void rcu_read_unlock_iw(struct irq_work *iwp)
>    737	{
>    738		wake_up(&trc_wait);
>    739	}
>  > 740	static DEFINE_IRQ_WORK(rcu_tasks_trace_iw, rcu_read_unlock_iw);
>    741	
>    742	/* If we are the last reader, wake up the grace-period kthread. */
>    743	void rcu_read_unlock_trace_special(struct task_struct *t, int nesting)
>    744	{
>    745		if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) &&
>    746		    t->trc_reader_special.b.need_mb)
>    747			smp_mb(); // Pairs with update-side barriers.
>    748		WRITE_ONCE(t->trc_reader_nesting, nesting);
>    749		WRITE_ONCE(t->trc_reader_special.b.need_qs, false);
>    750		if (atomic_dec_and_test(&trc_n_readers_need_end))
>  > 751			irq_work_queue(&rcu_tasks_trace_iw);
>    752	}
>    753	EXPORT_SYMBOL_GPL(rcu_read_unlock_trace_special);
>    754	
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
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