linux-kernel - Re: [RFC PATCH 08/14] rcu: Convert RCU gp kthreads into kthread worker API

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Message-ID: <20150728173744.GE5322@mtj.duckdns.org>
Date:	Tue, 28 Jul 2015 13:37:44 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Petr Mladek <pmladek@...e.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josh@...htriplett.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>, Borislav Petkov <bp@...e.de>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	Vlastimil Babka <vbabka@...e.cz>,
	live-patching@...r.kernel.org, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 08/14] rcu: Convert RCU gp kthreads into kthread
 worker API

On Tue, Jul 28, 2015 at 04:39:25PM +0200, Petr Mladek wrote:
...
> -static int __noreturn rcu_gp_kthread(void *arg)
> +static void rcu_gp_kthread_func(struct kthread_work *work)
>  {
>  	int fqs_state;
>  	int gf;
>  	unsigned long j;
>  	int ret;
> -	struct rcu_state *rsp = arg;
> +	struct rcu_state *rsp = container_of(work, struct rcu_state, gp_work);
>  	struct rcu_node *rnp = rcu_get_root(rsp);
>  
> -	rcu_bind_gp_kthread();
> +	/* Handle grace-period start. */
>  	for (;;) {
> +		trace_rcu_grace_period(rsp->name,
> +				       READ_ONCE(rsp->gpnum),
> +				       TPS("reqwait"));
> +		rsp->gp_state = RCU_GP_WAIT_GPS;
> +		wait_event_interruptible(rsp->gp_wq,
> +					 READ_ONCE(rsp->gp_flags) &
> +					 RCU_GP_FLAG_INIT);

Same here.  Why not convert the waker into a queueing event?

> +		/* Locking provides needed memory barrier. */
> +		if (rcu_gp_init(rsp))
> +			break;
> +		cond_resched_rcu_qs();
> +		WRITE_ONCE(rsp->gp_activity, jiffies);
> +		WARN_ON(signal_pending(current));
> +		trace_rcu_grace_period(rsp->name,
> +				       READ_ONCE(rsp->gpnum),
> +				       TPS("reqwaitsig"));
> +	}

Thanks.

-- 
tejun
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