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From: Peter Zijlstra <peterz@infradead.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Will Deacon <will@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Paul E . McKenney" <paulmck@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Josh Triplett <josh@joshtriplett.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	rcu@vger.kernel.org
Subject: Re: [PATCH 3/8] srcu: Use local_lock() for per-CPU struct srcu_data access
Date: Wed, 20 May 2020 12:24:07 +0200
Message-ID: <20200520102407.GF317569@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200519201912.1564477-4-bigeasy@linutronix.de>

On Tue, May 19, 2020 at 10:19:07PM +0200, Sebastian Andrzej Siewior wrote:

> diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
> index 0c71505f0e19c..8d2b5f75145d7 100644
> --- a/kernel/rcu/srcutree.c
> +++ b/kernel/rcu/srcutree.c
> @@ -25,6 +25,7 @@
>  #include <linux/delay.h>
>  #include <linux/module.h>
>  #include <linux/srcu.h>
> +#include <linux/locallock.h>
>  
>  #include "rcu.h"
>  #include "rcu_segcblist.h"
> @@ -735,6 +736,7 @@ static void srcu_flip(struct srcu_struct *ssp)
>  	smp_mb(); /* D */  /* Pairs with C. */
>  }
>  
> +static DEFINE_LOCAL_LOCK(sda_lock);
>  /*
>   * If SRCU is likely idle, return true, otherwise return false.
>   *
> @@ -765,13 +767,13 @@ static bool srcu_might_be_idle(struct srcu_struct *ssp)
>  	unsigned long tlast;
>  
>  	/* If the local srcu_data structure has callbacks, not idle.  */
> -	local_irq_save(flags);
> +	local_lock_irqsave(sda_lock, flags);
>  	sdp = this_cpu_ptr(ssp->sda);
>  	if (rcu_segcblist_pend_cbs(&sdp->srcu_cblist)) {
> -		local_irq_restore(flags);
> +		local_unlock_irqrestore(sda_lock, flags);
>  		return false; /* Callbacks already present, so not idle. */
>  	}
> -	local_irq_restore(flags);
> +	local_unlock_irqrestore(sda_lock, flags);

Would it perhaps make sense to stick the local_lock in struct srcu_data ?

  reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20200519201912.1564477-1-bigeasy@linutronix.de>
2020-05-19 20:19 ` Sebastian Andrzej Siewior
2020-05-20 10:24   ` Peter Zijlstra [this message]
2020-05-20 12:06     ` Sebastian Andrzej Siewior
2020-05-20 13:27       ` Peter Zijlstra
2020-05-20 17:42       ` Joel Fernandes
2020-05-20 18:28         ` Sebastian Andrzej Siewior
2020-05-20 18:35           ` Peter Zijlstra
2020-05-20 18:44             ` Joel Fernandes
2020-05-20 18:50               ` Uladzislau Rezki
2020-05-20 18:59           ` Joel Fernandes
2020-05-20 18:43       ` Paul E. McKenney
2020-05-22 15:12         ` Sebastian Andrzej Siewior
2020-05-22 17:39           ` Paul E. McKenney
2020-05-23 15:08             ` Sebastian Andrzej Siewior
2020-05-23 16:59               ` Paul E. McKenney
2020-05-24 19:03               ` Sebastian Andrzej Siewior
2020-05-25  3:27                 ` Paul E. McKenney
2020-05-26 13:41                   ` [PATCH] srcu: Avoid local_irq_save() before acquiring spinlock_t Sebastian Andrzej Siewior
2020-05-26 16:16                     ` Paul E. McKenney
2020-05-26 16:31                       ` Sebastian Andrzej Siewior

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