From: Dave Jones <davej@redhat.com>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: cl@linux.com, linux-kernel@vger.kernel.org, mingo@kernel.org,
tj@kernel.org, grygorii.strashko@ti.com, peterz@infradead.org
Subject: Re: How do I increment a per-CPU variable without warning?
Date: Tue, 15 Apr 2014 18:29:51 -0400 [thread overview]
Message-ID: <20140415222951.GA742@redhat.com> (raw)
In-Reply-To: <20140415221755.GA27188@linux.vnet.ibm.com>
On Tue, Apr 15, 2014 at 03:17:55PM -0700, Paul E. McKenney wrote:
> My current admittedly crude workaround is as follows:
>
> static inline bool rcu_should_resched(void)
> {
> int t;
>
> #ifdef CONFIG_DEBUG_PREEMPT
> preempt_disable();
> #endif /* #ifdef CONFIG_DEBUG_PREEMPT */
> t = __this_cpu_read(rcu_cond_resched_count) + 1;
> if (t < RCU_COND_RESCHED_LIM) {
> __this_cpu_write(rcu_cond_resched_count, t);
> #ifdef CONFIG_DEBUG_PREEMPT
> preempt_enable();
> #endif /* #ifdef CONFIG_DEBUG_PREEMPT */
> return false;
> }
> #ifdef CONFIG_DEBUG_PREEMPT
> preempt_enable();
> #endif /* #ifdef CONFIG_DEBUG_PREEMPT */
> return true;
> }
Won't using DEBUG_PREEMPT instead of just CONFIG_PREEMPT here make this
silently do the wrong thing if preemption is enabled, but debugging isn't ?
I'm not seeing why you need the ifdefs at all, unless the implied
barrier() is a problem ?
Dave
next prev parent reply other threads:[~2014-04-15 22:32 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-15 22:17 How do I increment a per-CPU variable without warning? Paul E. McKenney
2014-04-15 22:29 ` Dave Jones [this message]
2014-04-15 22:47 ` Paul E. McKenney
2014-04-16 3:54 ` Paul E. McKenney
2014-04-16 5:21 ` Peter Zijlstra
2014-04-16 13:03 ` Paul E. McKenney
2014-04-16 15:12 ` Christoph Lameter
2014-04-16 5:19 ` Peter Zijlstra
2014-04-16 15:08 ` Christoph Lameter
2014-04-16 16:06 ` Paul E. McKenney
2014-04-16 17:12 ` Paul E. McKenney
2014-04-16 18:29 ` Christoph Lameter
2014-04-16 18:47 ` Paul E. McKenney
2014-04-17 17:36 ` Christoph Lameter
2014-04-17 17:46 ` Paul E. McKenney
2014-04-17 17:53 ` Christoph Lameter
2014-04-17 18:21 ` Paul E. McKenney
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