From: Peter Zijlstra <peterz@infradead.org>
To: paulmck@linux.vnet.ibm.com
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca,
josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de,
rostedt@goodmis.org, Valdis.Kletnieks@vt.edu,
dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com,
fweisbec@gmail.com, patches@linaro.org,
Hugh Dickins <hughd@google.com>
Subject: Re: [PATCH tip/core/rcu 3/4] rcu: stop spurious warnings from synchronize_sched_expedited
Date: Tue, 21 Feb 2012 19:57:03 +0100 [thread overview]
Message-ID: <1329850623.2293.419.camel@twins> (raw)
In-Reply-To: <20120221182804.GK2375@linux.vnet.ibm.com>
On Tue, 2012-02-21 at 10:28 -0800, Paul E. McKenney wrote:
> On Tue, Feb 21, 2012 at 07:00:17PM +0100, Peter Zijlstra wrote:
> > On Tue, 2012-02-21 at 09:58 -0800, Paul E. McKenney wrote:
> > > From: Hugh Dickins <hughd@google.com>
> > >
> > > synchronize_sched_expedited() is spamming CONFIG_DEBUG_PREEMPT=y
> > > users with an unintended warning from the cpu_is_offline() check:
> > > use raw_smp_processor_id() instead of smp_processor_id() there.
> >
> > This fails to mention why it makes sense to test a random cpu for
> > offline-ness..
>
> The check was already there, Hugh simply fixed it to use raw_. The check
> itself was added in c0d6d01bf (Check for illegal use of RCU from offlined
> CPUs). The purpose is to catch improper use of RCU from CPU_DYING
> notifiers and on the path from the CPU_DYING notifiers to the idle loop.
Then I think this patch wants to add a comment explaining this. Because
cpu_offline(raw_smp_processor_id()) looks really rather suspicious.
next prev parent reply other threads:[~2012-02-21 18:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-21 17:58 [PATCH tip/core/rcu 0/4] Additional RCU commits for 3.4 Paul E. McKenney
2012-02-21 17:58 ` [PATCH tip/core/rcu 1/4] rcu: Eliminate softirq-mediated RCU_FAST_NO_HZ idle-entry loop Paul E. McKenney
2012-02-21 17:58 ` [PATCH tip/core/rcu 2/4] rcu: Hold off RCU_FAST_NO_HZ after timer posted Paul E. McKenney
2012-02-21 17:58 ` [PATCH tip/core/rcu 3/4] rcu: stop spurious warnings from synchronize_sched_expedited Paul E. McKenney
2012-02-21 18:00 ` Peter Zijlstra
2012-02-21 18:28 ` Paul E. McKenney
2012-02-21 18:57 ` Peter Zijlstra [this message]
2012-02-21 23:30 ` Paul E. McKenney
2012-02-21 17:58 ` [PATCH tip/core/rcu 3/4] rcu: Stop " Paul E. McKenney
2012-02-21 17:58 ` [PATCH tip/core/rcu 4/4] rcu: Fixes to rcutorture error handling and cleanup Paul E. McKenney
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