From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Dave Hansen <dave@sr71.net>
Cc: sedat.dilek@gmail.com, "Rafael J. Wysocki" <rjw@rjwysocki.net>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
linux-next <linux-next@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Kristen Carlson Accardi <kristen@linux.intel.com>,
"H. Peter Anvin" <hpa@linux.intel.com>,
Rik van Riel <riel@redhat.com>, Mel Gorman <mgorman@suse.de>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: linux-next: Tree for Feb 4
Date: Thu, 5 Feb 2015 06:37:07 -0800 [thread overview]
Message-ID: <20150205143707.GX5370@linux.vnet.ibm.com> (raw)
In-Reply-To: <54D3186F.7030500@sr71.net>
On Wed, Feb 04, 2015 at 11:14:55PM -0800, Dave Hansen wrote:
> On 02/04/2015 05:53 PM, Sedat Dilek wrote:
> > The architecture-specific switch_mm() function can be called by offline
> > CPUs, but includes event tracing, which cannot be legally carried out
> > on offline CPUs. This results in a lockdep-RCU splat. This commit fixes
> > this splat by omitting the tracing when the CPU is offline.
> ...
> >>> >> > load_cr3(next->pgd);
> >>> >> > - trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
> >>> >> > + if (cpu_online(smp_processor_id()))
> >>> >> > + trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);
>
> Is this, perhaps, something that we should be doing in the generic trace
> code so that all of the trace users don't have to worry about it? Also,
> this patch will add overhead to the code when tracing is off. It would
> be best if we could manage to make the cpu_online() check only in the
> cases where the tracepoint is on.
I considered doing this in the _rcuidle piece of the trace code, but
unlike the RCU idle exit/entry in the _rcuidle stuff, the work required
to get through the RCU online/offline code is pretty heavyweight.
You end up having 16 CPUs contending for an rcu_node lock, for example.
But maybe you are instead suggesting pushing only the cpu_online() check
into the trace infrastructure. If so, fair point, and I will take a
look at this.
Thanx, Paul
next prev parent reply other threads:[~2015-02-05 14:37 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-04 8:35 linux-next: Tree for Feb 4 Stephen Rothwell
2015-02-04 12:26 ` Sedat Dilek
2015-02-04 15:16 ` Jens Axboe
2015-02-04 15:21 ` Sedat Dilek
2015-02-04 15:31 ` Jens Axboe
2015-02-04 15:36 ` Sedat Dilek
2015-02-04 15:58 ` Martin K. Petersen
2015-02-04 16:06 ` Sedat Dilek
2015-02-05 3:17 ` Martin K. Petersen
2015-02-05 3:41 ` Sedat Dilek
2015-02-05 19:46 ` Sedat Dilek
2015-02-06 15:24 ` Sedat Dilek
2015-02-04 20:18 ` Sedat Dilek
2015-02-04 21:54 ` Rafael J. Wysocki
2015-02-04 21:53 ` Paul E. McKenney
2015-02-04 22:59 ` Rafael J. Wysocki
2015-02-04 23:51 ` Paul E. McKenney
2015-02-04 23:58 ` Sedat Dilek
2015-02-05 0:10 ` Paul E. McKenney
2015-02-05 0:30 ` Sedat Dilek
2015-02-05 0:57 ` Paul E. McKenney
2015-02-05 1:18 ` Sedat Dilek
2015-02-05 1:51 ` Paul E. McKenney
2015-02-05 1:53 ` Sedat Dilek
2015-02-05 2:12 ` Sedat Dilek
2015-02-05 4:13 ` Paul E. McKenney
2015-02-05 7:14 ` Dave Hansen
2015-02-05 14:37 ` Paul E. McKenney [this message]
2015-02-05 14:57 ` Sedat Dilek
2015-02-05 16:58 ` Paul E. McKenney
2015-02-05 18:03 ` Steven Rostedt
2015-02-05 18:08 ` Steven Rostedt
2015-02-05 18:11 ` Dave Hansen
2015-02-05 18:34 ` Paul E. McKenney
2015-02-05 18:35 ` Dave Hansen
2015-02-05 18:45 ` Paul E. McKenney
2015-02-05 19:25 ` Sedat Dilek
2015-02-05 19:33 ` Paul E. McKenney
2015-02-05 19:42 ` Sedat Dilek
2015-02-05 19:58 ` Steven Rostedt
2015-02-05 20:07 ` Sedat Dilek
2015-02-05 20:22 ` Steven Rostedt
2015-02-05 20:50 ` Sedat Dilek
2015-02-05 21:45 ` Sedat Dilek
2015-02-05 22:09 ` Steven Rostedt
2015-02-05 22:16 ` Sedat Dilek
2015-02-05 23:11 ` Steven Rostedt
2015-02-05 23:53 ` Sedat Dilek
2015-02-06 0:03 ` Sedat Dilek
2015-02-06 0:12 ` Steven Rostedt
2015-02-06 0:14 ` Sedat Dilek
2015-02-04 22:38 ` Sedat Dilek
2015-02-04 23:25 ` Rafael J. Wysocki
2015-02-04 23:54 ` Sedat Dilek
2015-02-04 22:46 ` Sedat Dilek
2015-02-04 23:30 ` Rafael J. Wysocki
2015-02-04 23:48 ` Sedat Dilek
-- strict thread matches above, loose matches on Subject: below --
2022-02-04 4:14 Stephen Rothwell
2021-02-04 9:13 Stephen Rothwell
2020-02-04 4:19 Stephen Rothwell
2019-02-04 5:35 Stephen Rothwell
2016-02-04 3:48 Stephen Rothwell
2014-02-04 5:07 Stephen Rothwell
[not found] ` <CAP=VYLpgLC_4yuPtQH_yAd8S9cqQAVu2uB2=Wf3q_zgY4uzkLw@mail.gmail.com>
2014-02-04 22:23 ` Stephen Rothwell
2014-02-05 0:41 ` Stephen Rothwell
2013-02-04 7:39 Stephen Rothwell
2013-02-04 13:56 ` James Hogan
2013-02-04 20:33 ` Stephen Rothwell
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