From: Chris Metcalf <cmetcalf@ezchip.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Gilad Ben Yossef <giladb@ezchip.com>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Rik van Riel <riel@redhat.com>, Tejun Heo <tj@kernel.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Christoph Lameter <cl@linux.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Andy Lutomirski <luto@amacapital.net>,
<linux-doc@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v9 06/13] task_isolation: add debug boot flag
Date: Mon, 4 Jan 2016 18:42:00 -0500 [thread overview]
Message-ID: <568B0348.2040601@ezchip.com> (raw)
In-Reply-To: <20160104175220.310be95c@gandalf.local.home>
On 1/4/2016 5:52 PM, Steven Rostedt wrote:
> On Mon, 4 Jan 2016 14:34:44 -0500
> Chris Metcalf<cmetcalf@ezchip.com> wrote:
>
>
>> >+#ifdef CONFIG_TASK_ISOLATION
>> >+void task_isolation_debug(int cpu)
>> >+{
>> >+ struct task_struct *p;
>> >+
>> >+ if (!task_isolation_possible(cpu))
>> >+ return;
>> >+
>> >+ rcu_read_lock();
> What's the rcu_read_lock() for? I don't see what is being protected by
> rcu here?
I'm not completely clear either, but this is the same idiom as is used throughout
kernel/sched/core.c when mapping from a pid or a cpu to a task_struct, since
obviously you could end up racing with the task_struct being removed after the
task dies. My best understanding is that the rcu_read_lock() holds up the final
free of the structure so that we have time here to get another reference to it.
See for example sched_setaffinity() for a similar use of the idiom.
--
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com
next prev parent reply other threads:[~2016-01-04 23:42 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-04 19:34 [PATCH v9 00/13] support "task_isolation" mode for nohz_full Chris Metcalf
2016-01-04 19:34 ` [PATCH v9 01/13] vmstat: provide a function to quiet down the diff processing Chris Metcalf
2016-01-04 19:34 ` [PATCH v9 02/13] vmstat: add vmstat_idle function Chris Metcalf
2016-01-04 19:34 ` [PATCH v9 03/13] lru_add_drain_all: factor out lru_add_drain_needed Chris Metcalf
2016-01-04 19:34 ` [PATCH v9 04/13] task_isolation: add initial support Chris Metcalf
2016-01-19 15:42 ` Frederic Weisbecker
2016-01-19 20:45 ` Chris Metcalf
2016-01-28 0:28 ` Frederic Weisbecker
2016-01-29 18:18 ` Chris Metcalf
2016-01-30 21:11 ` Frederic Weisbecker
2016-02-11 19:24 ` Chris Metcalf
2016-03-04 12:56 ` Frederic Weisbecker
2016-03-09 19:39 ` Chris Metcalf
2016-04-08 13:56 ` Frederic Weisbecker
2016-04-08 16:34 ` Chris Metcalf
2016-04-12 18:41 ` Chris Metcalf
2016-04-22 13:16 ` Frederic Weisbecker
2016-04-25 20:36 ` Chris Metcalf
2016-05-26 1:07 ` Frederic Weisbecker
2016-06-03 19:32 ` Chris Metcalf
2016-06-29 15:18 ` Frederic Weisbecker
2016-07-01 20:59 ` Chris Metcalf
2016-07-05 14:41 ` Frederic Weisbecker
2016-07-05 17:47 ` Christoph Lameter
2016-01-04 19:34 ` [PATCH v9 05/13] task_isolation: support PR_TASK_ISOLATION_STRICT mode Chris Metcalf
2016-01-04 19:34 ` [PATCH v9 06/13] task_isolation: add debug boot flag Chris Metcalf
2016-01-04 22:52 ` Steven Rostedt
2016-01-04 23:42 ` Chris Metcalf [this message]
2016-01-05 13:42 ` Steven Rostedt
2016-01-04 19:34 ` [PATCH v9 07/13] arch/x86: enable task isolation functionality Chris Metcalf
2016-01-04 21:02 ` [PATCH v9bis " Chris Metcalf
2016-01-04 19:34 ` [PATCH v9 08/13] arch/arm64: adopt prepare_exit_to_usermode() model from x86 Chris Metcalf
2016-01-04 20:33 ` Mark Rutland
2016-01-04 21:01 ` Chris Metcalf
2016-01-05 17:21 ` Mark Rutland
2016-01-05 17:33 ` [PATCH 1/2] arm64: entry: remove pointless SPSR mode check Mark Rutland
2016-01-06 12:15 ` Catalin Marinas
2016-01-05 17:33 ` [PATCH 2/2] arm64: factor work_pending state machine to C Mark Rutland
2016-01-05 18:53 ` Chris Metcalf
2016-01-06 12:30 ` Catalin Marinas
2016-01-06 12:47 ` Mark Rutland
2016-01-06 13:43 ` Mark Rutland
2016-01-06 14:17 ` Catalin Marinas
2016-01-04 22:31 ` [PATCH v9 08/13] arch/arm64: adopt prepare_exit_to_usermode() model from x86 Andy Lutomirski
2016-01-05 18:01 ` Mark Rutland
2016-01-04 19:34 ` [PATCH v9 09/13] arch/arm64: enable task isolation functionality Chris Metcalf
2016-01-04 19:34 ` [PATCH v9 10/13] arch/tile: adopt prepare_exit_to_usermode() model from x86 Chris Metcalf
2016-01-04 19:34 ` [PATCH v9 11/13] arch/tile: move user_exit() to early kernel entry sequence Chris Metcalf
2016-01-04 19:34 ` [PATCH v9 12/13] arch/tile: enable task isolation functionality Chris Metcalf
2016-01-04 19:34 ` [PATCH v9 13/13] arm, tile: turn off timer tick for oneshot_stopped state Chris Metcalf
2016-01-11 21:15 ` [PATCH v9 00/13] support "task_isolation" mode for nohz_full Chris Metcalf
2016-01-12 10:07 ` Will Deacon
2016-01-12 17:49 ` Chris Metcalf
2016-01-13 10:44 ` Ingo Molnar
2016-01-13 21:19 ` Chris Metcalf
2016-01-20 13:27 ` Mark Rutland
2016-01-12 10:53 ` Ingo Molnar
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