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From: Peter Zijlstra <peterz@infradead.org>
To: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc: Nishanth Aravamudan <naravamudan@digitalocean.com>,
	Julien Desfossez <jdesfossez@digitalocean.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Vineeth Pillai <viremana@linux.microsoft.com>,
	Aaron Lu <aaron.lwe@gmail.com>,
	Aubrey Li <aubrey.intel@gmail.com>,
	tglx@linutronix.de, linux-kernel@vger.kernel.org,
	mingo@kernel.org, torvalds@linux-foundation.org,
	fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com,
	Phil Auld <pauld@redhat.com>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	vineeth@bitbyteword.org, Chen Yu <yu.c.chen@intel.com>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Agata Gruza <agata.gruza@intel.com>,
	Antonio Gomez Iglesias <antonio.gomez.iglesias@intel.com>,
	graf@amazon.com, konrad.wilk@oracle.com, dfaggioli@suse.com,
	pjt@google.com, rostedt@goodmis.org, derkling@google.com,
	benbjiang@tencent.com,
	Alexandre Chartre <alexandre.chartre@oracle.com>,
	James.Bottomley@hansenpartnership.com, OWeisse@umich.edu,
	Dhaval Giani <dhaval.giani@oracle.com>,
	Junaid Shahid <junaids@google.com>,
	jsbarnes@google.com, chris.hyser@oracle.com,
	Ben Segall <bsegall@google.com>, Josh Don <joshdon@google.com>,
	Hao Luo <haoluo@google.com>,
	Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH v10 2/5] sched: CGroup tagging interface for core scheduling
Date: Thu, 4 Feb 2021 15:35:50 +0100	[thread overview]
Message-ID: <YBwGRpnISmwkJ2i8@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210123011704.1901835-3-joel@joelfernandes.org>

On Fri, Jan 22, 2021 at 08:17:01PM -0500, Joel Fernandes (Google) wrote:
> +static inline void __sched_core_erase_cookie(struct sched_core_cookie *cookie)
> +{
> +	lockdep_assert_held(&sched_core_cookies_lock);
> +
> +	/* Already removed */
> +	if (RB_EMPTY_NODE(&cookie->node))
> +		return;
> +
> +	rb_erase(&cookie->node, &sched_core_cookies);
> +	RB_CLEAR_NODE(&cookie->node);
> +}
> +
> +/* Called when a task no longer points to the cookie in question */
> +static void sched_core_put_cookie(struct sched_core_cookie *cookie)
> +{
> +	unsigned long flags;
> +
> +	if (!cookie)
> +		return;
> +
> +	if (refcount_dec_and_test(&cookie->refcnt)) {
> +		raw_spin_lock_irqsave(&sched_core_cookies_lock, flags);
> +		__sched_core_erase_cookie(cookie);
> +		raw_spin_unlock_irqrestore(&sched_core_cookies_lock, flags);
> +		kfree(cookie);
> +	}
> +}

> +static void __sched_core_update_cookie(struct task_struct *p)
> +{

> +	raw_spin_lock(&sched_core_cookies_lock);

> +		/*
> +		 * Cookie exists, increment refcnt. If refcnt is currently 0,
> +		 * we're racing with a put() (refcnt decremented but cookie not
> +		 * yet removed from the tree). In this case, we can simply
> +		 * perform the removal ourselves and retry.
> +		 * sched_core_put_cookie() will still function correctly.
> +		 */
> +		if (unlikely(!refcount_inc_not_zero(&match->refcnt))) {
> +			__sched_core_erase_cookie(match);
> +			goto retry;
> +		}

refcount_dec_and_lock() avoids that complication.

  parent reply	other threads:[~2021-02-04 14:40 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-23  1:16 [PATCH v10 0/5] Core scheduling remaining patches Joel Fernandes (Google)
2021-01-23  1:17 ` [PATCH v10 1/5] sched: migration changes for core scheduling Joel Fernandes (Google)
2021-01-23  1:17 ` [PATCH v10 2/5] sched: CGroup tagging interface " Joel Fernandes (Google)
2021-02-03 16:51   ` Peter Zijlstra
2021-02-04 13:59     ` Peter Zijlstra
2021-02-05 16:42       ` Joel Fernandes
2021-02-04 13:54   ` Peter Zijlstra
2021-02-05  3:45     ` Josh Don
2021-02-04 13:57   ` Peter Zijlstra
2021-02-04 20:52     ` Chris Hyser
2021-02-05 10:43       ` Peter Zijlstra
2021-02-05 22:19         ` Chris Hyser
2021-02-04 14:01   ` Peter Zijlstra
2021-02-05  3:55     ` Josh Don
2021-02-04 14:35   ` Peter Zijlstra [this message]
2021-02-05  4:07     ` Josh Don
2021-02-04 14:52   ` Peter Zijlstra
2021-02-05 16:37     ` Joel Fernandes
2021-02-05 11:41   ` Peter Zijlstra
2021-02-05 11:52   ` Peter Zijlstra
2021-02-06  1:15     ` Josh Don
2021-02-05 12:00   ` Peter Zijlstra
2021-02-23  4:00   ` Chris Hyser
2021-02-23  9:05     ` Peter Zijlstra
2021-02-23 19:25       ` Chris Hyser
2021-02-24  5:15         ` Josh Don
2021-02-24 13:02           ` Chris Hyser
2021-02-24 13:52             ` chris hyser
2021-02-24 15:47               ` chris hyser
2021-02-26 20:07                 ` Chris Hyser
2021-03-01 21:01                   ` Josh Don
2021-01-23  1:17 ` [PATCH v10 3/5] kselftest: Add tests for core-sched interface Joel Fernandes (Google)
2021-01-23  1:17 ` [PATCH v10 4/5] Documentation: Add core scheduling documentation Joel Fernandes (Google)
2021-01-23  1:17 ` [PATCH v10 5/5] sched: Debug bits Joel Fernandes (Google)

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