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From: Robin Murphy <robin.murphy@arm.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	Nitesh Lal <nilal@redhat.com>,
	Jesse Brandeburg <jesse.brandeburg@intel.com>,
	"frederic@kernel.org" <frederic@kernel.org>,
	"juri.lelli@redhat.com" <juri.lelli@redhat.com>,
	Marcelo Tosatti <mtosatti@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>,
	linux-kernel@vger.kernel.org, intel-wired-lan@lists.osuosl.org,
	jbrandeb@kernel.org, Alex Belits <abelits@marvell.com>,
	"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
	"bhelgaas@google.com" <bhelgaas@google.com>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	"rostedt@goodmis.org" <rostedt@goodmis.org>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"davem@davemloft.net" <davem@davemloft.net>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"sfr@canb.auug.org.au" <sfr@canb.auug.org.au>,
	"stephen@networkplumber.org" <stephen@networkplumber.org>,
	"rppt@linux.vnet.ibm.com" <rppt@linux.vnet.ibm.com>,
	"jinyuqi@huawei.com" <jinyuqi@huawei.com>,
	"zhangshaokun@hisilicon.com" <zhangshaokun@hisilicon.com>,
	netdev@vger.kernel.org, chris.friesen@windriver.com,
	Marc Zyngier <maz@kernel.org>
Subject: Re: [PATCH tip:irq/core v1] genirq: remove auto-set of the mask when setting the hint
Date: Mon, 17 May 2021 19:50:35 +0100	[thread overview]
Message-ID: <d1d5e797-49ee-4968-88c6-c07119343492@arm.com> (raw)
In-Reply-To: <87sg2lz0zz.ffs@nanos.tec.linutronix.de>

On 2021-05-17 19:08, Thomas Gleixner wrote:
> On Mon, May 17 2021 at 18:26, Robin Murphy wrote:
>> On 2021-05-17 17:57, Nitesh Lal wrote:
>> I'm not implying that there isn't a bug, or that this code ever made
>> sense in the first place, just that fixing it will unfortunately be a
>> bit more involved than a simple revert. This patch as-is *will* subtly
>> break at least the system PMU drivers currently using
> 
> s/using/abusing/
> 
>> irq_set_affinity_hint() - those I know require the IRQ affinity to
>> follow whichever CPU the PMU context is bound to, in order to meet perf
>> core's assumptions about mutual exclusion.
> 
> Which driver is that?

Right now, any driver which wants to control an IRQ's affinity and also 
build as a module, for one thing. I'm familiar with drivers/perf/ where 
a basic pattern has been widely copied; some of the callers in other 
subsystems appear to *expect* it to set the underlying affinity as well, 
but whether any of those added within the last 6 years represent a 
functional dependency rather than just a performance concern I don't know.

Robin.

  reply	other threads:[~2021-05-17 18:50 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-01  2:18 Jesse Brandeburg
2021-05-04 12:15 ` Robin Murphy
2021-05-04 14:29   ` Nitesh Lal
2021-05-04 16:23   ` Jesse Brandeburg
2021-05-17 16:57     ` Nitesh Lal
2021-05-17 17:26       ` Robin Murphy
2021-05-17 18:08         ` Thomas Gleixner
2021-05-17 18:50           ` Robin Murphy [this message]
2021-05-17 19:08             ` Thomas Gleixner
2021-05-17 19:43               ` Thomas Gleixner
2021-05-17 20:18               ` Thomas Gleixner
2021-05-17 18:21         ` Nitesh Lal
2021-05-17 19:47           ` Thomas Gleixner
2021-05-17 21:13             ` Nitesh Lal
2021-05-17 20:48     ` Thomas Gleixner
2021-05-17 22:44       ` Nitesh Lal
2021-05-18  0:03         ` Thomas Gleixner
2021-05-18  0:23           ` Nitesh Lal
2021-05-20 21:57             ` Nitesh Lal
2021-05-21  0:03               ` Nitesh Lal
2021-05-21 11:56                 ` Thomas Gleixner
2021-05-21 12:03                   ` [PATCH] genirq: Provide new interfaces for affinity hints Thomas Gleixner
2021-05-21 15:45                     ` Lijun Pan
2021-05-21 21:45                       ` Thomas Gleixner
2021-05-21 16:13                     ` Nitesh Lal
2021-05-21 21:48                       ` Thomas Gleixner
2021-06-04 20:35                         ` Nitesh Lal
2021-05-27 10:03                     ` Shung-Hsi Yu
2021-05-27 10:21                       ` Shung-Hsi Yu
2021-05-27 13:06                       ` Nitesh Lal
2021-05-28  7:20                         ` Shung-Hsi Yu
2021-06-07 17:00                     ` Nitesh Lal
2021-06-14 16:12                       ` Nitesh Lal
2021-05-21 13:46                   ` [PATCH tip:irq/core v1] genirq: remove auto-set of the mask when setting the hint Nitesh Lal
2021-05-21 15:15                     ` Thomas Gleixner

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