linux-kernel - [patch 0/8] genirq, perf: Cleanup the abuse of irq_set_affinity

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Date:   Tue, 18 May 2021 11:17:25 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Robin Murphy <robin.murphy@....com>,
        Nitesh Lal <nilal@...hat.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org, Frank Li <Frank.li@....com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Shaokun Zhang <zhangshaokun@...ilicon.com>
Subject: [patch 0/8] genirq, perf: Cleanup the abuse of irq_set_affinity_hint()

The modular PMU drivers use irq_set_affinity_hint() to set the affinity
for the PMU interrupts, which relies on the undocumented side effect that
this function actually sets the affinity under the hood.

Setting an hint is clearly not a guarantee and for these PMU interrupts an
affinity hint, which is supposed to guide userspace for setting affinity,
is beyond pointless, because the affinity of these interrupts cannot be
modified from user space.

Aside of that the error checks are bogus because the only error which is
returned from irq_set_affinity_hint() is when there is no irq descriptor
for the interrupt number, but not when the affinity set fails. That's on
purpose because the hint can point to an offline CPU.

Sigh, if people would at least talk if something is missing...

Clean up the mess by exposing irq_set_affinity() and converting the drivers
over to that.

Thanks,

	tglx
---
 drivers/perf/arm-ccn.c                        |    6 +---
 drivers/perf/arm-cmn.c                        |    9 +-----
 drivers/perf/arm_dmc620_pmu.c                 |    5 +--
 drivers/perf/arm_dsu_pmu.c                    |    8 +----
 drivers/perf/arm_smmuv3_pmu.c                 |   10 ++-----
 drivers/perf/fsl_imx8_ddr_perf.c              |    5 +--
 drivers/perf/hisilicon/hisi_uncore_ddrc_pmu.c |    3 --
 drivers/perf/hisilicon/hisi_uncore_hha_pmu.c  |    3 --
 drivers/perf/hisilicon/hisi_uncore_l3c_pmu.c  |    3 --
 drivers/perf/hisilicon/hisi_uncore_pa_pmu.c   |    3 --
 drivers/perf/hisilicon/hisi_uncore_pmu.c      |    4 +-
 drivers/perf/hisilicon/hisi_uncore_sllc_pmu.c |    3 --
 include/linux/interrupt.h                     |   35 +-------------------------
 kernel/irq/manage.c                           |   33 +++++++++++++++++++++++-
 14 files changed, 49 insertions(+), 81 deletions(-)