From: Johan Hovold <johan@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Johan Hovold <johan+linaro@kernel.org>,
Marc Zyngier <maz@kernel.org>,
x86@kernel.org, platform-driver-x86@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org,
linux-kernel@vger.kernel.org, Hsin-Yi Wang <hsinyi@chromium.org>,
Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Subject: Re: [PATCH v4 19/19] irqdomain: Switch to per-domain locking
Date: Wed, 18 Jan 2023 10:51:43 +0100 [thread overview]
Message-ID: <Y8fBL+h2l5Wsiq2Z@hovoldconsulting.com> (raw)
In-Reply-To: <87mt6gkez4.ffs@tglx>
On Tue, Jan 17, 2023 at 10:50:39PM +0100, Thomas Gleixner wrote:
> On Mon, Jan 16 2023 at 14:50, Johan Hovold wrote:
> > The IRQ domain structures are currently protected by the global
> > irq_domain_mutex. Switch to using more fine-grained per-domain locking,
> > which may potentially speed up parallel probing somewhat.
>
> Does it or not?
>
> If not then why adding all this churn for no real value?
It probably doesn't make much difference, but Marc wanted per-domain
locking:
> I'd really like to avoid a global mutex. At the very least this should
> be a per-domain mutex, otherwise this will serialise a lot more than
> what is needed.
Yeah, I considered that too, but wanted to get your comments on this
first.
Also note that the likewise global irq_domain_mutex (and
sparse_irq_lock) are taken in some of these paths so perhaps using finer
locking won't actually matter that much as this is mostly for parallel
probing.
https://lore.kernel.org/lkml/YuKHiZuNvN+K9NCc@hovoldconsulting.com/
As part of fixing the races, this series has now replaced the per-domain
revmap mutexes with the global irq_domain_mutex, which could possibly be
perceived as a step in the wrong direction in this respect.
This patch restores per-domain locking for non-hierarchical domains and
extends it to hierarchical domains. This leaves the irq_domain_mutex to
only be used for things that actually need a global lock such as the
domain list.
I consider this mostly a clean up, and I did intentionally place it last
in order to not have the fixes depend on it.
Johan
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next prev parent reply other threads:[~2023-01-18 9:52 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-16 13:50 [PATCH v4 00/19] irqdomain: fix mapping race and clean up locking Johan Hovold
2023-01-16 13:50 ` [PATCH v4 01/19] irqdomain: Drop bogus fwspec-mapping error handling Johan Hovold
2023-01-17 21:17 ` Thomas Gleixner
2023-01-16 13:50 ` [PATCH v4 02/19] irqdomain: Drop dead domain-name assignment Johan Hovold
2023-01-17 21:18 ` Thomas Gleixner
2023-01-16 13:50 ` [PATCH v4 03/19] irqdomain: Drop leftover brackets Johan Hovold
2023-01-17 21:19 ` Thomas Gleixner
2023-01-18 9:05 ` Johan Hovold
2023-01-16 13:50 ` [PATCH v4 04/19] irqdomain: Fix association race Johan Hovold
2023-01-17 21:20 ` Thomas Gleixner
2023-01-16 13:50 ` [PATCH v4 05/19] irqdomain: Fix disassociation race Johan Hovold
2023-01-16 13:50 ` [PATCH v4 06/19] irqdomain: Drop revmap mutex Johan Hovold
2023-01-17 21:23 ` Thomas Gleixner
2023-01-18 9:22 ` Johan Hovold
2023-01-18 13:05 ` Thomas Gleixner
2023-01-18 13:10 ` Johan Hovold
2023-02-06 13:09 ` Thomas Gleixner
2023-02-06 17:10 ` Johan Hovold
2023-01-16 13:50 ` [PATCH v4 07/19] irqdomain: Look for existing mapping only once Johan Hovold
2023-01-17 21:34 ` Thomas Gleixner
2023-01-18 9:26 ` Johan Hovold
2023-02-09 13:00 ` Johan Hovold
2023-01-16 13:50 ` [PATCH v4 08/19] irqdomain: Refactor __irq_domain_alloc_irqs() Johan Hovold
2023-01-17 21:34 ` Thomas Gleixner
2023-01-18 9:30 ` Johan Hovold
2023-01-16 13:50 ` [PATCH v4 09/19] irqdomain: Fix mapping-creation race Johan Hovold
2023-01-17 21:39 ` Thomas Gleixner
2023-01-18 9:40 ` Johan Hovold
2023-02-09 13:08 ` Johan Hovold
2023-01-16 13:50 ` [PATCH v4 10/19] irqdomain: Clean up irq_domain_push/pop_irq() Johan Hovold
2023-01-16 13:50 ` [PATCH v4 11/19] x86/ioapic: Use irq_domain_create_hierarchy() Johan Hovold
2023-01-17 21:41 ` Thomas Gleixner
2023-01-18 10:31 ` Johan Hovold
2023-01-16 13:50 ` [PATCH v4 12/19] x86/apic: " Johan Hovold
2023-01-16 13:50 ` [PATCH v4 13/19] irqchip/alpine-msi: Use irq_domain_add_hierarchy() Johan Hovold
2023-01-16 13:50 ` [PATCH v4 14/19] irqchip/gic-v2m: Use irq_domain_create_hierarchy() Johan Hovold
2023-01-16 13:50 ` [PATCH v4 15/19] irqchip/gic-v3-its: " Johan Hovold
2023-01-16 13:50 ` [PATCH v4 16/19] irqchip/gic-v3-mbi: " Johan Hovold
2023-01-16 13:50 ` [PATCH v4 17/19] irqchip/loongson-pch-msi: " Johan Hovold
2023-01-16 13:50 ` [PATCH v4 18/19] irqchip/mvebu-odmi: " Johan Hovold
2023-01-16 13:50 ` [PATCH v4 19/19] irqdomain: Switch to per-domain locking Johan Hovold
2023-01-17 21:50 ` Thomas Gleixner
2023-01-18 9:51 ` Johan Hovold [this message]
2023-01-18 13:09 ` Thomas Gleixner
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