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From: Marc Zyngier <maz@kernel.org>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: oliver.upton@linux.dev, james.morse@arm.com,
	suzuki.poulose@arm.com, yuzenghui@huawei.com,
	catalin.marinas@arm.com, will@kernel.org,
	linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev
Subject: Re: [PATCH 0/4] KVM: arm64: vgic: Locking fixes
Date: Fri, 19 May 2023 09:46:45 +0100	[thread overview]
Message-ID: <86cz2wlnd6.wl-maz@kernel.org> (raw)
In-Reply-To: <20230518100914.2837292-1-jean-philippe@linaro.org>

On Thu, 18 May 2023 11:09:14 +0100,
Jean-Philippe Brucker <jean-philippe@linaro.org> wrote:
> 
> Another fun locking puzzle, between the new config_lock and srcu.
> Patch 1 attempts to fix it, and the other patches fix simpler issues.

Thanks for that and for your excellent description of the problems.

> I got these lockdep reports while running KVM QEMU on a TCG QEMU, but it
> can also be triggered by running the vgic_irq kselftest on TCG QEMU.
> Now, with the fix and lockdep enabled, vgic_irq hangs but I believe it's
> an unrelated weirdness: if I introduce a separate lockdep warning for
> some made up locks, then the test passes again. So I'm sending this out
> now for discussion, and will investigate that one later.

I've taken these patches for a spin, and I cannot reproduce this hang,
though I'm running on actual HW and not QEMU. It would be really
annoying if lockdep actively introduced issues... :-/

Any chance you could dig into this as you have a good reproducer? I'll
try to setup a TGC environment on my end as well.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

WARNING: multiple messages have this Message-ID (diff)
From: Marc Zyngier <maz@kernel.org>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: oliver.upton@linux.dev, james.morse@arm.com,
	suzuki.poulose@arm.com, yuzenghui@huawei.com,
	catalin.marinas@arm.com, will@kernel.org,
	linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev
Subject: Re: [PATCH 0/4] KVM: arm64: vgic: Locking fixes
Date: Fri, 19 May 2023 09:46:45 +0100	[thread overview]
Message-ID: <86cz2wlnd6.wl-maz@kernel.org> (raw)
In-Reply-To: <20230518100914.2837292-1-jean-philippe@linaro.org>

On Thu, 18 May 2023 11:09:14 +0100,
Jean-Philippe Brucker <jean-philippe@linaro.org> wrote:
> 
> Another fun locking puzzle, between the new config_lock and srcu.
> Patch 1 attempts to fix it, and the other patches fix simpler issues.

Thanks for that and for your excellent description of the problems.

> I got these lockdep reports while running KVM QEMU on a TCG QEMU, but it
> can also be triggered by running the vgic_irq kselftest on TCG QEMU.
> Now, with the fix and lockdep enabled, vgic_irq hangs but I believe it's
> an unrelated weirdness: if I introduce a separate lockdep warning for
> some made up locks, then the test passes again. So I'm sending this out
> now for discussion, and will investigate that one later.

I've taken these patches for a spin, and I cannot reproduce this hang,
though I'm running on actual HW and not QEMU. It would be really
annoying if lockdep actively introduced issues... :-/

Any chance you could dig into this as you have a good reproducer? I'll
try to setup a TGC environment on my end as well.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2023-05-19  8:46 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-05-18 10:09 [PATCH 0/4] KVM: arm64: vgic: Locking fixes Jean-Philippe Brucker
2023-05-18 10:09 ` Jean-Philippe Brucker
2023-05-18 10:09 ` [PATCH 1/4] KVM: arm64: vgic: Fix a circular locking issue Jean-Philippe Brucker
2023-05-18 10:09   ` Jean-Philippe Brucker
2023-05-18 18:21   ` Oliver Upton
2023-05-18 18:21     ` Oliver Upton
2023-06-06 22:15   ` Nathan Chancellor
2023-06-07  5:23     ` Oliver Upton
2023-06-07  5:23       ` Oliver Upton
2023-06-07  8:37       ` Marc Zyngier
2023-06-07  8:37         ` Marc Zyngier
2023-06-07 13:28         ` Jean-Philippe Brucker
2023-06-07 13:28           ` Jean-Philippe Brucker
2023-06-07 15:04           ` Marc Zyngier
2023-06-07 15:04             ` Marc Zyngier
2023-06-07 15:29             ` Nathan Chancellor
2023-06-07 15:29               ` Nathan Chancellor
2023-06-07 15:42               ` Marc Zyngier
2023-06-07 15:42                 ` Marc Zyngier
2023-05-18 10:09 ` [PATCH 2/4] KVM: arm64: vgic: Wrap vgic_its_create() with config_lock Jean-Philippe Brucker
2023-05-18 10:09   ` Jean-Philippe Brucker
2023-05-18 10:09 ` [PATCH 3/4] KVM: arm64: vgic: Fix locking comment Jean-Philippe Brucker
2023-05-18 10:09   ` Jean-Philippe Brucker
2023-05-18 10:09 ` [PATCH 4/4] KVM: arm64: vgic: Fix a comment Jean-Philippe Brucker
2023-05-18 10:09   ` Jean-Philippe Brucker
2023-05-18 18:23 ` [PATCH 0/4] KVM: arm64: vgic: Locking fixes Oliver Upton
2023-05-18 18:23   ` Oliver Upton
2023-05-19  8:46 ` Marc Zyngier [this message]
2023-05-19  8:46   ` Marc Zyngier
2023-05-19 13:22   ` Jean-Philippe Brucker
2023-05-19 13:22     ` Jean-Philippe Brucker
2023-05-24 12:40   ` Jean-Philippe Brucker
2023-05-24 12:40     ` Jean-Philippe Brucker
2023-05-24 12:49 ` Marc Zyngier
2023-05-24 12:49   ` Marc Zyngier

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