From: Thomas Gleixner <tglx@linutronix.de>
To: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Bjorn Helgaas <bhelgaas@google.com>,
Randy Dunlap <rdunlap@infradead.org>,
Yinghai Lu <yinghai@kernel.org>, Borislav Petkov <bp@alien8.de>,
Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
x86@kernel.org, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Andrew Morton <akpm@linux-foundation.org>,
Tony Luck <tony.luck@intel.com>, Joerg Roedel <joro@8bytes.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org
Subject: Re: [Patch v7 14/18] x86, irq, ACPI: Introduce a rwsem to protect IOAPIC operations from hotplug
Date: Sat, 1 Nov 2014 19:59:39 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.11.1411011949370.5308@nanos> (raw)
In-Reply-To: <1414387308-27148-15-git-send-email-jiang.liu@linux.intel.com>
On Mon, 27 Oct 2014, Jiang Liu wrote:
> We are going to support ACPI based IOAPIC hotplug, so introduce a rwsem
> to protect IOAPIC data structures from IOAPIC hotplug. We choose to
> serialize in ACPI instead of in the IOAPIC core because:
> 1) currently we are only plan to support ACPI based IOAPIC hotplug
> 2) it's much more cleaner and easier
> 3) It does't affect IOAPIC discovered by devicetree, SFI and mpparse.
I had a last intensive look at this series as I was about to merge
it. So I looked at the locking rules here again
> +/*
> + * Locks related to IOAPIC hotplug
> + * Hotplug side:
> + * ->lock_device_hotplug() //device_hotplug_lock
> + * ->acpi_ioapic_rwsem
> + * ->ioapic_lock
> + * Interrupt mapping side:
> + * ->acpi_ioapic_rwsem
> + * ->ioapic_mutex
> + * ->ioapic_lock
> + */
This looks sane, but I cannot figure out at all why this needs to be a
rwsem.
> +static DECLARE_RWSEM(acpi_ioapic_rwsem);
I think it should be a simple mutex because the rwsem does not protect
against concurrent execution what taken for read.
And the site which takes it for write is in the early boot process
where nothing runs in parallel AFAICT.
Thanks,
tglx
next prev parent reply other threads:[~2014-11-01 18:59 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-27 5:21 [Patch v7 00/18] Enable support of IOAPIC hotplug on x86 platforms Jiang Liu
2014-10-27 5:21 ` [Patch v7 01/18] ACPI, irq: fix regression casued by 6b9fb7082409 Jiang Liu
2014-10-28 17:44 ` Pavel Machek
2014-10-28 18:13 ` Bjorn Helgaas
2014-10-28 18:45 ` Thomas Gleixner
2014-10-27 5:21 ` [Patch v7 02/18] x86, intel-mid: Create IRQs for APB timers and RTC timers Jiang Liu
2014-10-27 5:21 ` [Patch v7 03/18] ACPI, irq, x86: Return IRQ instead of GSI in mp_register_gsi() Jiang Liu
2014-10-27 5:21 ` [Patch v7 04/18] x86, PCI, ACPI: Kill private function resource_to_addr() in arch/x86/pci/acpi.c Jiang Liu
2014-10-27 5:21 ` [Patch v7 05/18] ACPI: Correct return value of acpi_dev_resource_address_space() Jiang Liu
2014-10-27 22:30 ` Rafael J. Wysocki
2014-10-27 22:49 ` Bjorn Helgaas
2014-10-27 23:11 ` Rafael J. Wysocki
2014-10-28 1:13 ` Bjorn Helgaas
2014-10-27 5:21 ` [Patch v7 06/18] ACPI: Fix minor syntax issues in processor_core.c Jiang Liu
2014-10-27 5:21 ` [Patch v7 07/18] ACPI: Add interfaces to parse IOAPIC ID for IOAPIC hotplug Jiang Liu
2014-10-27 5:21 ` [Patch v7 08/18] PCI: Remove PCI ioapic driver Jiang Liu
2014-10-27 5:21 ` [Patch v7 09/18] x86, irq: Split out alloc_ioapic_save_registers() Jiang Liu
2014-10-27 5:21 ` [Patch v7 10/18] x86, irq: Prefer assigned ID in APIC ID register for x86_64 Jiang Liu
2014-10-27 5:21 ` [Patch v7 11/18] x86, irq: Remove __init marker for functions will be used by IOAPIC hotplug Jiang Liu
2014-10-27 5:21 ` [Patch v7 12/18] x86, irq: Keep balance of IOAPIC pin reference count Jiang Liu
2014-10-27 5:21 ` [Patch v7 13/18] x86, irq: Refine mp_register_ioapic() to prepare for IOAPIC hotplug Jiang Liu
2014-10-27 5:21 ` [Patch v7 14/18] x86, irq, ACPI: Introduce a rwsem to protect IOAPIC operations from hotplug Jiang Liu
2014-11-01 18:59 ` Thomas Gleixner [this message]
2014-11-02 5:24 ` Jiang Liu
2014-10-27 5:21 ` [Patch v7 15/18] x86, irq, ACPI: Implement interface to support ACPI based IOAPIC hot-addition Jiang Liu
2014-10-27 5:21 ` [Patch v7 16/18] x86, irq, ACPI: Implement interfaces to support ACPI based IOAPIC hot-removal Jiang Liu
2014-10-27 5:21 ` [Patch v7 17/18] x86, irq: Introduce helper to check whether an IOAPIC has been registered Jiang Liu
2014-10-28 17:47 ` Pavel Machek
2014-10-27 5:21 ` [Patch v7 18/18] x86, irq, ACPI: Implement ACPI driver to support IOAPIC hotplug Jiang Liu
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