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From: "Pavel Machek" <pavel@ucw.cz>
To: cip-dev@lists.cip-project.org
Cc: Pavel Machek <pavel@denx.de>,
	Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>,
	Biju Das <biju.das.jz@bp.renesas.com>
Subject: Re: [cip-dev] [RFC PATCH 4.19.y-cip 24/50] PCI: endpoint: Replace spinlock with mutex
Date: Wed, 21 Oct 2020 20:34:16 +0200	[thread overview]
Message-ID: <20201021183416.GA10468@duo.ucw.cz> (raw)
In-Reply-To: <OSBPR01MB5048F76FC81C94ED7FE1C553AA1F0@OSBPR01MB5048.jpnprd01.prod.outlook.com>


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Hi!

> > > commit 3d3248dbd018502f654064c78efcd2e165ab3486 upstream.
> > >
> > > The pci_epc_ops is not intended to be invoked from interrupt context.
> > > Hence replace spin_lock_irqsave and spin_unlock_irqrestore with
> > > mutex_lock and mutex_unlock respectively.
> > 
> > Could I get some kind of explanation why this is good idea?
> > 
> Apart of one mentioned above other point I would add is on a single core machine mutex_lock/unlock would be good choice.
> 
> Also to add the callbacks in controller driver might sleep. For example in raise_irq callback  [1], [2].
> 
> > As long as code protected by the locks does not sleep, spinlocks are
> > okay... (but they should not need "_irqsave" variants).
> > 
> > They are likely to have better performance, too, when protected code
> > is small and fast.
> > 
> I do agree with the above two points *if the code isn't sleeping*.

Okay, we can't really protect sleeping code with a mutex.

> [1] https://git.kernel.org/pub/scm/linux/kernel/git/cip/linux-cip.git/tree/drivers/pci/controller/pcie-rockchip-ep.c?h=linux-4.19.y-cip#n410

But this one is not sleeping. It is mdelay(), not msleep().

> [2] https://git.kernel.org/pub/scm/linux/kernel/git/cip/linux-cip.git/tree/drivers/pci/controller/pcie-cadence-ep.c?h=linux-4.19.y-cip#n310

And same here.

If there's a place which does sleep with the spinlock held, I'd still
be curious.

OTOH, 1 msec is already threshold where mutex makes sense, so... this
is okay.

Thanks,
								Pavel
-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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  reply	other threads:[~2020-10-21 18:34 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-12 14:18 [cip-dev] [RFC PATCH 4.19.y-cip 00/50] Add PCIe EP support for Renesas R-Car Gen3 and RZ/G2x Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 01/50] PCI: endpoint: Add new pci_epc_ops to get EPC features Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 02/50] PCI: dwc: Add ->get_features() callback function to dw_pcie_ep_ops Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 03/50] PCI: designware-plat: Populate ->get_features() dw_pcie_ep_ops Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 04/50] PCI: pci-dra7xx: " Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 05/50] PCI: rockchip: " Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 06/50] PCI: cadence: Populate ->get_features() cdns_pcie_epc_ops Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 07/50] PCI: endpoint: Add helper to get first unreserved BAR Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 08/50] PCI: endpoint: Fix pci_epf_alloc_space() to set correct MEM TYPE flags Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 09/50] PCI: pci-epf-test: Remove setting epf_bar flags in function driver Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 10/50] PCI: pci-epf-test: Do not allocate next BARs memory if current BAR is 64Bit Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 11/50] PCI: pci-epf-test: Use pci_epc_get_features() to get EPC features Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 12/50] PCI: cadence: Remove pci_epf_linkup() from Cadence EP driver Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 13/50] PCI: rockchip: Remove pci_epf_linkup() from Rockchip " Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 14/50] PCI: designware-plat: Remove setting epc->features in Designware plat " Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 15/50] PCI: endpoint: Remove features member in struct pci_epc Lad Prabhakar
2020-10-12 14:18 ` [cip-dev] [RFC PATCH 4.19.y-cip 16/50] PCI: endpoint: Fix a potential NULL pointer dereference Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 17/50] PCI: endpoint: Add support to specify alignment for buffers allocated to BARs Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 18/50] PCI: endpoint: Set endpoint controller pointer to NULL Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 19/50] PCI: endpoint: Allocate enough space for fixed size BAR Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 20/50] PCI: endpoint: Skip odd BAR when skipping 64bit BAR Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 21/50] PCI: endpoint: Clear BAR before freeing its space Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 22/50] PCI: endpoint: Cast the page number to phys_addr_t Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 23/50] PCI: endpoint: Use notification chain mechanism to notify EPC events to EPF Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 24/50] PCI: endpoint: Replace spinlock with mutex Lad Prabhakar
2020-10-20 20:43   ` Pavel Machek
2020-10-20 21:56     ` Lad Prabhakar
2020-10-21 18:34       ` Pavel Machek [this message]
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 25/50] PCI: endpoint: Protect concurrent access to pci_epf_ops " Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 26/50] PCI: endpoint: Assign function number for each PF in EPC core Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 27/50] PCI: endpoint: Add core init notifying feature Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 28/50] PCI: endpoint: Add notification for core init completion Lad Prabhakar
2020-10-21 19:00   ` Pavel Machek
2020-10-21 20:16     ` Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 29/50] PCI: pci-epf-test: Add support to defer core initialization Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 30/50] PCI: endpoint: Fix clearing start entry in configfs Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 31/50] PCI: endpoint: Fix ->set_msix() to take BIR and offset as arguments Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 32/50] PCI: dwc: Fix dw_pcie_ep_raise_msix_irq() to get correct MSI-X table address Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 33/50] PCI: endpoint: Pass page size as argument to pci_epc_mem_init() Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 34/50] PCI: endpoint: Add support to handle multiple base for mapping outbound memory Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 35/50] PCI: endpoint: functions/pci-epf-test: Print throughput information Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 36/50] PCI: rcar: Rename pcie-rcar.c to pcie-rcar-host.c Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 37/50] arm64: defconfig: Enable CONFIG_PCIE_RCAR_HOST Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 38/50] PCI: rcar: Move shareable code to a common file Lad Prabhakar
2020-10-21 19:06   ` Pavel Machek
2020-10-21 20:28     ` Lad Prabhakar
2020-10-22 19:42       ` Pavel Machek
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 39/50] PCI: rcar: Fix calculating mask for PCIEPAMR register Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 40/50] dt-bindings: PCI: rcar: Add bindings for R-Car PCIe endpoint controller Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 41/50] PCI: rcar: Add endpoint mode support Lad Prabhakar
2020-10-14  9:22   ` Pavel Machek
2020-10-15 16:31     ` Lad Prabhakar
2020-10-15 18:01       ` Pavel Machek
2020-10-22 18:23         ` Pavel Machek
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 42/50] arm64: defconfig: Enable R-Car PCIe endpoint driver Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 43/50] dt-bindings: pci: rcar-pci-ep: Document r8a774a1 and r8a774b1 Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 44/50] arm64: dts: renesas: r8a774c0: Add PCIe EP node Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 45/50] arm64: dts: renesas: r8a774a1: Add PCIe EP nodes Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 46/50] arm64: dts: renesas: r8a774b1: " Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 47/50] misc: pci_endpoint_test: Add Device ID for RZ/G2E PCIe controller Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 48/50] misc: pci_endpoint_test: Add Device ID for RZ/G2M and RZ/G2N PCIe controllers Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 49/50] tools: PCI: Exit with error code when test fails Lad Prabhakar
2020-10-12 14:19 ` [cip-dev] [RFC PATCH 4.19.y-cip 50/50] tools: PCI: Fix fd leakage Lad Prabhakar
2020-10-14  9:39 ` [cip-dev] If you are using PCIe EP, speak up was Re: [RFC PATCH 4.19.y-cip 00/50] Add PCIe EP support for Renesas R-Car Gen3 and RZ/G2x Pavel Machek
2020-10-15 16:18   ` Lad Prabhakar
2020-10-20  7:16   ` Lad Prabhakar
2020-10-20 10:34     ` Pavel Machek
2020-10-20 12:01     ` Pavel Machek
2020-10-20 13:01       ` Lad Prabhakar
2020-10-20 20:48         ` Pavel Machek
2020-10-20 21:58           ` Lad Prabhakar
2020-10-14 10:07 ` [cip-dev] " Pavel Machek
2020-10-15 16:27   ` Lad Prabhakar

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