From 714fe383d6c9bd95d0d2cad8cbeff3688342d025 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 16 Mar 2017 22:50:06 +0100 Subject: PCI: Provide Kconfig option for lockless config space accessors The generic PCI configuration space accessors are globally serialized via pci_lock. On larger systems this causes massive lock contention when the configuration space has to be accessed frequently. One such access pattern is the Intel Uncore performance counter unit. Provide a kernel config option which can be selected by an architecture when the low level PCI configuration space accessors in the architecture use their own serialization or can operate completely lockless. Signed-off-by: Thomas Gleixner Acked-by: Bjorn Helgaas Cc: Andi Kleen Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Borislav Petkov Cc: linux-pci@vger.kernel.org Link: http://lkml.kernel.org/r/20170316215057.205961140@linutronix.de Signed-off-by: Thomas Gleixner --- drivers/pci/access.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) (limited to 'drivers/pci/access.c') diff --git a/drivers/pci/access.c b/drivers/pci/access.c index c80e37a69305..913d6722ece9 100644 --- a/drivers/pci/access.c +++ b/drivers/pci/access.c @@ -25,6 +25,14 @@ DEFINE_RAW_SPINLOCK(pci_lock); #define PCI_word_BAD (pos & 1) #define PCI_dword_BAD (pos & 3) +#ifdef CONFIG_PCI_LOCKLESS_CONFIG +# define pci_lock_config(f) do { (void)(f); } while (0) +# define pci_unlock_config(f) do { (void)(f); } while (0) +#else +# define pci_lock_config(f) raw_spin_lock_irqsave(&pci_lock, f) +# define pci_unlock_config(f) raw_spin_unlock_irqrestore(&pci_lock, f) +#endif + #define PCI_OP_READ(size, type, len) \ int pci_bus_read_config_##size \ (struct pci_bus *bus, unsigned int devfn, int pos, type *value) \ @@ -33,10 +41,10 @@ int pci_bus_read_config_##size \ unsigned long flags; \ u32 data = 0; \ if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER; \ - raw_spin_lock_irqsave(&pci_lock, flags); \ + pci_lock_config(flags); \ res = bus->ops->read(bus, devfn, pos, len, &data); \ *value = (type)data; \ - raw_spin_unlock_irqrestore(&pci_lock, flags); \ + pci_unlock_config(flags); \ return res; \ } @@ -47,9 +55,9 @@ int pci_bus_write_config_##size \ int res; \ unsigned long flags; \ if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER; \ - raw_spin_lock_irqsave(&pci_lock, flags); \ + pci_lock_config(flags); \ res = bus->ops->write(bus, devfn, pos, len, value); \ - raw_spin_unlock_irqrestore(&pci_lock, flags); \ + pci_unlock_config(flags); \ return res; \ } -- cgit v1.2.3