From 7ea7e98fd8d02351c43ef4ab35d70f3aaa26c31d Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Thu, 19 Oct 2006 09:41:28 -0600 Subject: [PATCH] PCI: Block on access to temporarily unavailable pci device The existing implementation of pci_block_user_cfg_access() was recently criticised for providing out of date information and for returning errors on write, which applications won't be expecting. This reimplementation uses a global wait queue and a bit per device. I've open-coded prepare_to_wait() / finish_wait() as I could optimise it significantly by knowing that the pci_lock protected us at all points. It looked a bit funny to be doing a spin_unlock_irqsave(); schedule(), so I used spin_lock_irq() for the _user versions of pci_read_config and pci_write_config. Not carrying a flags pointer around made the code much less nasty. Attempts to block an already blocked device hit a BUG() and attempts to unblock an already unblocked device hit a WARN(). If we need to block access to a device from userspace, it's because it's unsafe for even another bit of the kernel to access the device. An attempt to block a device for a second time means we're about to access the device to perform some other operation, which could provoke undefined behaviour from the device. Signed-off-by: Matthew Wilcox Acked-by: Adam Belay Acked-by: Alan Cox Signed-off-by: Greg Kroah-Hartman --- Reading git-format-patch failed