1. 18 11月, 2016 1 次提交
    • L
      PCI: Don't acquire ref on parent in pci_bridge_d3_update() · 738a7edb
      Lukas Wunner 提交于
      This function is always called with an existing pci_dev struct, which
      holds a reference on the pci_bus struct it resides on, which in turn
      holds a reference on pci_bus->bridge, which is the pci_dev's parent.
      
      Hence there's no need to acquire an additional ref on the parent.
      
      More specifically, the pci_dev exists until pci_destroy_dev() drops the
      final reference on it, so all calls to pci_bridge_d3_update() must be
      finished before that.  It is arguably the caller's responsibility to ensure
      that it doesn't call pci_bridge_d3_update() with a pci_dev that might
      suddenly disappear, but in any case the existing callers are all safe:
      
      - The call in pci_destroy_dev() happens before the call to put_device().
      - The call in pci_bus_add_device() is synchronized with pci_destroy_dev()
        using pci_lock_rescan_remove().
      - The calls to pci_d3cold_disable() from the xhci and nouveau drivers
        are safe because a ref on the pci_dev is held as long as it's bound to
        a driver.
      - The calls to pci_d3cold_enable() / pci_d3cold_disable() when modifying
        the sysfs "d3cold_allowed" entry are also safe because kernfs_drain()
        waits for existing sysfs users to finish before removing the entry,
        and pci_destroy_dev() is called way after that.
      
      No functional change intended.
      Tested-by: NMika Westerberg <mika.westerberg@linux.intel.com>
      Signed-off-by: NLukas Wunner <lukas@wunner.de>
      Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
      Reviewed-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      738a7edb
  2. 12 11月, 2016 2 次提交
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