On Tue, Jul 03, 2018 at 02:35:41PM +0530, Hari Vyas wrote: > When a pci device is detected, a variable is_added is set to > 1 in pci device structure and proc, sys entries are created. > > When a pci device is removed, first is_added is checked for one > and then device is detached with clearing of proc and sys > entries and at end, is_added is set to 0. > > is_added and is_busmaster are bit fields in pci_dev structure > sharing same memory location. > > A strange issue was observed with multiple times removal and > rescan of a pcie nvme device using sysfs commands where is_added > flag was observed as zero instead of one while removing device > and proc,sys entries are not cleared. This causes issue in > later device addition with warning message "proc_dir_entry" > already registered. > > Debugging revealed a race condition between pcie core driver > enabling is_added bit(pci_bus_add_device()) and nvme driver > reset work-queue enabling is_busmaster bit (by pci_set_master()). > As both fields are not handled in atomic manner and that clears > is_added bit. > > Fix moves device addition is_added bit to separate private flag > variable and use different atomic functions to set and retrieve > device addition state. As is_added shares different memory > location so race condition is avoided. If/when you post a v4 of this, can you include the bugzilla URL right here, i.e., Link: https://bugzilla.kernel.org/show_bug.cgi?id=200283 > Signed-off-by: Hari Vyas <hari.vyas@xxxxxxxxxxxx> That way we can connect the commit with the bugzilla, which contains more information that may be useful in the future. Bjorn
