Red Hat Bugzilla – Bug 618114
Kernel panic on reading from /proc/bus/pci/XX/YY while hot-removing the device.
Last modified: 2011-09-13 08:36:18 EDT
Description of problem:
When we read from a /proc/bus/pci/XX/YY file while hot-removing the device that relates to this file, kernel panics with the following call trace.
Version-Release number of selected component (if applicable):
kernel-2.6.18-208.el5 and earlier.
Steps to Reproduce:
1. Open /proc/bus/pci/XX/YY file
2. remove a pci device with pci hotplug capabilities.
3. Read from the proc file.
Device to be released, pci bus to continue working.
Accepted in linux-next branch, not in mainline yet.
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux maintenance release. Product Management has requested
further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed
products. This request is not yet committed for inclusion in an Update
Wade, could you please include panic call trace? It's missing in the description.
You can download this test kernel from http://people.redhat.com/jwilson/el5
Detailed testing feedback is always welcomed.
*** Bug 648378 has been marked as a duplicate of this bug. ***
As M Yamazaki stated, this wasn't enough to solve the problem (it did solve my simulated pci hotplug bug) but it requires additional protection from the upstream patch, I'm going to attach the patch, but awaiting feedback from our partners on if its sane and working for them.
Looks like there needs to be additional changes, this patch did fix my original problem but there is more..
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.
This bug was part of the RHEL 5.6 kernel advisory and is associated with a patch in 5.6.
It has been returned to CLOSED/ERRATA status against 5.6, and will be cloned for handling further issues in RHEL 5.7.
Please address additional concerns in that bug and not this one.
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.
When reading a file from a subdirectory in /proc/bus/pci/ while hot-unplugging the device related to that file, the system will crash. Now, the kernel correctly handles the simultaneous removal of a device and access to the representation of that device in the proc file system.