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[Bug 1526811] Re: SRU: walker list corruption while being intensively stressed

To: kernel-packages@xxxxxxxxxxxxxxxxxxx
From: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
Date: Wed, 13 Jan 2016 23:30:17 -0000
Reply-to: Bug 1526811 <1526811@xxxxxxxxxxxxxxxxxx>
Sender: bounces@xxxxxxxxxxxxx

This bug is awaiting verification that the kernel in -proposed solves
the problem. Please test the kernel and update this bug with the
results. If the problem is solved, change the tag 'verification-needed-
wily' to 'verification-done-wily'.

If verification is not done by 5 working days from today, this fix will
be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how
to enable and use -proposed. Thank you!


** Tags added: verification-needed-wily

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https://bugs.launchpad.net/bugs/1526811

Title:
  SRU: walker list corruption while being intensively stressed

Status in linux package in Ubuntu:
  Fix Committed
Status in linux source package in Wily:
  Fix Committed
Status in linux source package in Xenial:
  Fix Committed

Bug description:
  [SRU Justification][Wily]  + [Xenial]

  While stress testing with the stress-ng procfs stressor I hit a walker
  list bug.  This has been recently fixed by Herbert Xu in commit:

  The commit ba7c95ea3870fe7b847466d39a049ab6f156aa2c ("rhashtable: Fix
  sleeping inside RCU critical section in walk_stop") introduced a new
  spinlock for the walker list.  However, it did not convert all
  existing users of the list over to the new spin lock.  Some continued
  to use the old mutex for this purpose.  This obviously led to
  corruption of the list.

  [Fix]
  Clean upstream cherry pick, commit c6ff5268293ef98e48a99597e765ffc417e39fa5
  Will land in Xenial automatically (4.4)

  
  [Testcase]
  Run multiple instances of the attached code on a multicore system.  Alternatively, run stress-ng --procfs 0 on a multi-core system

  Fix will stop the above code corrupting the list and crashing.

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