kernel news – 02.12.2012

Posted: December 3, 2012 in kernel

-Tejun Heo has workqueue last-minute fixes for -rc7:

Unfortunately, I have two really late fixes. One was for a
long-standing bug and queued for 3.8 but I found out about a
regression introduced during 3.7-rc1 two days ago, so I’m sending out
the two fixes together.

The first (long-standing) one is rescuer_thread() entering exit path
w/ TASK_INTERRUPTIBLE. It only triggers on workqueue destructions
which isn’t very frequent and the exit path can usually survive being
called with TASK_INTERRUPT, so it was hidden pretty well. Apparently,
if you’re reiserfs, this could lead to the exiting kthread sleeping
indefinitely holding a mutex, which is never good. The fix is simple
– restoring TASK_RUNNING before returning from the kthread function.

The second one is introduced by the new mod_delayed_work().
mod_delayed_work() was missing special case handling for 0 delay.
Instead of queueing the work item immediately, it queued the timer
which expires on the closest next tick. Some users of the new
function converted from “[__]cancel_delayed_work() +
queue_delayed_work()” combination became unhappy with the extra delay.
Block unplugging led to noticeably higher number of context switches
and intel 6250 wireless failed to associate with WPA-Enterprise
network. The fix, again, is fairly simple. The 0 delay special case
logic from queue_delayed_work_on() should be moved to
__queue_delayed_work() which is shared by both queue_delayed_work_on()
and mod_delayed_work_on().

The first one is difficult to trigger and the failure mode for the
latter isn’t completely catastrophic, so missing these two for 3.7
wouldn’t make it a disastrous release, but both bugs are nasty and the
fixes are fairly safe, so please consider pulling the following
branch.

git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-3.7-fixes

-David Miller and some networking updates:

1) 8139cp leaks memory in error paths, from Francois Romieu.

2) do_tcp_sendpages() cannot handle order > 0 pages, but they can
certainly arrive there now, fix from Eric Dumazet.

3) Race condition and sysfs fixes in bonding from Nikolay Aleksandrov.

4) Remain-on-Channel fix in mac80211 from Felix Liao.

5) CCK rate calculation fix in iwlwifi, from Emmanuel Grumbach.

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