We are pleased to announce the next update to our new preempt-rt series.

- fix the network live lock issue for real

- disable preemption across iomap atomic section

- indentify false positives in the softirq pending check in the nohz code.

The network issue which I described in the -21 release still persists between net-rx and net-tx softirqs. The real fix is replacing the spin_trylock with spin_lock in the affected drivers.

On -rt we had several unexplained reports of cpus going idle with a pending softirq. I got hands on a trace of such a situation. What happens is that a softirq is blocked on a lock which is held by a task which is either blocked itself or running on another CPU. When there is no other active task on the CPU then it goes idle but the softirq pending bit of the blocked softirq thread is still set. This leads to false positive warnings. To filter out those cases the blocked state of the softirq needs to be checked instead of printing the warning blindly.

Download locations:

http://rt.et.redhat.com/download/ http://www.kernel.org/pub/linux/kernel/projects/rt/

Information on the RT patch can be found at:

http://rt.wiki.kernel.org/index.php/Main_Page

to build the 2.6.29.5-rt22 tree, the following patches should be applied:

http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.29.5.tar.bz2 http://www.kernel.org/pub/linux/kernel/projects/rt/patch-2.6.29.5-rt22.bz2

The broken out patches are also available at the same download locations.

Enjoy !

tglx