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
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