linux-toradex.git/include/linux, branch v3.2-rt10

wait-simple: Simple waitqueue implementation

2012-01-16T19:00:36+00:00

wait_queue is a swiss army knife and in most of the cases the
complexity is not needed. For RT waitqueues are a constant source of
trouble as we can't convert the head lock to a raw spinlock due to
fancy and long lasting callbacks.

Provide a slim version, which allows RT to replace wait queues. This
should go mainline as well, as it lowers memory consumption and
runtime overhead.

Signed-off-by: Thomas Gleixner

sysrq: Allow immediate Magic SysRq output for PREEMPT_RT_FULL

2012-01-16T19:00:36+00:00

Add a CONFIG option to allow the output from Magic SysRq to be output
immediately, even if this causes large latencies.

If PREEMPT_RT_FULL, printk() will not try to acquire the console lock
when interrupts or preemption are disabled.  If the console lock is
not acquired the printk() output will be buffered, but will not be
output immediately. Some drivers call into the Magic SysRq code
with interrupts or preemption disabled, so the output of Magic SysRq
will be buffered instead of printing immediately if this option is
not selected.

Even with this option selected, Magic SysRq output will be delayed
if the attempt to acquire the console lock fails.

Signed-off-by: Frank Rowand 
Link: http://lkml.kernel.org/r/4E7CEF60.5020508@am.sony.com
Signed-off-by: Thomas Gleixner

mm, rt: kmap_atomic scheduling

2012-01-16T19:00:35+00:00

In fact, with migrate_disable() existing one could play games with
kmap_atomic. You could save/restore the kmap_atomic slots on context
switch (if there are any in use of course), this should be esp easy now
that we have a kmap_atomic stack.

Something like the below.. it wants replacing all the preempt_disable()
stuff with pagefault_disable() && migrate_disable() of course, but then
you can flip kmaps around like below.

Signed-off-by: Peter Zijlstra 
[dvhart@linux.intel.com: build fix]
Link: http://lkml.kernel.org/r/1311842631.5890.208.camel@twins

kgdb/serial: Short term workaround

2012-01-16T19:00:35+00:00

On 07/27/2011 04:37 PM, Thomas Gleixner wrote:
>  - KGDB (not yet disabled) is reportedly unusable on -rt right now due
>    to missing hacks in the console locking which I dropped on purpose.
>

To work around this in the short term you can use this patch, in
addition to the clocksource watchdog patch that Thomas brewed up.

Comments are welcome of course.  Ultimately the right solution is to
change separation between the console and the HW to have a polled mode
+ work queue so as not to introduce any kind of latency.

Thanks,
Jason.

skbufhead-raw-lock.patch

2012-01-16T19:00:33+00:00

Signed-off-by: Thomas Gleixner

jump-label-rt.patch

2012-01-16T19:00:33+00:00

Signed-off-by: Thomas Gleixner

workqueue: Fix cpuhotplug trainwreck

2012-01-16T19:00:32+00:00

The current workqueue code does crazy stuff on cpu unplug, it relies on
forced affine breakage, thereby violating per-cpu expectations. Worse,
it tries to re-attach to a cpu if the thing comes up again before all
previously queued works are finished. This breaks (admittedly bonkers)
cpu-hotplug use that relies on a down-up cycle to push all usage away.

Introduce a new WQ_NON_AFFINE flag that indicates a per-cpu workqueue
will not respect cpu affinity and use this to migrate all its pending
works to whatever cpu is doing cpu-down.

This also adds a warning for queue_on_cpu() users which warns when its
used on WQ_NON_AFFINE workqueues for the API implies you care about
what cpu things are ran on when such workqueues cannot guarantee this.

For the rest, simply flush all per-cpu works and don't mess about.
This also means that currently all workqueues that are manually
flushing things on cpu-down in order to provide the per-cpu guarantee
no longer need to do so.

In short, we tell the WQ what we want it to do, provide validation for
this and loose ~250 lines of code.

Signed-off-by: Peter Zijlstra 
Signed-off-by: Thomas Gleixner

lglocks-rt.patch

2012-01-16T19:00:30+00:00

Signed-off-by: Thomas Gleixner

rcu: Make ksoftirqd do RCU quiescent states

2012-01-16T19:00:30+00:00

Implementing RCU-bh in terms of RCU-preempt makes the system vulnerable
to network-based denial-of-service attacks.  This patch therefore
makes __do_softirq() invoke rcu_bh_qs(), but only when __do_softirq()
is running in ksoftirqd context.  A wrapper layer in interposed so that
other calls to __do_softirq() avoid invoking rcu_bh_qs().  The underlying
function __do_softirq_common() does the actual work.

The reason that rcu_bh_qs() is bad in these non-ksoftirqd contexts is
that there might be a local_bh_enable() inside an RCU-preempt read-side
critical section.  This local_bh_enable() can invoke __do_softirq()
directly, so if __do_softirq() were to invoke rcu_bh_qs() (which just
calls rcu_preempt_qs() in the PREEMPT_RT_FULL case), there would be
an illegal RCU-preempt quiescent state in the middle of an RCU-preempt
read-side critical section.  Therefore, quiescent states can only happen
in cases where __do_softirq() is invoked directly from ksoftirqd.

Signed-off-by: Paul E. McKenney 
Link: http://lkml.kernel.org/r/20111005184518.GA21601@linux.vnet.ibm.com
Signed-off-by: Thomas Gleixner

rcu: Fix macro substitution for synchronize_rcu_bh() on RT

2012-01-16T19:00:30+00:00

kernel/rcutorture.c:492: error: ‘synchronize_rcu_bh’ undeclared here (not in a function)

synchronize_rcu_bh() is not just called as a normal function, but can
also be referenced as a function pointer. When CONFIG_PREEMPT_RT_FULL
is enabled, synchronize_rcu_bh() is defined as synchronize_rcu(), but
needs to be defined without the parenthesis because the compiler will
complain when synchronize_rcu_bh is referenced as a function pointer
and not a function.

Signed-off-by: John Kacur 
Cc: Paul McKenney 
Cc: stable-rt@vger.kernel.org
Link: http://lkml.kernel.org/r/1321235083-21756-1-git-send-email-jkacur@redhat.com
Signed-off-by: Thomas Gleixner