linux-toradex.git/kernel, branch v3.2.14-rt24

kconfig-preempt-rt-full.patch

2012-04-10T21:37:38+00:00

Signed-off-by: Thomas Gleixner

cpu: Make hotplug.lock a "sleeping" spinlock on RT

2012-04-10T21:37:37+00:00

Tasks can block on hotplug.lock in pin_current_cpu(), but their state
might be != RUNNING. So the mutex wakeup will set the state
unconditionally to RUNNING. That might cause spurious unexpected
wakeups. We could provide a state preserving mutex_lock() function,
but this is semantically backwards. So instead we convert the
hotplug.lock() to a spinlock for RT, which has the state preserving
semantics already.

Signed-off-by: Steven Rostedt 
Cc: Carsten Emde 
Cc: John Kacur 
Cc: Peter Zijlstra 
Cc: Clark Williams 
Cc: stable-rt@vger.kernel.org
Link: http://lkml.kernel.org/r/1330702617.25686.265.camel@gandalf.stny.rr.com
Signed-off-by: Thomas Gleixner

sched/rt: Fix wait_task_interactive() to test rt_spin_lock state

2012-04-10T21:37:36+00:00

The wait_task_interactive() will have a task sleep waiting for another
task to have a certain state. But it ignores the rt_spin_locks state
and can return with an incorrect result if the task it is waiting
for is blocked on a rt_spin_lock() and is waking up.

The rt_spin_locks save the tasks state in the saved_state field
and the wait_task_interactive() must also test that state.

Signed-off-by: Steven Rostedt 
Cc: Carsten Emde 
Cc: John Kacur 
Cc: Peter Zijlstra 
Cc: Clark Williams 
Cc: stable-rt@vger.kernel.org
Link: http://lkml.kernel.org/r/20120301190345.979435764@goodmis.org
Signed-off-by: Thomas Gleixner

ring-buffer/rt: Check for irqs disabled before grabbing reader lock

2012-04-10T21:37:35+00:00

In RT the reader lock is a mutex and we can not grab it when preemption is
disabled. The in_atomic() check that is there does not check if irqs are
disabled. Add that check as well.

Signed-off-by: Steven Rostedt 
Cc: Carsten Emde 
Cc: John Kacur 
Cc: Peter Zijlstra 
Cc: Clark Williams 
Cc: stable-rt@vger.kernel.org
Link: http://lkml.kernel.org/r/20120301190345.786365803@goodmis.org
Signed-off-by: Thomas Gleixner

futex/rt: Fix possible lockup when taking pi_lock in proxy handler

2012-04-10T21:37:35+00:00

When taking the pi_lock, we must disable interrupts because the
pi_lock can also be taken in an interrupt handler.

Use raw_spin_lock_irq() instead of raw_spin_lock().

Signed-off-by: Steven Rostedt 
Cc: Carsten Emde 
Cc: John Kacur 
Cc: Peter Zijlstra 
Cc: Clark Williams 
Cc: stable-rt@vger.kernel.org
Link: http://lkml.kernel.org/r/20120301190345.165160680@goodmis.org
Signed-off-by: Thomas Gleixner

timer: Fix hotplug for -rt

2012-04-10T21:37:34+00:00

Revert the RT patch:
    Author: Ingo Molnar 
    Date:   Fri Jul 3 08:30:32 2009 -0500
    timers: fix timer hotplug on -rt

    Here we are in the CPU_DEAD notifier, and we must not sleep nor
    enable interrupts.

There's no problem with sleeping in this notifier.

But the get_cpu_var() had to be converted to a get_local_var().

Replace the previous fix with the get_local_var() convert.

Signed-off-by: Steven Rostedt 
Cc: Carsten Emde 
Cc: John Kacur 
Cc: Peter Zijlstra 
Cc: Clark Williams 
Cc: stable-rt@vger.kernel.org
Link: http://lkml.kernel.org/r/20120301190344.948157137@goodmis.org
Signed-off-by: Thomas Gleixner

sysrq: Allow immediate Magic SysRq output for PREEMPT_RT_FULL

2012-04-10T21:37:32+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

add /sys/kernel/realtime entry

2012-04-10T21:37:31+00:00

Add a /sys/kernel entry to indicate that the kernel is a
realtime kernel.

Clark says that he needs this for udev rules, udev needs to evaluate
if its a PREEMPT_RT kernel a few thousand times and parsing uname
output is too slow or so.

Are there better solutions? Should it exist and return 0 on !-rt?

Signed-off-by: Clark Williams 
Signed-off-by: Peter Zijlstra

kgdb/serial: Short term workaround

2012-04-10T21:37:31+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.

printk: Disable migration instead of preemption

2012-04-10T21:37:29+00:00

There is no need do disable preemption in vprintk(), disable_migrate()
is sufficient. This fixes the following bug in -rt:

[   14.759233] BUG: sleeping function called from invalid context
at /home/rw/linux-rt/kernel/rtmutex.c:645
[   14.759235] in_atomic(): 1, irqs_disabled(): 0, pid: 547, name: bash
[   14.759244] Pid: 547, comm: bash Not tainted 3.0.12-rt29+ #3
[   14.759246] Call Trace:
[   14.759301]  [] __might_sleep+0xeb/0xf0
[   14.759318]  [] rt_spin_lock_fastlock.constprop.9+0x21/0x43
[   14.759336]  [] rt_spin_lock+0xe/0x10
[   14.759354]  [] serial8250_console_write+0x81/0x121
[   14.759366]  [] __call_console_drivers+0x7c/0x93
[   14.759369]  [] _call_console_drivers+0x5c/0x60
[   14.759372]  [] console_unlock+0x147/0x1a2
[   14.759374]  [] vprintk+0x3ea/0x462
[   14.759383]  [] printk+0x51/0x53
[   14.759399]  [] ? proc_reg_poll+0x9a/0x9a
[   14.759403]  [] __handle_sysrq+0x50/0x14d
[   14.759406]  [] write_sysrq_trigger+0x4b/0x53
[   14.759408]  [] ? __handle_sysrq+0x14d/0x14d
[   14.759410]  [] proc_reg_write+0x9f/0xbe
[   14.759426]  [] vfs_write+0xac/0xf3
[   14.759429]  [] ? fget_light+0x3a/0x9b
[   14.759431]  [] sys_write+0x4a/0x6e
[   14.759438]  [] system_call_fastpath+0x16/0x1b

Signed-off-by: Richard Weinberger 
Link: http://lkml.kernel.org/r/1323696956-11445-1-git-send-email-rw@linutronix.de
Signed-off-by: Thomas Gleixner