linux-toradex.git/arch/x86/kernel/smp.c, branch v3.3.4

x86, reboot: Fix typo in nmi reboot path

2012-01-07T11:19:37+00:00

It was brought to my attention that my x86 change to use NMI in
the reboot path broke Intel Nehalem and Westmere boxes when
using kexec.

I realized I had mistyped the if statement in commit
3603a2512f9e69dc87914ba922eb4a0812b21cd6 and stuck the ')' in
the wrong spot.  Putting it in the right spot fixes kexec again.

Doh.

Reported-by: Yinghai Lu 
Cc: Linus Torvalds 
Signed-off-by: Don Zickus 
Link: http://lkml.kernel.org/r/1325866671-9797-1-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar

x86, NMI: Add knob to disable using NMI IPIs to stop cpus

2011-12-05T11:00:23+00:00

Some machines may exhibit problems using the NMI to stop other
cpus. This knob just allows one to revert back to the original
behaviour to help diagnose the problem.

V2:
  make function static

Signed-off-by: Don Zickus 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Robert Richter 
Cc: seiji.aguchi@hds.com
Cc: vgoyal@redhat.com
Cc: mjg@redhat.com
Cc: tony.luck@intel.com
Cc: gong.chen@intel.com
Cc: satoru.moriya@hds.com
Cc: avi@redhat.com
Cc: Andi Kleen 
Link: http://lkml.kernel.org/r/1318533267-18880-4-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar

x86, reboot: Use NMI instead of REBOOT_VECTOR to stop cpus

2011-12-05T11:00:14+00:00

A recent discussion started talking about the locking on the
pstore fs and how it relates to the kmsg infrastructure.  We
noticed it was possible for userspace to r/w to the pstore fs
(grabbing the locks in the process) and block the panic path
from r/w to the same fs.

The reason was the cpu with the lock could be doing work while
the crashing cpu is panic'ing.  Busting those spinlocks might
cause those cpus to step on each other's data.  Fine, fair
enough.

It was suggested it would be nice to serialize the panic path
(ie stop the other cpus) and have only one cpu running.  This
would allow us to bust the spinlocks and not worry about another
cpu stepping on the data.

Of course, smp_send_stop() does this in the panic case.
kmsg_dump() would have to be moved to be called after it.  Easy
enough.

The only problem is on x86 the smp_send_stop() function calls
the REBOOT_VECTOR.  Any cpu with irqs disabled (which pstore and
its backend ERST would do), block this IPI and thus do not stop.
 This makes it difficult to reliably log data to the pstore fs.

The patch below switches from the REBOOT_VECTOR to NMI (and
mimics what kdump does).  Switching to NMI allows us to deliver
the IPI when irqs are disabled, increasing the reliability of
this function.

However, Andi carefully noted that on some machines this
approach does not work because of broken BIOSes or whatever.

To help accomodate this, the next couple of patches will run a
selftest and provide a knob to disable.

V2:
  uses atomic ops to serialize the cpu that shuts everyone down
V3:
  comment cleanup

Signed-off-by: Don Zickus 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Robert Richter 
Cc: seiji.aguchi@hds.com
Cc: vgoyal@redhat.com
Cc: mjg@redhat.com
Cc: tony.luck@intel.com
Cc: gong.chen@intel.com
Cc: satoru.moriya@hds.com
Cc: avi@redhat.com
Cc: Andi Kleen 
Link: http://lkml.kernel.org/r/1318533267-18880-2-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar

x86: Fix files explicitly requiring export.h for EXPORT_SYMBOL/THIS_MODULE

2011-10-31T23:30:35+00:00

These files were implicitly getting EXPORT_SYMBOL via device.h
which was including module.h, but that will be fixed up shortly.

By fixing these now, we can avoid seeing things like:

arch/x86/kernel/rtc.c:29: warning: type defaults to ‘int’ in declaration of ‘EXPORT_SYMBOL’
arch/x86/kernel/pci-dma.c:20: warning: type defaults to ‘int’ in declaration of ‘EXPORT_SYMBOL’
arch/x86/kernel/e820.c:69: warning: type defaults to ‘int’ in declaration of ‘EXPORT_SYMBOL_GPL’

[ with input from Randy Dunlap  and also
  from Stephen Rothwell  ]

Signed-off-by: Paul Gortmaker

sched: Provide scheduler_ipi() callback in response to smp_send_reschedule()

2011-04-14T06:52:32+00:00

For future rework of try_to_wake_up() we'd like to push part of that
function onto the CPU the task is actually going to run on.

In order to do so we need a generic callback from the existing scheduler IPI.

This patch introduces such a generic callback: scheduler_ipi() and
implements it as a NOP.

BenH notes: PowerPC might use this IPI on offline CPUs under rare conditions!

Acked-by: Russell King 
Acked-by: Martin Schwidefsky 
Acked-by: Chris Metcalf 
Acked-by: Jesper Nilsson 
Acked-by: Benjamin Herrenschmidt 
Signed-off-by: Ralf Baechle 
Reviewed-by: Frank Rowand 
Cc: Mike Galbraith 
Cc: Nick Piggin 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Signed-off-by: Ingo Molnar 
Signed-off-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/20110405152728.744338123@chello.nl

x86, kexec: Make sure to stop all CPUs before exiting the kernel

2010-10-21T20:30:44+00:00

x86 smp_ops now has a new op, stop_other_cpus which takes a parameter
"wait" this allows the caller to specify if it wants to stop until all
the cpus have processed the stop IPI.  This is required specifically
for the kexec case where we should wait for all the cpus to be stopped
before starting the new kernel.  We now wait for the cpus to stop in
all cases except for panic/kdump where we expect things to be broken
and we are doing our best to make things work anyway.

This patch fixes a legitimate regression, which was introduced during
2.6.30, by commit id 4ef702c10b5df18ab04921fc252c26421d4d6c75.

Signed-off-by: Alok N Kataria 
LKML-Reference: <1286833028.1372.20.camel@ank32.eng.vmware.com>
Cc: Eric W. Biederman 
Cc: Jeremy Fitzhardinge 
Cc:  v2.6.30-36
Signed-off-by: H. Peter Anvin

include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h

2010-03-30T13:02:32+00:00

percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files.  percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.

percpu.h -> slab.h dependency is about to be removed.  Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability.  As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.

  http://userweb.kernel.org/~tj/misc/slabh-sweep.py

The script does the followings.

* Scan files for gfp and slab usages and update includes such that
  only the necessary includes are there.  ie. if only gfp is used,
  gfp.h, if slab is used, slab.h.

* When the script inserts a new include, it looks at the include
  blocks and try to put the new include such that its order conforms
  to its surrounding.  It's put in the include block which contains
  core kernel includes, in the same order that the rest are ordered -
  alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
  doesn't seem to be any matching order.

* If the script can't find a place to put a new include (mostly
  because the file doesn't have fitting include block), it prints out
  an error message indicating which .h file needs to be added to the
  file.

The conversion was done in the following steps.

1. The initial automatic conversion of all .c files updated slightly
   over 4000 files, deleting around 700 includes and adding ~480 gfp.h
   and ~3000 slab.h inclusions.  The script emitted errors for ~400
   files.

2. Each error was manually checked.  Some didn't need the inclusion,
   some needed manual addition while adding it to implementation .h or
   embedding .c file was more appropriate for others.  This step added
   inclusions to around 150 files.

3. The script was run again and the output was compared to the edits
   from #2 to make sure no file was left behind.

4. Several build tests were done and a couple of problems were fixed.
   e.g. lib/decompress_*.c used malloc/free() wrappers around slab
   APIs requiring slab.h to be added manually.

5. The script was run on all .h files but without automatically
   editing them as sprinkling gfp.h and slab.h inclusions around .h
   files could easily lead to inclusion dependency hell.  Most gfp.h
   inclusion directives were ignored as stuff from gfp.h was usually
   wildly available and often used in preprocessor macros.  Each
   slab.h inclusion directive was examined and added manually as
   necessary.

6. percpu.h was updated not to include slab.h.

7. Build test were done on the following configurations and failures
   were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
   distributed build env didn't work with gcov compiles) and a few
   more options had to be turned off depending on archs to make things
   build (like ipr on powerpc/64 which failed due to missing writeq).

   * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
   * powerpc and powerpc64 SMP allmodconfig
   * sparc and sparc64 SMP allmodconfig
   * ia64 SMP allmodconfig
   * s390 SMP allmodconfig
   * alpha SMP allmodconfig
   * um on x86_64 SMP allmodconfig

8. percpu.h modifications were reverted so that it could be applied as
   a separate patch and serve as bisection point.

Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.

Signed-off-by: Tejun Heo 
Guess-its-ok-by: Christoph Lameter 
Cc: Ingo Molnar 
Cc: Lee Schermerhorn

Revert "x86, timers: Check for pending timers after (device) interrupts"

2009-10-09T13:58:20+00:00

This reverts commit 9bcbdd9c58617f1301dd4f17c738bb9bc73aca70.

The real bug producing LatencyTop latencies has been fixed in:

  f5dc375: sched: Update the clock of runqueue select_task_rq() selected

And the commit being reverted here triggers local timer processing
from every device IRQ. If device IRQs come in at a high frequency,
this could cause a performance regression.

The commit being reverted here purely 'fixed' the reported latency
as a side effect, because CPUs were being moved out of idle more
often.

Acked-by: Peter Zijlstra 
Cc: Arjan van de Ven 
Cc: Frans Pop 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Thomas Gleixner 
LKML-Reference: <20091008064041.67219b13@infradead.org>
Signed-off-by: Ingo Molnar

x86, timers: Check for pending timers after (device) interrupts

2009-10-08T15:27:27+00:00

Now that range timers and deferred timers are common, I found a
problem with these using the "perf timechart" tool. Frans Pop also
reported high scheduler latencies via LatencyTop, when using
iwlagn.

It turns out that on x86, these two 'opportunistic' timers only get
checked when another "real" timer happens. These opportunistic
timers have the objective to save power by hitchhiking on other
wakeups, as to avoid CPU wakeups by themselves as much as possible.

The change in this patch runs this check not only at timer
interrupts, but at all (device) interrupts. The effect is that:

 1) the deferred timers/range timers get delayed less

 2) the range timers cause less wakeups by themselves because
    the percentage of hitchhiking on existing wakeup events goes up.

I've verified the working of the patch using "perf timechart", the
original exposed bug is gone with this patch. Frans also reported
success - the latencies are now down in the expected ~10 msec
range.

Signed-off-by: Arjan van de Ven 
Tested-by: Frans Pop 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Mike Galbraith 
LKML-Reference: <20091008064041.67219b13@infradead.org>
Signed-off-by: Ingo Molnar

Merge branch 'linus' into x86/mce3

2009-06-11T21:31:52+00:00

Conflicts:
	arch/x86/kernel/cpu/mcheck/mce_64.c
	arch/x86/kernel/irq.c

Merge reason: Resolve the conflicts above.

Signed-off-by: Ingo Molnar