<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/drivers/base/cpu.c, branch v2.6.35-rc6</title>
<subtitle>Linux kernel for Apalis and Colibri modules</subtitle>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/'/>
<entry>
<title>drivers/base/cpu.c: fix the output from /sys/devices/system/cpu/offline</title>
<updated>2010-05-21T16:37:28+00:00</updated>
<author>
<name>Jan Beulich</name>
<email>JBeulich@novell.com</email>
</author>
<published>2010-04-27T21:01:20+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=cdc6e3d3968052cebb2f2ddcd742bff29fbd1a90'/>
<id>cdc6e3d3968052cebb2f2ddcd742bff29fbd1a90</id>
<content type='text'>
Without CONFIG_CPUMASK_OFFSTACK, simply inverting cpu_online_mask leads
to CPUs beyond nr_cpu_ids to be displayed twice and CPUs not even
possible to be displayed as offline.

Signed-off-by: Jan Beulich &lt;jbeulich@novell.com&gt;
Cc: Andi Kleen &lt;ak@linux.intel.com&gt;
Cc: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Cc: stable &lt;stable@kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Without CONFIG_CPUMASK_OFFSTACK, simply inverting cpu_online_mask leads
to CPUs beyond nr_cpu_ids to be displayed twice and CPUs not even
possible to be displayed as offline.

Signed-off-by: Jan Beulich &lt;jbeulich@novell.com&gt;
Cc: Andi Kleen &lt;ak@linux.intel.com&gt;
Cc: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Cc: stable &lt;stable@kernel.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h</title>
<updated>2010-03-30T13:02:32+00:00</updated>
<author>
<name>Tejun Heo</name>
<email>tj@kernel.org</email>
</author>
<published>2010-03-24T08:04:11+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=5a0e3ad6af8660be21ca98a971cd00f331318c05'/>
<id>5a0e3ad6af8660be21ca98a971cd00f331318c05</id>
<content type='text'>
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 -&gt; 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 &lt;tj@kernel.org&gt;
Guess-its-ok-by: Christoph Lameter &lt;cl@linux-foundation.org&gt;
Cc: Ingo Molnar &lt;mingo@redhat.com&gt;
Cc: Lee Schermerhorn &lt;Lee.Schermerhorn@hp.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
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 -&gt; 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 &lt;tj@kernel.org&gt;
Guess-its-ok-by: Christoph Lameter &lt;cl@linux-foundation.org&gt;
Cc: Ingo Molnar &lt;mingo@redhat.com&gt;
Cc: Lee Schermerhorn &lt;Lee.Schermerhorn@hp.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>sysdev: the cpu probe/release attributes should be sysdev_class_attributes</title>
<updated>2010-03-19T14:12:19+00:00</updated>
<author>
<name>Stephen Rothwell</name>
<email>sfr@canb.auug.org.au</email>
</author>
<published>2010-03-15T23:33:32+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=67fc233f4fb67907861b4077cea5294035f80dc7'/>
<id>67fc233f4fb67907861b4077cea5294035f80dc7</id>
<content type='text'>
This fixes these warnings:

drivers/base/cpu.c:264: warning: initialization from incompatible pointer type
drivers/base/cpu.c:265: warning: initialization from incompatible pointer type

Cc: Andi Kleen &lt;andi@firstfloor.org&gt;
Signed-off-by: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This fixes these warnings:

drivers/base/cpu.c:264: warning: initialization from incompatible pointer type
drivers/base/cpu.c:265: warning: initialization from incompatible pointer type

Cc: Andi Kleen &lt;andi@firstfloor.org&gt;
Signed-off-by: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>sysdev: fix up the probe/release attributes</title>
<updated>2010-03-08T01:04:49+00:00</updated>
<author>
<name>Greg Kroah-Hartman</name>
<email>gregkh@suse.de</email>
</author>
<published>2010-01-21T23:07:59+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=6c1733aca0b48db4d0e660d54976a1cca25b5eaf'/>
<id>6c1733aca0b48db4d0e660d54976a1cca25b5eaf</id>
<content type='text'>
These should be sysdev attributes, not class attributes.  This patch
should resolve the problem.

Thanks to Stephen Rothwell for pointing out the problem.

Reported-by: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Cc: Andi Kleen &lt;andi@firstfloor.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
These should be sysdev attributes, not class attributes.  This patch
should resolve the problem.

Thanks to Stephen Rothwell for pointing out the problem.

Reported-by: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Cc: Andi Kleen &lt;andi@firstfloor.org&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>driver-core: Add attribute argument to class_attribute show/store</title>
<updated>2010-03-08T01:04:48+00:00</updated>
<author>
<name>Andi Kleen</name>
<email>andi@firstfloor.org</email>
</author>
<published>2010-01-05T11:48:07+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=28812fe11a21826ba4c97c6c7971a619987cd912'/>
<id>28812fe11a21826ba4c97c6c7971a619987cd912</id>
<content type='text'>
Passing the attribute to the low level IO functions allows all kinds
of cleanups, by sharing low level IO code without requiring
an own function for every piece of data.

Also drivers can extend the attributes with own data fields
and use that in the low level function.

This makes the class attributes the same as sysdev_class attributes
and plain attributes.

This will allow further cleanups in drivers.

Full tree sweep converting all users.

Signed-off-by: Andi Kleen &lt;ak@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Passing the attribute to the low level IO functions allows all kinds
of cleanups, by sharing low level IO code without requiring
an own function for every piece of data.

Also drivers can extend the attributes with own data fields
and use that in the low level function.

This makes the class attributes the same as sysdev_class attributes
and plain attributes.

This will allow further cleanups in drivers.

Full tree sweep converting all users.

Signed-off-by: Andi Kleen &lt;ak@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>sysdev: Convert node driver</title>
<updated>2010-03-08T01:04:47+00:00</updated>
<author>
<name>Andi Kleen</name>
<email>andi@firstfloor.org</email>
</author>
<published>2010-01-05T11:48:03+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=e1a7e29a266ba3313a873d302b352521403bd155'/>
<id>e1a7e29a266ba3313a873d302b352521403bd155</id>
<content type='text'>
Use sysdev_class attribute arrays in node driver

Convert the node driver to sysdev_class attribute arrays. This
greatly cleans up the code and remove a lot of code.

Signed-off-by: Andi Kleen &lt;ak@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;

</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Use sysdev_class attribute arrays in node driver

Convert the node driver to sysdev_class attribute arrays. This
greatly cleans up the code and remove a lot of code.

Signed-off-by: Andi Kleen &lt;ak@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;

</pre>
</div>
</content>
</entry>
<entry>
<title>sysdev: Convert cpu driver sysdev class attributes</title>
<updated>2010-03-08T01:04:47+00:00</updated>
<author>
<name>Andi Kleen</name>
<email>andi@firstfloor.org</email>
</author>
<published>2010-01-05T11:48:00+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=265d2e2e31c5f6dc1b20ae1653a17fdba706f79e'/>
<id>265d2e2e31c5f6dc1b20ae1653a17fdba706f79e</id>
<content type='text'>
Using the new attribute argument convert the cpu driver class attributes
to carry the node state. Then use a shared function to do what a lot of
individual functions did before.

This eliminates an ugly macro.

Signed-off-by: Andi Kleen &lt;ak@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;


</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Using the new attribute argument convert the cpu driver class attributes
to carry the node state. Then use a shared function to do what a lot of
individual functions did before.

This eliminates an ugly macro.

Signed-off-by: Andi Kleen &lt;ak@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;


</pre>
</div>
</content>
</entry>
<entry>
<title>sysdev: Pass attribute in sysdev_class attributes show/store</title>
<updated>2010-03-08T01:04:47+00:00</updated>
<author>
<name>Andi Kleen</name>
<email>andi@firstfloor.org</email>
</author>
<published>2010-01-05T11:47:58+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=c9be0a36f9bf392a7984473124a67a12964df11f'/>
<id>c9be0a36f9bf392a7984473124a67a12964df11f</id>
<content type='text'>
Passing the attribute to the low level IO functions allows all kinds
of cleanups, by sharing low level IO code without requiring
an own function for every piece of data.

Also drivers can extend the attributes with own data fields
and use that in the low level function.

Similar to sysdev_attributes and normal attributes.

This is a tree-wide sweep, converting everything in one go.

No functional changes in this patch other than passing the new
argument everywhere.

Tested on x86, the non x86 parts are uncompiled.

Signed-off-by: Andi Kleen &lt;ak@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;


</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Passing the attribute to the low level IO functions allows all kinds
of cleanups, by sharing low level IO code without requiring
an own function for every piece of data.

Also drivers can extend the attributes with own data fields
and use that in the low level function.

Similar to sysdev_attributes and normal attributes.

This is a tree-wide sweep, converting everything in one go.

No functional changes in this patch other than passing the new
argument everywhere.

Tested on x86, the non x86 parts are uncompiled.

Signed-off-by: Andi Kleen &lt;ak@linux.intel.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@suse.de&gt;


</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu</title>
<updated>2009-12-14T17:58:24+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2009-12-14T17:58:24+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=d0316554d3586cbea60592a41391b5def2553d6f'/>
<id>d0316554d3586cbea60592a41391b5def2553d6f</id>
<content type='text'>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (34 commits)
  m68k: rename global variable vmalloc_end to m68k_vmalloc_end
  percpu: add missing per_cpu_ptr_to_phys() definition for UP
  percpu: Fix kdump failure if booted with percpu_alloc=page
  percpu: make misc percpu symbols unique
  percpu: make percpu symbols in ia64 unique
  percpu: make percpu symbols in powerpc unique
  percpu: make percpu symbols in x86 unique
  percpu: make percpu symbols in xen unique
  percpu: make percpu symbols in cpufreq unique
  percpu: make percpu symbols in oprofile unique
  percpu: make percpu symbols in tracer unique
  percpu: make percpu symbols under kernel/ and mm/ unique
  percpu: remove some sparse warnings
  percpu: make alloc_percpu() handle array types
  vmalloc: fix use of non-existent percpu variable in put_cpu_var()
  this_cpu: Use this_cpu_xx in trace_functions_graph.c
  this_cpu: Use this_cpu_xx for ftrace
  this_cpu: Use this_cpu_xx in nmi handling
  this_cpu: Use this_cpu operations in RCU
  this_cpu: Use this_cpu ops for VM statistics
  ...

Fix up trivial (famous last words) global per-cpu naming conflicts in
	arch/x86/kvm/svm.c
	mm/slab.c
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (34 commits)
  m68k: rename global variable vmalloc_end to m68k_vmalloc_end
  percpu: add missing per_cpu_ptr_to_phys() definition for UP
  percpu: Fix kdump failure if booted with percpu_alloc=page
  percpu: make misc percpu symbols unique
  percpu: make percpu symbols in ia64 unique
  percpu: make percpu symbols in powerpc unique
  percpu: make percpu symbols in x86 unique
  percpu: make percpu symbols in xen unique
  percpu: make percpu symbols in cpufreq unique
  percpu: make percpu symbols in oprofile unique
  percpu: make percpu symbols in tracer unique
  percpu: make percpu symbols under kernel/ and mm/ unique
  percpu: remove some sparse warnings
  percpu: make alloc_percpu() handle array types
  vmalloc: fix use of non-existent percpu variable in put_cpu_var()
  this_cpu: Use this_cpu_xx in trace_functions_graph.c
  this_cpu: Use this_cpu_xx for ftrace
  this_cpu: Use this_cpu_xx in nmi handling
  this_cpu: Use this_cpu operations in RCU
  this_cpu: Use this_cpu ops for VM statistics
  ...

Fix up trivial (famous last words) global per-cpu naming conflicts in
	arch/x86/kvm/svm.c
	mm/slab.c
</pre>
</div>
</content>
</entry>
<entry>
<title>powerpc/pseries: Serialize cpu hotplug operations during deactivate Vs deallocate</title>
<updated>2009-12-09T06:09:36+00:00</updated>
<author>
<name>Gautham R Shenoy</name>
<email>ego@in.ibm.com</email>
</author>
<published>2009-11-26T09:59:05+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=51badebdcf394cc5fd574a524b55b3f6085e5e9c'/>
<id>51badebdcf394cc5fd574a524b55b3f6085e5e9c</id>
<content type='text'>
Currently the cpu-allocation/deallocation process comprises of two steps:
- Set the indicators and to update the device tree with DLPAR node
  information.

- Online/offline the allocated/deallocated CPU.

This is achieved by writing to the sysfs tunables "probe" during allocation
and "release" during deallocation.

At the sametime, the userspace can independently online/offline the CPUs of
the system using the sysfs tunable "online".

It is quite possible that when a userspace tool offlines a CPU
for the purpose of deallocation and is in the process of updating the device
tree, some other userspace tool could bring the CPU back online by writing to
the "online" sysfs tunable thereby causing the deallocate process to fail.

The solution to this is to serialize writes to the "probe/release" sysfs
tunable with the writes to the "online" sysfs tunable.

This patch employs a mutex to provide this serialization, which is a no-op on
all architectures except PPC_PSERIES

Signed-off-by: Gautham R Shenoy &lt;ego@in.ibm.com&gt;
Acked-by: Vaidyanathan Srinivasan &lt;svaidy@linux.vnet.ibm.com&gt;
Signed-off-by: Benjamin Herrenschmidt &lt;benh@kernel.crashing.org&gt;
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<pre>
Currently the cpu-allocation/deallocation process comprises of two steps:
- Set the indicators and to update the device tree with DLPAR node
  information.

- Online/offline the allocated/deallocated CPU.

This is achieved by writing to the sysfs tunables "probe" during allocation
and "release" during deallocation.

At the sametime, the userspace can independently online/offline the CPUs of
the system using the sysfs tunable "online".

It is quite possible that when a userspace tool offlines a CPU
for the purpose of deallocation and is in the process of updating the device
tree, some other userspace tool could bring the CPU back online by writing to
the "online" sysfs tunable thereby causing the deallocate process to fail.

The solution to this is to serialize writes to the "probe/release" sysfs
tunable with the writes to the "online" sysfs tunable.

This patch employs a mutex to provide this serialization, which is a no-op on
all architectures except PPC_PSERIES

Signed-off-by: Gautham R Shenoy &lt;ego@in.ibm.com&gt;
Acked-by: Vaidyanathan Srinivasan &lt;svaidy@linux.vnet.ibm.com&gt;
Signed-off-by: Benjamin Herrenschmidt &lt;benh@kernel.crashing.org&gt;
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