<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/lib, branch v3.1-rc2</title>
<subtitle>Linux kernel source tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/'/>
<entry>
<title>Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net</title>
<updated>2011-08-07T05:12:37+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2011-08-07T05:12:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=7cd4767e696123cdb7447fbd7c281eb8c610c8e4'/>
<id>7cd4767e696123cdb7447fbd7c281eb8c610c8e4</id>
<content type='text'>
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net:
  net: Compute protocol sequence numbers and fragment IDs using MD5.
  crypto: Move md5_transform to lib/md5.c
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net:
  net: Compute protocol sequence numbers and fragment IDs using MD5.
  crypto: Move md5_transform to lib/md5.c
</pre>
</div>
</content>
</entry>
<entry>
<title>crypto: Move md5_transform to lib/md5.c</title>
<updated>2011-08-07T01:32:45+00:00</updated>
<author>
<name>David S. Miller</name>
<email>davem@davemloft.net</email>
</author>
<published>2011-08-04T02:45:10+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=bc0b96b54a21246e377122d54569eef71cec535f'/>
<id>bc0b96b54a21246e377122d54569eef71cec535f</id>
<content type='text'>
We are going to use this for TCP/IP sequence number and fragment ID
generation.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
We are going to use this for TCP/IP sequence number and fragment ID
generation.

Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>lib/sha1: use the git implementation of SHA-1</title>
<updated>2011-08-06T18:26:52+00:00</updated>
<author>
<name>Mandeep Singh Baines</name>
<email>msb@chromium.org</email>
</author>
<published>2011-08-06T01:46:27+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=1eb19a12bd2214cdcad5273d472b062a4ba97fa1'/>
<id>1eb19a12bd2214cdcad5273d472b062a4ba97fa1</id>
<content type='text'>
For ChromiumOS, we use SHA-1 to verify the integrity of the root
filesystem.  The speed of the kernel sha-1 implementation has a major
impact on our boot performance.

To improve boot performance, we investigated using the heavily optimized
sha-1 implementation used in git.  With the git sha-1 implementation, we
see a 11.7% improvement in boot time.

10 reboots, remove slowest/fastest.

Before:

  Mean: 6.58 seconds Stdev: 0.14

After (with git sha-1, this patch):

  Mean: 5.89 seconds Stdev: 0.07

The other cool thing about the git SHA-1 implementation is that it only
needs 64 bytes of stack for the workspace while the original kernel
implementation needed 320 bytes.

Signed-off-by: Mandeep Singh Baines &lt;msb@chromium.org&gt;
Cc: Ramsay Jones &lt;ramsay@ramsay1.demon.co.uk&gt;
Cc: Nicolas Pitre &lt;nico@cam.org&gt;
Cc: Herbert Xu &lt;herbert@gondor.apana.org.au&gt;
Cc: David S. Miller &lt;davem@davemloft.net&gt;
Cc: linux-crypto@vger.kernel.org
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
For ChromiumOS, we use SHA-1 to verify the integrity of the root
filesystem.  The speed of the kernel sha-1 implementation has a major
impact on our boot performance.

To improve boot performance, we investigated using the heavily optimized
sha-1 implementation used in git.  With the git sha-1 implementation, we
see a 11.7% improvement in boot time.

10 reboots, remove slowest/fastest.

Before:

  Mean: 6.58 seconds Stdev: 0.14

After (with git sha-1, this patch):

  Mean: 5.89 seconds Stdev: 0.07

The other cool thing about the git SHA-1 implementation is that it only
needs 64 bytes of stack for the workspace while the original kernel
implementation needed 320 bytes.

Signed-off-by: Mandeep Singh Baines &lt;msb@chromium.org&gt;
Cc: Ramsay Jones &lt;ramsay@ramsay1.demon.co.uk&gt;
Cc: Nicolas Pitre &lt;nico@cam.org&gt;
Cc: Herbert Xu &lt;herbert@gondor.apana.org.au&gt;
Cc: David S. Miller &lt;davem@davemloft.net&gt;
Cc: linux-crypto@vger.kernel.org
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'apei-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6</title>
<updated>2011-08-04T07:53:27+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2011-08-04T07:53:27+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=c0c770e610cc4cdcd66c7e939bdf89cc3e72f79d'/>
<id>c0c770e610cc4cdcd66c7e939bdf89cc3e72f79d</id>
<content type='text'>
* 'apei-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6:
  ACPI, APEI, EINJ Param support is disabled by default
  APEI GHES: 32-bit buildfix
  ACPI: APEI build fix
  ACPI, APEI, GHES: Add hardware memory error recovery support
  HWPoison: add memory_failure_queue()
  ACPI, APEI, GHES, Error records content based throttle
  ACPI, APEI, GHES, printk support for recoverable error via NMI
  lib, Make gen_pool memory allocator lockless
  lib, Add lock-less NULL terminated single list
  Add Kconfig option ARCH_HAVE_NMI_SAFE_CMPXCHG
  ACPI, APEI, Add WHEA _OSC support
  ACPI, APEI, Add APEI bit support in generic _OSC call
  ACPI, APEI, GHES, Support disable GHES at boot time
  ACPI, APEI, GHES, Prevent GHES to be built as module
  ACPI, APEI, Use apei_exec_run_optional in APEI EINJ and ERST
  ACPI, APEI, Add apei_exec_run_optional
  ACPI, APEI, GHES, Do not ratelimit fatal error printk before panic
  ACPI, APEI, ERST, Fix erst-dbg long record reading issue
  ACPI, APEI, ERST, Prevent erst_dbg from loading if ERST is disabled
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
* 'apei-release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux-acpi-2.6:
  ACPI, APEI, EINJ Param support is disabled by default
  APEI GHES: 32-bit buildfix
  ACPI: APEI build fix
  ACPI, APEI, GHES: Add hardware memory error recovery support
  HWPoison: add memory_failure_queue()
  ACPI, APEI, GHES, Error records content based throttle
  ACPI, APEI, GHES, printk support for recoverable error via NMI
  lib, Make gen_pool memory allocator lockless
  lib, Add lock-less NULL terminated single list
  Add Kconfig option ARCH_HAVE_NMI_SAFE_CMPXCHG
  ACPI, APEI, Add WHEA _OSC support
  ACPI, APEI, Add APEI bit support in generic _OSC call
  ACPI, APEI, GHES, Support disable GHES at boot time
  ACPI, APEI, GHES, Prevent GHES to be built as module
  ACPI, APEI, Use apei_exec_run_optional in APEI EINJ and ERST
  ACPI, APEI, Add apei_exec_run_optional
  ACPI, APEI, GHES, Do not ratelimit fatal error printk before panic
  ACPI, APEI, ERST, Fix erst-dbg long record reading issue
  ACPI, APEI, ERST, Prevent erst_dbg from loading if ERST is disabled
</pre>
</div>
</content>
</entry>
<entry>
<title>tmpfs radix_tree: locate_item to speed up swapoff</title>
<updated>2011-08-04T00:25:24+00:00</updated>
<author>
<name>Hugh Dickins</name>
<email>hughd@google.com</email>
</author>
<published>2011-08-03T23:21:27+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=e504f3fdd63d486d45b18009e5a65f2e329acb0a'/>
<id>e504f3fdd63d486d45b18009e5a65f2e329acb0a</id>
<content type='text'>
We have already acknowledged that swapoff of a tmpfs file is slower than
it was before conversion to the generic radix_tree: a little slower
there will be acceptable, if the hotter paths are faster.

But it was a shock to find swapoff of a 500MB file 20 times slower on my
laptop, taking 10 minutes; and at that rate it significantly slows down
my testing.

Now, most of that turned out to be overhead from PROVE_LOCKING and
PROVE_RCU: without those it was only 4 times slower than before; and
more realistic tests on other machines don't fare as badly.

I've tried a number of things to improve it, including tagging the swap
entries, then doing lookup by tag: I'd expected that to halve the time,
but in practice it's erratic, and often counter-productive.

The only change I've so far found to make a consistent improvement, is
to short-circuit the way we go back and forth, gang lookup packing
entries into the array supplied, then shmem scanning that array for the
target entry.  Scanning in place doubles the speed, so it's now only
twice as slow as before (or three times slower when the PROVEs are on).

So, add radix_tree_locate_item() as an expedient, once-off,
single-caller hack to do the lookup directly in place.  #ifdef it on
CONFIG_SHMEM and CONFIG_SWAP, as much to document its limited
applicability as save space in other configurations.  And, sadly,
#include sched.h for cond_resched().

Signed-off-by: Hugh Dickins &lt;hughd@google.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
We have already acknowledged that swapoff of a tmpfs file is slower than
it was before conversion to the generic radix_tree: a little slower
there will be acceptable, if the hotter paths are faster.

But it was a shock to find swapoff of a 500MB file 20 times slower on my
laptop, taking 10 minutes; and at that rate it significantly slows down
my testing.

Now, most of that turned out to be overhead from PROVE_LOCKING and
PROVE_RCU: without those it was only 4 times slower than before; and
more realistic tests on other machines don't fare as badly.

I've tried a number of things to improve it, including tagging the swap
entries, then doing lookup by tag: I'd expected that to halve the time,
but in practice it's erratic, and often counter-productive.

The only change I've so far found to make a consistent improvement, is
to short-circuit the way we go back and forth, gang lookup packing
entries into the array supplied, then shmem scanning that array for the
target entry.  Scanning in place doubles the speed, so it's now only
twice as slow as before (or three times slower when the PROVEs are on).

So, add radix_tree_locate_item() as an expedient, once-off,
single-caller hack to do the lookup directly in place.  #ifdef it on
CONFIG_SHMEM and CONFIG_SWAP, as much to document its limited
applicability as save space in other configurations.  And, sadly,
#include sched.h for cond_resched().

Signed-off-by: Hugh Dickins &lt;hughd@google.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>radix_tree: exceptional entries and indices</title>
<updated>2011-08-04T00:25:22+00:00</updated>
<author>
<name>Hugh Dickins</name>
<email>hughd@google.com</email>
</author>
<published>2011-08-03T23:21:18+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=6328650bb4d854a7dc1498d1c0048b838b0d340c'/>
<id>6328650bb4d854a7dc1498d1c0048b838b0d340c</id>
<content type='text'>
A patchset to extend tmpfs to MAX_LFS_FILESIZE by abandoning its
peculiar swap vector, instead keeping a file's swap entries in the same
radix tree as its struct page pointers: thus saving memory, and
simplifying its code and locking.

This patch:

The radix_tree is used by several subsystems for different purposes.  A
major use is to store the struct page pointers of a file's pagecache for
memory management.  But what if mm wanted to store something other than
page pointers there too?

The low bit of a radix_tree entry is already used to denote an indirect
pointer, for internal use, and the unlikely radix_tree_deref_retry()
case.

Define the next bit as denoting an exceptional entry, and supply inline
functions radix_tree_exception() to return non-0 in either unlikely
case, and radix_tree_exceptional_entry() to return non-0 in the second
case.

If a subsystem already uses radix_tree with that bit set, no problem: it
does not affect internal workings at all, but is defined for the
convenience of those storing well-aligned pointers in the radix_tree.

The radix_tree_gang_lookups have an implicit assumption that the caller
can deduce the offset of each entry returned e.g.  by the page-&gt;index of
a struct page.  But that may not be feasible for some kinds of item to
be stored there.

radix_tree_gang_lookup_slot() allow for an optional indices argument,
output array in which to return those offsets.  The same could be added
to other radix_tree_gang_lookups, but for now keep it to the only one
for which we need it.

Signed-off-by: Hugh Dickins &lt;hughd@google.com&gt;
Acked-by: Rik van Riel &lt;riel@redhat.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
A patchset to extend tmpfs to MAX_LFS_FILESIZE by abandoning its
peculiar swap vector, instead keeping a file's swap entries in the same
radix tree as its struct page pointers: thus saving memory, and
simplifying its code and locking.

This patch:

The radix_tree is used by several subsystems for different purposes.  A
major use is to store the struct page pointers of a file's pagecache for
memory management.  But what if mm wanted to store something other than
page pointers there too?

The low bit of a radix_tree entry is already used to denote an indirect
pointer, for internal use, and the unlikely radix_tree_deref_retry()
case.

Define the next bit as denoting an exceptional entry, and supply inline
functions radix_tree_exception() to return non-0 in either unlikely
case, and radix_tree_exceptional_entry() to return non-0 in the second
case.

If a subsystem already uses radix_tree with that bit set, no problem: it
does not affect internal workings at all, but is defined for the
convenience of those storing well-aligned pointers in the radix_tree.

The radix_tree_gang_lookups have an implicit assumption that the caller
can deduce the offset of each entry returned e.g.  by the page-&gt;index of
a struct page.  But that may not be feasible for some kinds of item to
be stored there.

radix_tree_gang_lookup_slot() allow for an optional indices argument,
output array in which to return those offsets.  The same could be added
to other radix_tree_gang_lookups, but for now keep it to the only one
for which we need it.

Signed-off-by: Hugh Dickins &lt;hughd@google.com&gt;
Acked-by: Rik van Riel &lt;riel@redhat.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ida: simplified functions for id allocation</title>
<updated>2011-08-04T00:25:20+00:00</updated>
<author>
<name>Rusty Russell</name>
<email>rusty@rustcorp.com.au</email>
</author>
<published>2011-08-03T23:21:06+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=88eca0207cf1574328c3ce8c3be537a9317261bb'/>
<id>88eca0207cf1574328c3ce8c3be537a9317261bb</id>
<content type='text'>
The current hyper-optimized functions are overkill if you simply want to
allocate an id for a device.  Create versions which use an internal
lock.

In followup patches, numerous drivers are converted to use this
interface.

Thanks to Tejun for feedback.

Signed-off-by: Rusty Russell &lt;rusty@rustcorp.com.au&gt;
Acked-by: Tejun Heo &lt;tj@kernel.org&gt;
Acked-by: Jonathan Cameron &lt;jic23@cam.ac.uk&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The current hyper-optimized functions are overkill if you simply want to
allocate an id for a device.  Create versions which use an internal
lock.

In followup patches, numerous drivers are converted to use this
interface.

Thanks to Tejun for feedback.

Signed-off-by: Rusty Russell &lt;rusty@rustcorp.com.au&gt;
Acked-by: Tejun Heo &lt;tj@kernel.org&gt;
Acked-by: Jonathan Cameron &lt;jic23@cam.ac.uk&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>fault-injection: add ability to export fault_attr in arbitrary directory</title>
<updated>2011-08-04T00:25:20+00:00</updated>
<author>
<name>Akinobu Mita</name>
<email>akinobu.mita@gmail.com</email>
</author>
<published>2011-08-03T23:21:01+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=dd48c085c1cdf9446f92826f1fd451167fb6c2fd'/>
<id>dd48c085c1cdf9446f92826f1fd451167fb6c2fd</id>
<content type='text'>
init_fault_attr_dentries() is used to export fault_attr via debugfs.
But it can only export it in debugfs root directory.

Per Forlin is working on mmc_fail_request which adds support to inject
data errors after a completed host transfer in MMC subsystem.

The fault_attr for mmc_fail_request should be defined per mmc host and
export it in debugfs directory per mmc host like
/sys/kernel/debug/mmc0/mmc_fail_request.

init_fault_attr_dentries() doesn't help for mmc_fail_request.  So this
introduces fault_create_debugfs_attr() which is able to create a
directory in the arbitrary directory and replace
init_fault_attr_dentries().

[akpm@linux-foundation.org: extraneous semicolon, per Randy]
Signed-off-by: Akinobu Mita &lt;akinobu.mita@gmail.com&gt;
Tested-by: Per Forlin &lt;per.forlin@linaro.org&gt;
Cc: Jens Axboe &lt;axboe@kernel.dk&gt;
Cc: Christoph Lameter &lt;cl@linux-foundation.org&gt;
Cc: Pekka Enberg &lt;penberg@kernel.org&gt;
Cc: Matt Mackall &lt;mpm@selenic.com&gt;
Cc: Randy Dunlap &lt;rdunlap@xenotime.net&gt;
Cc: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
init_fault_attr_dentries() is used to export fault_attr via debugfs.
But it can only export it in debugfs root directory.

Per Forlin is working on mmc_fail_request which adds support to inject
data errors after a completed host transfer in MMC subsystem.

The fault_attr for mmc_fail_request should be defined per mmc host and
export it in debugfs directory per mmc host like
/sys/kernel/debug/mmc0/mmc_fail_request.

init_fault_attr_dentries() doesn't help for mmc_fail_request.  So this
introduces fault_create_debugfs_attr() which is able to create a
directory in the arbitrary directory and replace
init_fault_attr_dentries().

[akpm@linux-foundation.org: extraneous semicolon, per Randy]
Signed-off-by: Akinobu Mita &lt;akinobu.mita@gmail.com&gt;
Tested-by: Per Forlin &lt;per.forlin@linaro.org&gt;
Cc: Jens Axboe &lt;axboe@kernel.dk&gt;
Cc: Christoph Lameter &lt;cl@linux-foundation.org&gt;
Cc: Pekka Enberg &lt;penberg@kernel.org&gt;
Cc: Matt Mackall &lt;mpm@selenic.com&gt;
Cc: Randy Dunlap &lt;rdunlap@xenotime.net&gt;
Cc: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'apei' into apei-release</title>
<updated>2011-08-03T15:30:42+00:00</updated>
<author>
<name>Len Brown</name>
<email>len.brown@intel.com</email>
</author>
<published>2011-08-03T15:30:42+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=d0e323b47057f4492b8fa22345f38d80a469bf8d'/>
<id>d0e323b47057f4492b8fa22345f38d80a469bf8d</id>
<content type='text'>
Some trivial conflicts due to other various merges
adding to the end of common lists sooner than this one.

	arch/ia64/Kconfig
	arch/powerpc/Kconfig
	arch/x86/Kconfig
	lib/Kconfig
	lib/Makefile

Signed-off-by: Len Brown &lt;len.brown@intel.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Some trivial conflicts due to other various merges
adding to the end of common lists sooner than this one.

	arch/ia64/Kconfig
	arch/powerpc/Kconfig
	arch/x86/Kconfig
	lib/Kconfig
	lib/Makefile

Signed-off-by: Len Brown &lt;len.brown@intel.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>lib, Make gen_pool memory allocator lockless</title>
<updated>2011-08-03T15:15:57+00:00</updated>
<author>
<name>Huang Ying</name>
<email>ying.huang@intel.com</email>
</author>
<published>2011-07-13T05:14:24+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=7f184275aa306046fe7edcbef3229754f0d97402'/>
<id>7f184275aa306046fe7edcbef3229754f0d97402</id>
<content type='text'>
This version of the gen_pool memory allocator supports lockless
operation.

This makes it safe to use in NMI handlers and other special
unblockable contexts that could otherwise deadlock on locks.  This is
implemented by using atomic operations and retries on any conflicts.
The disadvantage is that there may be livelocks in extreme cases.  For
better scalability, one gen_pool allocator can be used for each CPU.

The lockless operation only works if there is enough memory available.
If new memory is added to the pool a lock has to be still taken.  So
any user relying on locklessness has to ensure that sufficient memory
is preallocated.

The basic atomic operation of this allocator is cmpxchg on long.  On
architectures that don't have NMI-safe cmpxchg implementation, the
allocator can NOT be used in NMI handler.  So code uses the allocator
in NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.

Signed-off-by: Huang Ying &lt;ying.huang@intel.com&gt;
Reviewed-by: Andi Kleen &lt;ak@linux.intel.com&gt;
Reviewed-by: Mathieu Desnoyers &lt;mathieu.desnoyers@efficios.com&gt;
Cc: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Len Brown &lt;len.brown@intel.com&gt;
</content>
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<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This version of the gen_pool memory allocator supports lockless
operation.

This makes it safe to use in NMI handlers and other special
unblockable contexts that could otherwise deadlock on locks.  This is
implemented by using atomic operations and retries on any conflicts.
The disadvantage is that there may be livelocks in extreme cases.  For
better scalability, one gen_pool allocator can be used for each CPU.

The lockless operation only works if there is enough memory available.
If new memory is added to the pool a lock has to be still taken.  So
any user relying on locklessness has to ensure that sufficient memory
is preallocated.

The basic atomic operation of this allocator is cmpxchg on long.  On
architectures that don't have NMI-safe cmpxchg implementation, the
allocator can NOT be used in NMI handler.  So code uses the allocator
in NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.

Signed-off-by: Huang Ying &lt;ying.huang@intel.com&gt;
Reviewed-by: Andi Kleen &lt;ak@linux.intel.com&gt;
Reviewed-by: Mathieu Desnoyers &lt;mathieu.desnoyers@efficios.com&gt;
Cc: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Len Brown &lt;len.brown@intel.com&gt;
</pre>
</div>
</content>
</entry>
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