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r: 255260
b: refs/heads/master
c: 997271c
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Linus Torvalds committed Jul 22, 2011
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2 changes: 1 addition & 1 deletion [refs]
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@@ -1,2 +1,2 @@
---
refs/heads/master: 97ffab1f14638d2c95ad986ce735481d164a0bd2
refs/heads/master: 997271cf5e12c1b38aec0764187094663501c984
43 changes: 18 additions & 25 deletions trunk/Documentation/Changes
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Expand Up @@ -2,13 +2,7 @@ Intro
=====

This document is designed to provide a list of the minimum levels of
software necessary to run the 2.6 kernels, as well as provide brief
instructions regarding any other "Gotchas" users may encounter when
trying life on the Bleeding Edge. If upgrading from a pre-2.4.x
kernel, please consult the Changes file included with 2.4.x kernels for
additional information; most of that information will not be repeated
here. Basically, this document assumes that your system is already
functional and running at least 2.4.x kernels.
software necessary to run the 3.0 kernels.

This document is originally based on my "Changes" file for 2.0.x kernels
and therefore owes credit to the same people as that file (Jared Mauch,
Expand All @@ -22,11 +16,10 @@ Upgrade to at *least* these software revisions before thinking you've
encountered a bug! If you're unsure what version you're currently
running, the suggested command should tell you.

Again, keep in mind that this list assumes you are already
functionally running a Linux 2.4 kernel. Also, not all tools are
necessary on all systems; obviously, if you don't have any ISDN
hardware, for example, you probably needn't concern yourself with
isdn4k-utils.
Again, keep in mind that this list assumes you are already functionally
running a Linux kernel. Also, not all tools are necessary on all
systems; obviously, if you don't have any ISDN hardware, for example,
you probably needn't concern yourself with isdn4k-utils.

o Gnu C 3.2 # gcc --version
o Gnu make 3.80 # make --version
Expand Down Expand Up @@ -114,12 +107,12 @@ Ksymoops

If the unthinkable happens and your kernel oopses, you may need the
ksymoops tool to decode it, but in most cases you don't.
In the 2.6 kernel it is generally preferred to build the kernel with
CONFIG_KALLSYMS so that it produces readable dumps that can be used as-is
(this also produces better output than ksymoops).
If for some reason your kernel is not build with CONFIG_KALLSYMS and
you have no way to rebuild and reproduce the Oops with that option, then
you can still decode that Oops with ksymoops.
It is generally preferred to build the kernel with CONFIG_KALLSYMS so
that it produces readable dumps that can be used as-is (this also
produces better output than ksymoops). If for some reason your kernel
is not build with CONFIG_KALLSYMS and you have no way to rebuild and
reproduce the Oops with that option, then you can still decode that Oops
with ksymoops.

Module-Init-Tools
-----------------
Expand Down Expand Up @@ -261,8 +254,8 @@ needs to be recompiled or (preferably) upgraded.
NFS-utils
---------

In 2.4 and earlier kernels, the nfs server needed to know about any
client that expected to be able to access files via NFS. This
In ancient (2.4 and earlier) kernels, the nfs server needed to know
about any client that expected to be able to access files via NFS. This
information would be given to the kernel by "mountd" when the client
mounted the filesystem, or by "exportfs" at system startup. exportfs
would take information about active clients from /var/lib/nfs/rmtab.
Expand All @@ -272,11 +265,11 @@ which is not always easy, particularly when trying to implement
fail-over. Even when the system is working well, rmtab suffers from
getting lots of old entries that never get removed.

With 2.6 we have the option of having the kernel tell mountd when it
gets a request from an unknown host, and mountd can give appropriate
export information to the kernel. This removes the dependency on
rmtab and means that the kernel only needs to know about currently
active clients.
With modern kernels we have the option of having the kernel tell mountd
when it gets a request from an unknown host, and mountd can give
appropriate export information to the kernel. This removes the
dependency on rmtab and means that the kernel only needs to know about
currently active clients.

To enable this new functionality, you need to:

Expand Down
22 changes: 22 additions & 0 deletions trunk/Documentation/feature-removal-schedule.txt
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Expand Up @@ -583,3 +583,25 @@ Why: Superseded by the UVCIOC_CTRL_QUERY ioctl.
Who: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

----------------------------

What: For VIDIOC_S_FREQUENCY the type field must match the device node's type.
If not, return -EINVAL.
When: 3.2
Why: It makes no sense to switch the tuner to radio mode by calling
VIDIOC_S_FREQUENCY on a video node, or to switch the tuner to tv mode by
calling VIDIOC_S_FREQUENCY on a radio node. This is the first step of a
move to more consistent handling of tv and radio tuners.
Who: Hans Verkuil <hans.verkuil@cisco.com>

----------------------------

What: Opening a radio device node will no longer automatically switch the
tuner mode from tv to radio.
When: 3.3
Why: Just opening a V4L device should not change the state of the hardware
like that. It's very unexpected and against the V4L spec. Instead, you
switch to radio mode by calling VIDIOC_S_FREQUENCY. This is the second
and last step of the move to consistent handling of tv and radio tuners.
Who: Hans Verkuil <hans.verkuil@cisco.com>

----------------------------
16 changes: 16 additions & 0 deletions trunk/Documentation/filesystems/caching/netfs-api.txt
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Expand Up @@ -673,6 +673,22 @@ storage request to complete, or it may attempt to cancel the storage request -
in which case the page will not be stored in the cache this time.


BULK INODE PAGE UNCACHE
-----------------------

A convenience routine is provided to perform an uncache on all the pages
attached to an inode. This assumes that the pages on the inode correspond on a
1:1 basis with the pages in the cache.

void fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
struct inode *inode);

This takes the netfs cookie that the pages were cached with and the inode that
the pages are attached to. This function will wait for pages to finish being
written to the cache and for the cache to finish with the page generally. No
error is returned.


==========================
INDEX AND DATA FILE UPDATE
==========================
Expand Down
1 change: 0 additions & 1 deletion trunk/Documentation/filesystems/nilfs2.txt
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Expand Up @@ -40,7 +40,6 @@ Features which NILFS2 does not support yet:
- POSIX ACLs
- quotas
- fsck
- resize
- defragmentation

Mount options
Expand Down
28 changes: 0 additions & 28 deletions trunk/Documentation/filesystems/ubifs.txt
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Expand Up @@ -111,34 +111,6 @@ The following is an example of the kernel boot arguments to attach mtd0
to UBI and mount volume "rootfs":
ubi.mtd=0 root=ubi0:rootfs rootfstype=ubifs


Module Parameters for Debugging
===============================

When UBIFS has been compiled with debugging enabled, there are 2 module
parameters that are available to control aspects of testing and debugging.

debug_chks Selects extra checks that UBIFS can do while running:

Check Flag value

General checks 1
Check Tree Node Cache (TNC) 2
Check indexing tree size 4
Check orphan area 8
Check old indexing tree 16
Check LEB properties (lprops) 32
Check leaf nodes and inodes 64

debug_tsts Selects a mode of testing, as follows:

Test mode Flag value

Failure mode for recovery testing 4

For example, set debug_chks to 3 to enable general and TNC checks.


References
==========

Expand Down
2 changes: 2 additions & 0 deletions trunk/Documentation/kernel-parameters.txt
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Expand Up @@ -2015,6 +2015,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
the default.
off: Turn ECRC off
on: Turn ECRC on.
realloc reallocate PCI resources if allocations done by BIOS
are erroneous.

pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
Management.
Expand Down
5 changes: 5 additions & 0 deletions trunk/Documentation/laptops/thinkpad-acpi.txt
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Expand Up @@ -534,6 +534,8 @@ Events that are never propagated by the driver:
0x2404 System is waking up from hibernation to undock
0x2405 System is waking up from hibernation to eject bay
0x5010 Brightness level changed/control event
0x6000 KEYBOARD: Numlock key pressed
0x6005 KEYBOARD: Fn key pressed (TO BE VERIFIED)

Events that are propagated by the driver to userspace:

Expand All @@ -545,13 +547,16 @@ Events that are propagated by the driver to userspace:
0x3006 Bay hotplug request (hint to power up SATA link when
the optical drive tray is ejected)
0x4003 Undocked (see 0x2x04), can sleep again
0x4010 Docked into hotplug port replicator (non-ACPI dock)
0x4011 Undocked from hotplug port replicator (non-ACPI dock)
0x500B Tablet pen inserted into its storage bay
0x500C Tablet pen removed from its storage bay
0x6011 ALARM: battery is too hot
0x6012 ALARM: battery is extremely hot
0x6021 ALARM: a sensor is too hot
0x6022 ALARM: a sensor is extremely hot
0x6030 System thermal table changed
0x6040 Nvidia Optimus/AC adapter related (TO BE VERIFIED)

Battery nearly empty alarms are a last resort attempt to get the
operating system to hibernate or shutdown cleanly (0x2313), or shutdown
Expand Down
2 changes: 2 additions & 0 deletions trunk/Documentation/mmc/00-INDEX
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Expand Up @@ -4,3 +4,5 @@ mmc-dev-attrs.txt
- info on SD and MMC device attributes
mmc-dev-parts.txt
- info on SD and MMC device partitions
mmc-async-req.txt
- info on mmc asynchronous requests
87 changes: 87 additions & 0 deletions trunk/Documentation/mmc/mmc-async-req.txt
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@@ -0,0 +1,87 @@
Rationale
=========

How significant is the cache maintenance overhead?
It depends. Fast eMMC and multiple cache levels with speculative cache
pre-fetch makes the cache overhead relatively significant. If the DMA
preparations for the next request are done in parallel with the current
transfer, the DMA preparation overhead would not affect the MMC performance.
The intention of non-blocking (asynchronous) MMC requests is to minimize the
time between when an MMC request ends and another MMC request begins.
Using mmc_wait_for_req(), the MMC controller is idle while dma_map_sg and
dma_unmap_sg are processing. Using non-blocking MMC requests makes it
possible to prepare the caches for next job in parallel with an active
MMC request.

MMC block driver
================

The mmc_blk_issue_rw_rq() in the MMC block driver is made non-blocking.
The increase in throughput is proportional to the time it takes to
prepare (major part of preparations are dma_map_sg() and dma_unmap_sg())
a request and how fast the memory is. The faster the MMC/SD is the
more significant the prepare request time becomes. Roughly the expected
performance gain is 5% for large writes and 10% on large reads on a L2 cache
platform. In power save mode, when clocks run on a lower frequency, the DMA
preparation may cost even more. As long as these slower preparations are run
in parallel with the transfer performance won't be affected.

Details on measurements from IOZone and mmc_test
================================================

https://wiki.linaro.org/WorkingGroups/Kernel/Specs/StoragePerfMMC-async-req

MMC core API extension
======================

There is one new public function mmc_start_req().
It starts a new MMC command request for a host. The function isn't
truly non-blocking. If there is an ongoing async request it waits
for completion of that request and starts the new one and returns. It
doesn't wait for the new request to complete. If there is no ongoing
request it starts the new request and returns immediately.

MMC host extensions
===================

There are two optional members in the mmc_host_ops -- pre_req() and
post_req() -- that the host driver may implement in order to move work
to before and after the actual mmc_host_ops.request() function is called.
In the DMA case pre_req() may do dma_map_sg() and prepare the DMA
descriptor, and post_req() runs the dma_unmap_sg().

Optimize for the first request
==============================

The first request in a series of requests can't be prepared in parallel
with the previous transfer, since there is no previous request.
The argument is_first_req in pre_req() indicates that there is no previous
request. The host driver may optimize for this scenario to minimize
the performance loss. A way to optimize for this is to split the current
request in two chunks, prepare the first chunk and start the request,
and finally prepare the second chunk and start the transfer.

Pseudocode to handle is_first_req scenario with minimal prepare overhead:

if (is_first_req && req->size > threshold)
/* start MMC transfer for the complete transfer size */
mmc_start_command(MMC_CMD_TRANSFER_FULL_SIZE);

/*
* Begin to prepare DMA while cmd is being processed by MMC.
* The first chunk of the request should take the same time
* to prepare as the "MMC process command time".
* If prepare time exceeds MMC cmd time
* the transfer is delayed, guesstimate max 4k as first chunk size.
*/
prepare_1st_chunk_for_dma(req);
/* flush pending desc to the DMAC (dmaengine.h) */
dma_issue_pending(req->dma_desc);

prepare_2nd_chunk_for_dma(req);
/*
* The second issue_pending should be called before MMC runs out
* of the first chunk. If the MMC runs out of the first data chunk
* before this call, the transfer is delayed.
*/
dma_issue_pending(req->dma_desc);
2 changes: 1 addition & 1 deletion trunk/Documentation/networking/ip-sysctl.txt
Original file line number Diff line number Diff line change
Expand Up @@ -346,7 +346,7 @@ tcp_orphan_retries - INTEGER
when RTO retransmissions remain unacknowledged.
See tcp_retries2 for more details.

The default value is 7.
The default value is 8.
If your machine is a loaded WEB server,
you should think about lowering this value, such sockets
may consume significant resources. Cf. tcp_max_orphans.
Expand Down
45 changes: 7 additions & 38 deletions trunk/Documentation/spinlocks.txt
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Expand Up @@ -13,18 +13,8 @@ static DEFINE_SPINLOCK(xxx_lock);
The above is always safe. It will disable interrupts _locally_, but the
spinlock itself will guarantee the global lock, so it will guarantee that
there is only one thread-of-control within the region(s) protected by that
lock. This works well even under UP. The above sequence under UP
essentially is just the same as doing

unsigned long flags;

save_flags(flags); cli();
... critical section ...
restore_flags(flags);

so the code does _not_ need to worry about UP vs SMP issues: the spinlocks
work correctly under both (and spinlocks are actually more efficient on
architectures that allow doing the "save_flags + cli" in one operation).
lock. This works well even under UP also, so the code does _not_ need to
worry about UP vs SMP issues: the spinlocks work correctly under both.

NOTE! Implications of spin_locks for memory are further described in:

Expand All @@ -36,27 +26,7 @@ The above is usually pretty simple (you usually need and want only one
spinlock for most things - using more than one spinlock can make things a
lot more complex and even slower and is usually worth it only for
sequences that you _know_ need to be split up: avoid it at all cost if you
aren't sure). HOWEVER, it _does_ mean that if you have some code that does

cli();
.. critical section ..
sti();

and another sequence that does

spin_lock_irqsave(flags);
.. critical section ..
spin_unlock_irqrestore(flags);

then they are NOT mutually exclusive, and the critical regions can happen
at the same time on two different CPU's. That's fine per se, but the
critical regions had better be critical for different things (ie they
can't stomp on each other).

The above is a problem mainly if you end up mixing code - for example the
routines in ll_rw_block() tend to use cli/sti to protect the atomicity of
their actions, and if a driver uses spinlocks instead then you should
think about issues like the above.
aren't sure).

This is really the only really hard part about spinlocks: once you start
using spinlocks they tend to expand to areas you might not have noticed
Expand Down Expand Up @@ -120,11 +90,10 @@ Lesson 3: spinlocks revisited.

The single spin-lock primitives above are by no means the only ones. They
are the most safe ones, and the ones that work under all circumstances,
but partly _because_ they are safe they are also fairly slow. They are
much faster than a generic global cli/sti pair, but slower than they'd
need to be, because they do have to disable interrupts (which is just a
single instruction on a x86, but it's an expensive one - and on other
architectures it can be worse).
but partly _because_ they are safe they are also fairly slow. They are slower
than they'd need to be, because they do have to disable interrupts
(which is just a single instruction on a x86, but it's an expensive one -
and on other architectures it can be worse).

If you have a case where you have to protect a data structure across
several CPU's and you want to use spinlocks you can potentially use
Expand Down
2 changes: 1 addition & 1 deletion trunk/Documentation/x86/boot.txt
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Expand Up @@ -674,7 +674,7 @@ Protocol: 2.10+

Field name: init_size
Type: read
Offset/size: 0x25c/4
Offset/size: 0x260/4

This field indicates the amount of linear contiguous memory starting
at the kernel runtime start address that the kernel needs before it
Expand Down
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