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Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/gi…
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…t/torvalds/linux into sh-fixes-for-linus
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Paul Mundt committed Aug 26, 2011
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2 changes: 2 additions & 0 deletions Documentation/00-INDEX
Original file line number Diff line number Diff line change
Expand Up @@ -272,6 +272,8 @@ printk-formats.txt
- how to get printk format specifiers right
prio_tree.txt
- info on radix-priority-search-tree use for indexing vmas.
ramoops.txt
- documentation of the ramoops oops/panic logging module.
rbtree.txt
- info on what red-black trees are and what they are for.
robust-futex-ABI.txt
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89 changes: 44 additions & 45 deletions Documentation/PCI/MSI-HOWTO.txt
Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,7 @@ arrived in memory (this becomes more likely with devices behind PCI-PCI
bridges). In order to ensure that all the data has arrived in memory,
the interrupt handler must read a register on the device which raised
the interrupt. PCI transaction ordering rules require that all the data
arrives in memory before the value can be returned from the register.
arrive in memory before the value may be returned from the register.
Using MSIs avoids this problem as the interrupt-generating write cannot
pass the data writes, so by the time the interrupt is raised, the driver
knows that all the data has arrived in memory.
Expand Down Expand Up @@ -86,13 +86,13 @@ device.

int pci_enable_msi(struct pci_dev *dev)

A successful call will allocate ONE interrupt to the device, regardless
of how many MSIs the device supports. The device will be switched from
A successful call allocates ONE interrupt to the device, regardless
of how many MSIs the device supports. The device is switched from
pin-based interrupt mode to MSI mode. The dev->irq number is changed
to a new number which represents the message signaled interrupt.
This function should be called before the driver calls request_irq()
since enabling MSIs disables the pin-based IRQ and the driver will not
receive interrupts on the old interrupt.
to a new number which represents the message signaled interrupt;
consequently, this function should be called before the driver calls
request_irq(), because an MSI is delivered via a vector that is
different from the vector of a pin-based interrupt.

4.2.2 pci_enable_msi_block

Expand All @@ -111,20 +111,20 @@ the device are in the range dev->irq to dev->irq + count - 1.

If this function returns a negative number, it indicates an error and
the driver should not attempt to request any more MSI interrupts for
this device. If this function returns a positive number, it will be
less than 'count' and indicate the number of interrupts that could have
been allocated. In neither case will the irq value have been
updated, nor will the device have been switched into MSI mode.
this device. If this function returns a positive number, it is
less than 'count' and indicates the number of interrupts that could have
been allocated. In neither case is the irq value updated or the device
switched into MSI mode.

The device driver must decide what action to take if
pci_enable_msi_block() returns a value less than the number asked for.
Some devices can make use of fewer interrupts than the maximum they
request; in this case the driver should call pci_enable_msi_block()
pci_enable_msi_block() returns a value less than the number requested.
For instance, the driver could still make use of fewer interrupts;
in this case the driver should call pci_enable_msi_block()
again. Note that it is not guaranteed to succeed, even when the
'count' has been reduced to the value returned from a previous call to
pci_enable_msi_block(). This is because there are multiple constraints
on the number of vectors that can be allocated; pci_enable_msi_block()
will return as soon as it finds any constraint that doesn't allow the
returns as soon as it finds any constraint that doesn't allow the
call to succeed.

4.2.3 pci_disable_msi
Expand All @@ -137,10 +137,10 @@ interrupt number and frees the previously allocated message signaled
interrupt(s). The interrupt may subsequently be assigned to another
device, so drivers should not cache the value of dev->irq.

A device driver must always call free_irq() on the interrupt(s)
for which it has called request_irq() before calling this function.
Failure to do so will result in a BUG_ON(), the device will be left with
MSI enabled and will leak its vector.
Before calling this function, a device driver must always call free_irq()
on any interrupt for which it previously called request_irq().
Failure to do so results in a BUG_ON(), leaving the device with
MSI enabled and thus leaking its vector.

4.3 Using MSI-X

Expand All @@ -155,10 +155,10 @@ struct msix_entry {
};

This allows for the device to use these interrupts in a sparse fashion;
for example it could use interrupts 3 and 1027 and allocate only a
for example, it could use interrupts 3 and 1027 and yet allocate only a
two-element array. The driver is expected to fill in the 'entry' value
in each element of the array to indicate which entries it wants the kernel
to assign interrupts for. It is invalid to fill in two entries with the
in each element of the array to indicate for which entries the kernel
should assign interrupts; it is invalid to fill in two entries with the
same number.

4.3.1 pci_enable_msix
Expand All @@ -168,10 +168,11 @@ int pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries, int nvec)
Calling this function asks the PCI subsystem to allocate 'nvec' MSIs.
The 'entries' argument is a pointer to an array of msix_entry structs
which should be at least 'nvec' entries in size. On success, the
function will return 0 and the device will have been switched into
MSI-X interrupt mode. The 'vector' elements in each entry will have
been filled in with the interrupt number. The driver should then call
request_irq() for each 'vector' that it decides to use.
device is switched into MSI-X mode and the function returns 0.
The 'vector' member in each entry is populated with the interrupt number;
the driver should then call request_irq() for each 'vector' that it
decides to use. The device driver is responsible for keeping track of the
interrupts assigned to the MSI-X vectors so it can free them again later.

If this function returns a negative number, it indicates an error and
the driver should not attempt to allocate any more MSI-X interrupts for
Expand All @@ -181,16 +182,14 @@ below.

This function, in contrast with pci_enable_msi(), does not adjust
dev->irq. The device will not generate interrupts for this interrupt
number once MSI-X is enabled. The device driver is responsible for
keeping track of the interrupts assigned to the MSI-X vectors so it can
free them again later.
number once MSI-X is enabled.

Device drivers should normally call this function once per device
during the initialization phase.

It is ideal if drivers can cope with a variable number of MSI-X interrupts,
It is ideal if drivers can cope with a variable number of MSI-X interrupts;
there are many reasons why the platform may not be able to provide the
exact number a driver asks for.
exact number that a driver asks for.

A request loop to achieve that might look like:

Expand All @@ -212,15 +211,15 @@ static int foo_driver_enable_msix(struct foo_adapter *adapter, int nvec)

void pci_disable_msix(struct pci_dev *dev)

This API should be used to undo the effect of pci_enable_msix(). It frees
This function should be used to undo the effect of pci_enable_msix(). It frees
the previously allocated message signaled interrupts. The interrupts may
subsequently be assigned to another device, so drivers should not cache
the value of the 'vector' elements over a call to pci_disable_msix().

A device driver must always call free_irq() on the interrupt(s)
for which it has called request_irq() before calling this function.
Failure to do so will result in a BUG_ON(), the device will be left with
MSI enabled and will leak its vector.
Before calling this function, a device driver must always call free_irq()
on any interrupt for which it previously called request_irq().
Failure to do so results in a BUG_ON(), leaving the device with
MSI-X enabled and thus leaking its vector.

4.3.3 The MSI-X Table

Expand All @@ -232,10 +231,10 @@ mask or unmask an interrupt, it should call disable_irq() / enable_irq().
4.4 Handling devices implementing both MSI and MSI-X capabilities

If a device implements both MSI and MSI-X capabilities, it can
run in either MSI mode or MSI-X mode but not both simultaneously.
run in either MSI mode or MSI-X mode, but not both simultaneously.
This is a requirement of the PCI spec, and it is enforced by the
PCI layer. Calling pci_enable_msi() when MSI-X is already enabled or
pci_enable_msix() when MSI is already enabled will result in an error.
pci_enable_msix() when MSI is already enabled results in an error.
If a device driver wishes to switch between MSI and MSI-X at runtime,
it must first quiesce the device, then switch it back to pin-interrupt
mode, before calling pci_enable_msi() or pci_enable_msix() and resuming
Expand All @@ -251,7 +250,7 @@ the MSI-X facilities in preference to the MSI facilities. As mentioned
above, MSI-X supports any number of interrupts between 1 and 2048.
In constrast, MSI is restricted to a maximum of 32 interrupts (and
must be a power of two). In addition, the MSI interrupt vectors must
be allocated consecutively, so the system may not be able to allocate
be allocated consecutively, so the system might not be able to allocate
as many vectors for MSI as it could for MSI-X. On some platforms, MSI
interrupts must all be targeted at the same set of CPUs whereas MSI-X
interrupts can all be targeted at different CPUs.
Expand Down Expand Up @@ -281,7 +280,7 @@ disabled to enabled and back again.

Using 'lspci -v' (as root) may show some devices with "MSI", "Message
Signalled Interrupts" or "MSI-X" capabilities. Each of these capabilities
has an 'Enable' flag which will be followed with either "+" (enabled)
has an 'Enable' flag which is followed with either "+" (enabled)
or "-" (disabled).


Expand All @@ -298,7 +297,7 @@ The PCI stack provides three ways to disable MSIs:

Some host chipsets simply don't support MSIs properly. If we're
lucky, the manufacturer knows this and has indicated it in the ACPI
FADT table. In this case, Linux will automatically disable MSIs.
FADT table. In this case, Linux automatically disables MSIs.
Some boards don't include this information in the table and so we have
to detect them ourselves. The complete list of these is found near the
quirk_disable_all_msi() function in drivers/pci/quirks.c.
Expand All @@ -317,7 +316,7 @@ Some bridges allow you to enable MSIs by changing some bits in their
PCI configuration space (especially the Hypertransport chipsets such
as the nVidia nForce and Serverworks HT2000). As with host chipsets,
Linux mostly knows about them and automatically enables MSIs if it can.
If you have a bridge which Linux doesn't yet know about, you can enable
If you have a bridge unknown to Linux, you can enable
MSIs in configuration space using whatever method you know works, then
enable MSIs on that bridge by doing:

Expand All @@ -327,7 +326,7 @@ where $bridge is the PCI address of the bridge you've enabled (eg
0000:00:0e.0).

To disable MSIs, echo 0 instead of 1. Changing this value should be
done with caution as it can break interrupt handling for all devices
done with caution as it could break interrupt handling for all devices
below this bridge.

Again, please notify linux-pci@vger.kernel.org of any bridges that need
Expand All @@ -336,7 +335,7 @@ special handling.
5.3. Disabling MSIs on a single device

Some devices are known to have faulty MSI implementations. Usually this
is handled in the individual device driver but occasionally it's necessary
is handled in the individual device driver, but occasionally it's necessary
to handle this with a quirk. Some drivers have an option to disable use
of MSI. While this is a convenient workaround for the driver author,
it is not good practise, and should not be emulated.
Expand All @@ -350,7 +349,7 @@ for your machine. You should also check your .config to be sure you
have enabled CONFIG_PCI_MSI.

Then, 'lspci -t' gives the list of bridges above a device. Reading
/sys/bus/pci/devices/*/msi_bus will tell you whether MSI are enabled (1)
/sys/bus/pci/devices/*/msi_bus will tell you whether MSIs are enabled (1)
or disabled (0). If 0 is found in any of the msi_bus files belonging
to bridges between the PCI root and the device, MSIs are disabled.

Expand Down
2 changes: 1 addition & 1 deletion Documentation/SubmittingDrivers
Original file line number Diff line number Diff line change
Expand Up @@ -130,7 +130,7 @@ Linux kernel master tree:
ftp.??.kernel.org:/pub/linux/kernel/...
?? == your country code, such as "us", "uk", "fr", etc.

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git

Linux kernel mailing list:
linux-kernel@vger.kernel.org
Expand Down
2 changes: 1 addition & 1 deletion Documentation/SubmittingPatches
Original file line number Diff line number Diff line change
Expand Up @@ -303,7 +303,7 @@ patches that are being emailed around.

The sign-off is a simple line at the end of the explanation for the
patch, which certifies that you wrote it or otherwise have the right to
pass it on as a open-source patch. The rules are pretty simple: if you
pass it on as an open-source patch. The rules are pretty simple: if you
can certify the below:

Developer's Certificate of Origin 1.1
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71 changes: 71 additions & 0 deletions Documentation/block/cfq-iosched.txt
Original file line number Diff line number Diff line change
Expand Up @@ -43,3 +43,74 @@ If one sets slice_idle=0 and if storage supports NCQ, CFQ internally switches
to IOPS mode and starts providing fairness in terms of number of requests
dispatched. Note that this mode switching takes effect only for group
scheduling. For non-cgroup users nothing should change.

CFQ IO scheduler Idling Theory
===============================
Idling on a queue is primarily about waiting for the next request to come
on same queue after completion of a request. In this process CFQ will not
dispatch requests from other cfq queues even if requests are pending there.

The rationale behind idling is that it can cut down on number of seeks
on rotational media. For example, if a process is doing dependent
sequential reads (next read will come on only after completion of previous
one), then not dispatching request from other queue should help as we
did not move the disk head and kept on dispatching sequential IO from
one queue.

CFQ has following service trees and various queues are put on these trees.

sync-idle sync-noidle async

All cfq queues doing synchronous sequential IO go on to sync-idle tree.
On this tree we idle on each queue individually.

All synchronous non-sequential queues go on sync-noidle tree. Also any
request which are marked with REQ_NOIDLE go on this service tree. On this
tree we do not idle on individual queues instead idle on the whole group
of queues or the tree. So if there are 4 queues waiting for IO to dispatch
we will idle only once last queue has dispatched the IO and there is
no more IO on this service tree.

All async writes go on async service tree. There is no idling on async
queues.

CFQ has some optimizations for SSDs and if it detects a non-rotational
media which can support higher queue depth (multiple requests at in
flight at a time), then it cuts down on idling of individual queues and
all the queues move to sync-noidle tree and only tree idle remains. This
tree idling provides isolation with buffered write queues on async tree.

FAQ
===
Q1. Why to idle at all on queues marked with REQ_NOIDLE.

A1. We only do tree idle (all queues on sync-noidle tree) on queues marked
with REQ_NOIDLE. This helps in providing isolation with all the sync-idle
queues. Otherwise in presence of many sequential readers, other
synchronous IO might not get fair share of disk.

For example, if there are 10 sequential readers doing IO and they get
100ms each. If a REQ_NOIDLE request comes in, it will be scheduled
roughly after 1 second. If after completion of REQ_NOIDLE request we
do not idle, and after a couple of milli seconds a another REQ_NOIDLE
request comes in, again it will be scheduled after 1second. Repeat it
and notice how a workload can lose its disk share and suffer due to
multiple sequential readers.

fsync can generate dependent IO where bunch of data is written in the
context of fsync, and later some journaling data is written. Journaling
data comes in only after fsync has finished its IO (atleast for ext4
that seemed to be the case). Now if one decides not to idle on fsync
thread due to REQ_NOIDLE, then next journaling write will not get
scheduled for another second. A process doing small fsync, will suffer
badly in presence of multiple sequential readers.

Hence doing tree idling on threads using REQ_NOIDLE flag on requests
provides isolation from multiple sequential readers and at the same
time we do not idle on individual threads.

Q2. When to specify REQ_NOIDLE
A2. I would think whenever one is doing synchronous write and not expecting
more writes to be dispatched from same context soon, should be able
to specify REQ_NOIDLE on writes and that probably should work well for
most of the cases.
12 changes: 5 additions & 7 deletions Documentation/email-clients.txt
Original file line number Diff line number Diff line change
Expand Up @@ -199,18 +199,16 @@ to coerce it into behaving.

To beat some sense out of the internal editor, do this:

- Under account settings, composition and addressing, uncheck "Compose
messages in HTML format".

- Edit your Thunderbird config settings so that it won't use format=flowed.
Go to "edit->preferences->advanced->config editor" to bring up the
thunderbird's registry editor, and set "mailnews.send_plaintext_flowed" to
"false".

- Enable "preformat" mode: Shft-click on the Write icon to bring up the HTML
composer, select "Preformat" from the drop-down box just under the subject
line, then close the message without saving. (This setting also applies to
the text composer, but the only control for it is in the HTML composer.)
- Disable HTML Format: Set "mail.identity.id1.compose_html" to "false".

- Enable "preformat" mode: Set "editor.quotesPreformatted" to "true".

- Enable UTF8: Set "prefs.converted-to-utf8" to "true".

- Install the "toggle wordwrap" extension. Download the file from:
https://addons.mozilla.org/thunderbird/addon/2351/
Expand Down
2 changes: 1 addition & 1 deletion Documentation/filesystems/befs.txt
Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,7 @@ His original code can still be found at:
Does anyone know of a more current email address for Makoto? He doesn't
respond to the address given above...

Current maintainer: Sergey S. Kostyliov <rathamahata@php4.ru>
This filesystem doesn't have a maintainer.

WHAT IS THIS DRIVER?
==================
Expand Down
11 changes: 0 additions & 11 deletions Documentation/kernel-docs.txt
Original file line number Diff line number Diff line change
Expand Up @@ -620,17 +620,6 @@
(including this document itself) have been moved there, and might
be more up to date than the web version.

* Name: "Linux Source Driver"
URL: http://lsd.linux.cz
Keywords: Browsing source code.
Description: "Linux Source Driver (LSD) is an application, which
can make browsing source codes of Linux kernel easier than you can
imagine. You can select between multiple versions of kernel (e.g.
0.01, 1.0.0, 2.0.33, 2.0.34pre13, 2.0.0, 2.1.101 etc.). With LSD
you can search Linux kernel (fulltext, macros, types, functions
and variables) and LSD can generate patches for you on the fly
(files, directories or kernel)".

* Name: "Linux Kernel Source Reference"
Author: Thomas Graichen.
URL: http://marc.info/?l=linux-kernel&m=96446640102205&w=4
Expand Down
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