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Anton Altaparmakov committed Jan 19, 2006
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2 changes: 2 additions & 0 deletions .gitignore
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Expand Up @@ -10,6 +10,7 @@
*.a
*.s
*.ko
*.so
*.mod.c

#
Expand All @@ -23,6 +24,7 @@ Module.symvers
# Generated include files
#
include/asm
include/asm-*/asm-offsets.h
include/config
include/linux/autoconf.h
include/linux/compile.h
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3 changes: 2 additions & 1 deletion CREDITS
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Expand Up @@ -1883,6 +1883,7 @@ N: Jaya Kumar
E: jayalk@intworks.biz
W: http://www.intworks.biz
D: Arc monochrome LCD framebuffer driver, x86 reboot fixups
D: pirq addr, CS5535 alsa audio driver
S: Gurgaon, India
S: Kuala Lumpur, Malaysia

Expand Down Expand Up @@ -3202,7 +3203,7 @@ N: Eugene Surovegin
E: ebs@ebshome.net
W: http://kernel.ebshome.net/
P: 1024D/AE5467F1 FF22 39F1 6728 89F6 6E6C 2365 7602 F33D AE54 67F1
D: Embedded PowerPC 4xx: I2C, PIC and random hacks/fixes
D: Embedded PowerPC 4xx: EMAC, I2C, PIC and random hacks/fixes
S: Sunnyvale, California 94085
S: USA

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31 changes: 5 additions & 26 deletions Documentation/Changes
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Expand Up @@ -31,8 +31,6 @@ al espa
Eine deutsche Version dieser Datei finden Sie unter
<http://www.stefan-winter.de/Changes-2.4.0.txt>.

Last updated: October 29th, 2002

Chris Ricker (kaboom@gatech.edu or chris.ricker@genetics.utah.edu).

Current Minimal Requirements
Expand All @@ -48,7 +46,7 @@ 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 2.95.3 # gcc --version
o Gnu C 3.2 # gcc --version
o Gnu make 3.79.1 # make --version
o binutils 2.12 # ld -v
o util-linux 2.10o # fdformat --version
Expand All @@ -74,26 +72,7 @@ GCC
---

The gcc version requirements may vary depending on the type of CPU in your
computer. The next paragraph applies to users of x86 CPUs, but not
necessarily to users of other CPUs. Users of other CPUs should obtain
information about their gcc version requirements from another source.

The recommended compiler for the kernel is gcc 2.95.x (x >= 3), and it
should be used when you need absolute stability. You may use gcc 3.0.x
instead if you wish, although it may cause problems. Later versions of gcc
have not received much testing for Linux kernel compilation, and there are
almost certainly bugs (mainly, but not exclusively, in the kernel) that
will need to be fixed in order to use these compilers. In any case, using
pgcc instead of plain gcc is just asking for trouble.

The Red Hat gcc 2.96 compiler subtree can also be used to build this tree.
You should ensure you use gcc-2.96-74 or later. gcc-2.96-54 will not build
the kernel correctly.

In addition, please pay attention to compiler optimization. Anything
greater than -O2 may not be wise. Similarly, if you choose to use gcc-2.95.x
or derivatives, be sure not to use -fstrict-aliasing (which, depending on
your version of gcc 2.95.x, may necessitate using -fno-strict-aliasing).
computer.

Make
----
Expand Down Expand Up @@ -322,9 +301,9 @@ Getting updated software
Kernel compilation
******************

gcc 2.95.3
----------
o <ftp://ftp.gnu.org/gnu/gcc/gcc-2.95.3.tar.gz>
gcc
---
o <ftp://ftp.gnu.org/gnu/gcc/>

Make
----
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43 changes: 37 additions & 6 deletions Documentation/CodingStyle
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Expand Up @@ -199,7 +199,7 @@ The rationale is:
modifications are prevented
- saves the compiler work to optimize redundant code away ;)

int fun(int )
int fun(int a)
{
int result = 0;
char *buffer = kmalloc(SIZE);
Expand Down Expand Up @@ -344,7 +344,7 @@ Remember: if another thread can find your data structure, and you don't
have a reference count on it, you almost certainly have a bug.


Chapter 11: Macros, Enums, Inline functions and RTL
Chapter 11: Macros, Enums and RTL

Names of macros defining constants and labels in enums are capitalized.

Expand Down Expand Up @@ -429,7 +429,35 @@ from void pointer to any other pointer type is guaranteed by the C programming
language.


Chapter 14: References
Chapter 14: The inline disease

There appears to be a common misperception that gcc has a magic "make me
faster" speedup option called "inline". While the use of inlines can be
appropriate (for example as a means of replacing macros, see Chapter 11), it
very often is not. Abundant use of the inline keyword leads to a much bigger
kernel, which in turn slows the system as a whole down, due to a bigger
icache footprint for the CPU and simply because there is less memory
available for the pagecache. Just think about it; a pagecache miss causes a
disk seek, which easily takes 5 miliseconds. There are a LOT of cpu cycles
that can go into these 5 miliseconds.

A reasonable rule of thumb is to not put inline at functions that have more
than 3 lines of code in them. An exception to this rule are the cases where
a parameter is known to be a compiletime constant, and as a result of this
constantness you *know* the compiler will be able to optimize most of your
function away at compile time. For a good example of this later case, see
the kmalloc() inline function.

Often people argue that adding inline to functions that are static and used
only once is always a win since there is no space tradeoff. While this is
technically correct, gcc is capable of inlining these automatically without
help, and the maintenance issue of removing the inline when a second user
appears outweighs the potential value of the hint that tells gcc to do
something it would have done anyway.



Chapter 15: References

The C Programming Language, Second Edition
by Brian W. Kernighan and Dennis M. Ritchie.
Expand All @@ -444,10 +472,13 @@ ISBN 0-201-61586-X.
URL: http://cm.bell-labs.com/cm/cs/tpop/

GNU manuals - where in compliance with K&R and this text - for cpp, gcc,
gcc internals and indent, all available from http://www.gnu.org
gcc internals and indent, all available from http://www.gnu.org/manual/

WG14 is the international standardization working group for the programming
language C, URL: http://std.dkuug.dk/JTC1/SC22/WG14/
language C, URL: http://www.open-std.org/JTC1/SC22/WG14/

Kernel CodingStyle, by greg@kroah.com at OLS 2002:
http://www.kroah.com/linux/talks/ols_2002_kernel_codingstyle_talk/html/

--
Last updated on 16 February 2004 by a community effort on LKML.
Last updated on 30 December 2005 by a community effort on LKML.
6 changes: 6 additions & 0 deletions Documentation/DocBook/.gitignore
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@@ -0,0 +1,6 @@
*.xml
*.ps
*.pdf
*.html
*.9.gz
*.9
6 changes: 6 additions & 0 deletions Documentation/DocBook/kernel-api.tmpl
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Expand Up @@ -53,6 +53,11 @@
!Iinclude/linux/sched.h
!Ekernel/sched.c
!Ekernel/timer.c
</sect1>
<sect1><title>High-resolution timers</title>
!Iinclude/linux/ktime.h
!Iinclude/linux/hrtimer.h
!Ekernel/hrtimer.c
</sect1>
<sect1><title>Internal Functions</title>
!Ikernel/exit.c
Expand Down Expand Up @@ -369,6 +374,7 @@ X!Edrivers/acpi/motherboard.c
X!Edrivers/acpi/bus.c
-->
!Edrivers/acpi/scan.c
!Idrivers/acpi/scan.c
<!-- No correct structured comments
X!Edrivers/acpi/pci_bind.c
-->
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22 changes: 14 additions & 8 deletions Documentation/DocBook/kernel-locking.tmpl
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Expand Up @@ -222,24 +222,30 @@
<title>Two Main Types of Kernel Locks: Spinlocks and Semaphores</title>

<para>
There are two main types of kernel locks. The fundamental type
There are three main types of kernel locks. The fundamental type
is the spinlock
(<filename class="headerfile">include/asm/spinlock.h</filename>),
which is a very simple single-holder lock: if you can't get the
spinlock, you keep trying (spinning) until you can. Spinlocks are
very small and fast, and can be used anywhere.
</para>
<para>
The second type is a semaphore
The second type is a mutex
(<filename class="headerfile">include/linux/mutex.h</filename>): it
is like a spinlock, but you may block holding a mutex.
If you can't lock a mutex, your task will suspend itself, and be woken
up when the mutex is released. This means the CPU can do something
else while you are waiting. There are many cases when you simply
can't sleep (see <xref linkend="sleeping-things"/>), and so have to
use a spinlock instead.
</para>
<para>
The third type is a semaphore
(<filename class="headerfile">include/asm/semaphore.h</filename>): it
can have more than one holder at any time (the number decided at
initialization time), although it is most commonly used as a
single-holder lock (a mutex). If you can't get a semaphore,
your task will put itself on the queue, and be woken up when the
semaphore is released. This means the CPU will do something
else while you are waiting, but there are many cases when you
simply can't sleep (see <xref linkend="sleeping-things"/>), and so
have to use a spinlock instead.
single-holder lock (a mutex). If you can't get a semaphore, your
task will be suspended and later on woken up - just like for mutexes.
</para>
<para>
Neither type of lock is recursive: see
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1 change: 1 addition & 0 deletions Documentation/DocBook/usb.tmpl
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Expand Up @@ -253,6 +253,7 @@
!Edrivers/usb/core/urb.c
!Edrivers/usb/core/message.c
!Edrivers/usb/core/file.c
!Edrivers/usb/core/driver.c
!Edrivers/usb/core/usb.c
!Edrivers/usb/core/hub.c
</chapter>
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4 changes: 2 additions & 2 deletions Documentation/DocBook/videobook.tmpl
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Expand Up @@ -229,7 +229,7 @@ int __init myradio_init(struct video_init *v)

static int users = 0;

static int radio_open(stuct video_device *dev, int flags)
static int radio_open(struct video_device *dev, int flags)
{
if(users)
return -EBUSY;
Expand Down Expand Up @@ -949,7 +949,7 @@ int __init mycamera_init(struct video_init *v)

static int users = 0;

static int camera_open(stuct video_device *dev, int flags)
static int camera_open(struct video_device *dev, int flags)
{
if(users)
return -EBUSY;
Expand Down
87 changes: 40 additions & 47 deletions Documentation/RCU/rcuref.txt
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@@ -1,74 +1,67 @@
Refcounter framework for elements of lists/arrays protected by
RCU.
Refcounter design for elements of lists/arrays protected by RCU.

Refcounting on elements of lists which are protected by traditional
reader/writer spinlocks or semaphores are straight forward as in:

1. 2.
add() search_and_reference()
{ {
alloc_object read_lock(&list_lock);
... search_for_element
atomic_set(&el->rc, 1); atomic_inc(&el->rc);
write_lock(&list_lock); ...
add_element read_unlock(&list_lock);
... ...
write_unlock(&list_lock); }
1. 2.
add() search_and_reference()
{ {
alloc_object read_lock(&list_lock);
... search_for_element
atomic_set(&el->rc, 1); atomic_inc(&el->rc);
write_lock(&list_lock); ...
add_element read_unlock(&list_lock);
... ...
write_unlock(&list_lock); }
}

3. 4.
release_referenced() delete()
{ {
... write_lock(&list_lock);
atomic_dec(&el->rc, relfunc) ...
... delete_element
} write_unlock(&list_lock);
...
if (atomic_dec_and_test(&el->rc))
kfree(el);
...
... write_lock(&list_lock);
atomic_dec(&el->rc, relfunc) ...
... delete_element
} write_unlock(&list_lock);
...
if (atomic_dec_and_test(&el->rc))
kfree(el);
...
}

If this list/array is made lock free using rcu as in changing the
write_lock in add() and delete() to spin_lock and changing read_lock
in search_and_reference to rcu_read_lock(), the rcuref_get in
in search_and_reference to rcu_read_lock(), the atomic_get in
search_and_reference could potentially hold reference to an element which
has already been deleted from the list/array. rcuref_lf_get_rcu takes
has already been deleted from the list/array. atomic_inc_not_zero takes
care of this scenario. search_and_reference should look as;

1. 2.
add() search_and_reference()
{ {
alloc_object rcu_read_lock();
... search_for_element
atomic_set(&el->rc, 1); if (rcuref_inc_lf(&el->rc)) {
write_lock(&list_lock); rcu_read_unlock();
return FAIL;
add_element }
... ...
write_unlock(&list_lock); rcu_read_unlock();
alloc_object rcu_read_lock();
... search_for_element
atomic_set(&el->rc, 1); if (atomic_inc_not_zero(&el->rc)) {
write_lock(&list_lock); rcu_read_unlock();
return FAIL;
add_element }
... ...
write_unlock(&list_lock); rcu_read_unlock();
} }
3. 4.
release_referenced() delete()
{ {
... write_lock(&list_lock);
rcuref_dec(&el->rc, relfunc) ...
... delete_element
} write_unlock(&list_lock);
...
if (rcuref_dec_and_test(&el->rc))
call_rcu(&el->head, el_free);
...
... write_lock(&list_lock);
atomic_dec(&el->rc, relfunc) ...
... delete_element
} write_unlock(&list_lock);
...
if (atomic_dec_and_test(&el->rc))
call_rcu(&el->head, el_free);
...
}

Sometimes, reference to the element need to be obtained in the
update (write) stream. In such cases, rcuref_inc_lf might be an overkill
since the spinlock serialising list updates are held. rcuref_inc
update (write) stream. In such cases, atomic_inc_not_zero might be an
overkill since the spinlock serialising list updates are held. atomic_inc
is to be used in such cases.
For arches which do not have cmpxchg rcuref_inc_lf
api uses a hashed spinlock implementation and the same hashed spinlock
is acquired in all rcuref_xxx primitives to preserve atomicity.
Note: Use rcuref_inc api only if you need to use rcuref_inc_lf on the
refcounter atleast at one place. Mixing rcuref_inc and atomic_xxx api
might lead to races. rcuref_inc_lf() must be used in lockfree
RCU critical sections only.

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