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Using GCC_VERSION reduces complexity, is easier to read and is GCC's
recommended mechanism for doing version checks. (Just don't ask me why
they didn't define it in the first place.) This also makes it easy to
merge compiler-gcc{,3,4}.h should somebody want to.
Signed-off-by: Daniel Santos <daniel.santos@pobox.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Joe Perches <joe@perches.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Unify identical gcc3.x and gcc4.x macros.
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Enable the use of GCC's coverage testing tool gcov [1] with the Linux
kernel. gcov may be useful for:
* debugging (has this code been reached at all?)
* test improvement (how do I change my test to cover these lines?)
* minimizing kernel configurations (do I need this option if the
associated code is never run?)
The profiling patch incorporates the following changes:
* change kbuild to include profiling flags
* provide functions needed by profiling code
* present profiling data as files in debugfs
Note that on some architectures, enabling gcc's profiling option
"-fprofile-arcs" for the entire kernel may trigger compile/link/
run-time problems, some of which are caused by toolchain bugs and
others which require adjustment of architecture code.
For this reason profiling the entire kernel is initially restricted
to those architectures for which it is known to work without changes.
This restriction can be lifted once an architecture has been tested
and found compatible with gcc's profiling. Profiling of single files
or directories is still available on all platforms (see config help
text).
[1] http://gcc.gnu.org/onlinedocs/gcc/Gcov.html
Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Li Wei <W.Li@Sun.COM>
Cc: Michael Ellerman <michaele@au1.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Heiko Carstens <heicars2@linux.vnet.ibm.com>
Cc: Martin Schwidefsky <mschwid2@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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GCC 3.0 and 3.1 are too old to build a working kernel.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
[ This check got dropped as obsolete when I simplified the gcc header
inclusion mess in f153b82121b0366fe0e5f9553545cce237335175, but Willy
Tarreau reports actually having those old versions still.. -Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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- include the gcc version-dependent header files from the generic gcc
header file, rather than the other way around (iow: don't make the
non-gcc header file have to know about gcc versions)
- don't include compiler-gcc4.h for gcc 5 (for whenever it gets
released). That's just confusing and made us do odd things in the
gcc4 header file (testing that we really had version 4!)
- generate the name from the __GNUC__ version directly, rather than
having a mess of #if conditionals.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Remove the deprecated __attribute_used__.
[Introduce __section in a few places to silence checkpatch /sam]
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
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Replace worthless comments with actual preprocessor errors when including
the wrong versions of the compiler.h files.
[akpm@linux-foundation.org: make it work]
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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__used is defined to be __attribute__((unused)) for all pre-3.3 gcc
compilers to suppress warnings for unused functions because perhaps they
are referenced only in inline assembly. It is defined to be
__attribute__((used)) for gcc 3.3 and later so that the code is still
emitted for such functions.
__maybe_unused is defined to be __attribute__((unused)) for both function
and variable use if it could possibly be unreferenced due to the evaluation
of preprocessor macros. Function prototypes shall be marked with
__maybe_unused if the actual definition of the function is dependant on
preprocessor macros.
No update to compiler-intel.h is necessary because ICC supports both
__attribute__((used)) and __attribute__((unused)) as specified by the gcc
manual.
__attribute_used__ is deprecated and will be removed once all current
code is converted to using __used.
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Adrian Bunk <bunk@stusta.de>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Introduce a macro for suppressing gcc from generating a warning about a
probable uninitialized state of a variable.
Example:
- spinlock_t *ptl;
+ spinlock_t *uninitialized_var(ptl);
Not a happy solution, but those warnings are obnoxious.
- Using the usual pointlessly-set-it-to-zero approach wastes several
bytes of text.
- Using a macro means we can (hopefully) do something else if gcc changes
cause the `x = x' hack to stop working
- Using a macro means that people who are worried about hiding true bugs
can easily turn it off.
Signed-off-by: Borislav Petkov <bbpetkov@yahoo.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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This patch is the first in a series that tries to optimize the kernel in terms
of size (and thus cache behavior, both cpu and pagecache).
This first patch changes __always_inline to be a forced inline instead of the
"regular" inline it was on everything except alpha. This forced inline
matches the intention of the define better as a matter of documentation.
There is no change in behavior by this patch, since "inline" currently is
mapped to a forced inline anyway.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Remove various things which were checking for gcc-1.x and gcc-2.x compilers.
From: Adrian Bunk <bunk@stusta.de>
Some documentation updates and removes some code paths for gcc < 3.2.
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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With the release of gcc 4.0 being only a few months away and people
already tring compiling with it, it's time for adding a compiler-gcc4.h .
This patch contains the following changes:
- remove compiler-gcc+.h
- compiler-gcc4.h: new file based on a corrected compiler-gcc+.h
- compiler.h: include compiler-gcc4.h for gcc 4
- compiler.h: #error for gcc > 4
- compiler-gcc3.h: remove __compiler_offsetof (there will never be a
gcc 3.5)
small indention corrections
I've tested the compilation with both gcc 3.4.4 and a recent gcc 4.0
snapshot from Debian experimental.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Current gcc 3.5 doesn't compile a x86-64 kernel, because it doesn't
recognize the offsetof used in asm-offset.c to be constant.
Use __builtin_offsetof for this instead.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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I find it somewhat annoying that the preprocessor expands every "inline" to
"__inline__ __attribute__((always_inline)) __attribute__((always_inline))"
in the current code.
Fix that up.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Rationale:
- if gcc 3.4 can't inline a function marked as "inline" that's a strong
hint that further investigation is required
- I strongly prefer a compile error over a potential runtime problem
Signed-off-by: Adrian Bunk <bunk@fs.tum.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Trivial gcc-3.5 build fixes.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The patch below uses the new-in-gcc-3.4 option to generate a warning on
unchecked results of marked functions, and applies this to the
inode_setattr function (which based on recent bk commits HAS to be checked
for it's return value for correct operation). A warning looks like this:
fs/ext2/inode.c:1279: warning: ignoring return value of 'inode_setattr', declared with attribute warn_unused_result
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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From: Arjan van de Ven <arjanv@redhat.com>
Below is a patch to enable 4Kb stacks for x86. The goal of this is to
1) Reduce footprint per thread so that systems can run many more threads
(for the java people)
2) Reduce the pressure on the VM for order > 0 allocations. We see real life
workloads (granted with 2.4 but the fundamental fragmentation issue isn't
solved in 2.6 and isn't solvable in theory) where this can be a problem.
In addition order > 0 allocations can make the VM "stutter" and give more
latency due to having to do much much more work trying to defragment
The first 2 bits of the patch actually affect compiler options in a generic
way: I propose to disable the -funit-at-a-time feature from gcc. With this
enabled (and it's default with -O2), gcc will very agressively inline
functions, which is nice and all for userspace, but for the kernel this makes
us suffer a gcc deficiency more: gcc is extremely bad at sharing stackslots,
for example a situation like this:
if (some_condition)
function_A();
else
function_B();
with -funit-at-a-time, both function_A() and _B() might get inlined, however
the stack usage of both functions of the parent function grows the stack
usage of both functions COMBINED instead of the maximum of the two. Even
with the normal 8Kb stacks this is a danger since we see some functions grow
3Kb to 4Kb of stack use this way. With 4Kb stacks, 4Kb of stack usage growth
obviously is deadly ;-( but even with 8Kb stacks it's pure lottery.
Disabling -funit-at-a-time also exposes another thing in the -mm tree; the
attribute always_inline is considered harmful by gcc folks in that when gcc
makes a decision to NOT inline a function marked this way, it throws an
error. Disabling -funit-at-a-time disables some of the agressive inlining
(eg of large functions that come later in the .c file) so this would make
your tree not compile.
The 4k stackness of the kernel is included in modversions, so people don't
load 4k-stack modules into 8k-stack kernels.
At present 4k stacks are selectable in config. When the feature has settled
in we should remove the 8k option. This will break the nvidia modules. But
Fedora uses 4k stacks so a new nvidia driver is expected soon.
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From: Andi Kleen <ak@muc.de>
This patch adds the `noinline' function attribute. It can be used to
explicitly tell the compiler to not inline functions.
We need this due to what is, IMO, a bug present in gcc-3.4 and current
gcc-3.5 CVS: the compiler is inlining init/main.c:rest_init() inside
init/main.c:start_kernel(), despite the fact that thay are declared to be
placed in different text sections.
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From: "H. Peter Anvin" <hpa@zytor.com>
Declaring a function to return a const scalar value is pretty meaningless.
These functions are really trying to say that they don't alter any external
state.
Fix that up by using __attribute__((const)), if the compiler supports that.
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From: "Nakajima, Jun" <jun.nakajima@intel.com>
Split the increasingly messy compiler.h file into per-compiler files and also
add support for non-gcc compilers.
With the current implementation:
include/linux/compiler.h defines the compiler-dependent abstractions
which can be overwritten by per-compiler definitions.
include/linux/compiler-gcc.h contains the common definitions for all gcc
versions.
include/linux/compiler-gcc[2,3,+].h contains gcc major version specific
definitions.
include/linux/compiler-intel.h contains intel compiler specific
definitions."
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