linux-toradex.git/include/linux/kernel.h, branch v3.7.3

linux/kernel.h: fix DIV_ROUND_CLOSEST with unsigned divisors

2013-01-11T17:19:05+00:00

commit c4e18497d8fd92eef2c6e7eadcc1a107ccd115ea upstream.

Commit 263a523d18bc ("linux/kernel.h: Fix warning seen with W=1 due to
change in DIV_ROUND_CLOSEST") fixes a warning seen with W=1 due to
change in DIV_ROUND_CLOSEST.

Unfortunately, the C compiler converts divide operations with unsigned
divisors to unsigned, even if the dividend is signed and negative (for
example, -10 / 5U = 858993457).  The C standard says "If one operand has
unsigned int type, the other operand is converted to unsigned int", so
the compiler is not to blame.  As a result, DIV_ROUND_CLOSEST(0, 2U) and
similar operations now return bad values, since the automatic conversion
of expressions such as "0 - 2U/2" to unsigned was not taken into
account.

Fix by checking for the divisor variable type when deciding which
operation to perform.  This fixes DIV_ROUND_CLOSEST(0, 2U), but still
returns bad values for negative dividends divided by unsigned divisors.
Mark the latter case as unsupported.

One observed effect of this problem is that the s2c_hwmon driver reports
a value of 4198403 instead of 0 if the ADC reads 0.

Other impact is unpredictable.  Problem is seen if the divisor is an
unsigned variable or constant and the dividend is less than (divisor/2).

Signed-off-by: Guenter Roeck 
Reported-by: Juergen Beisert 
Tested-by: Juergen Beisert 
Cc: Jean Delvare 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

linux/kernel.h: define SYMBOL_PREFIX

2012-12-03T02:35:54+00:00

Define SYMBOL_PREFIX to be the same as CONFIG_SYMBOL_PREFIX if set by
the architecture, or "" otherwise. This avoids the need for ugly #ifdefs
whenever symbols are referenced in asm blocks.

Signed-off-by: James Hogan 
Cc: Andrew Morton 
Cc: Joe Perches 
Cc: Paul Gortmaker 
Cc: Jean Delvare 
Cc: Ralf Baechle 
Cc: Mike Frysinger 
Signed-off-by: Rusty Russell

UAPI: (Scripted) Disintegrate include/linux

2012-10-13T09:46:48+00:00

Signed-off-by: David Howells 
Acked-by: Arnd Bergmann 
Acked-by: Thomas Gleixner 
Acked-by: Michael Kerrisk 
Acked-by: Paul E. McKenney 
Acked-by: Dave Jones

linux/kernel.h: Fix warning seen with W=1 due to change in DIV_ROUND_CLOSEST

2012-09-19T13:51:25+00:00

After commit b6d86d3d (Fix DIV_ROUND_CLOSEST to support negative dividends),
the following warning is seen if the kernel is compiled with W=1 (-Wextra):

warning: comparison of unsigned expression >= 0 is always true

The warning is due to the test '((typeof(x))-1) >= 0', which is used to detect
if the variable type is unsigned. Research on the web suggests that the warning
disappears if '>' instead of '>=' is used for the comparison.

Tests after changing the macro along that line show that the warning is gone,
and that the result is still correct:

i=-4: DIV_ROUND_CLOSEST(i, 2)=-2
i=-3: DIV_ROUND_CLOSEST(i, 2)=-2
i=-2: DIV_ROUND_CLOSEST(i, 2)=-1
i=-1: DIV_ROUND_CLOSEST(i, 2)=-1
i=0: DIV_ROUND_CLOSEST(i, 2)=0
i=1: DIV_ROUND_CLOSEST(i, 2)=1
i=2: DIV_ROUND_CLOSEST(i, 2)=1
i=3: DIV_ROUND_CLOSEST(i, 2)=2
i=4: DIV_ROUND_CLOSEST(i, 2)=2

Code size is the same as before.

Signed-off-by: Guenter Roeck 
Tested-by: Mauro Carvalho Chehab 
Acked-by: Jean Delvare

linux/kernel.h: Fix DIV_ROUND_CLOSEST to support negative dividends

2012-09-02T01:58:09+00:00

DIV_ROUND_CLOSEST returns a bad result for negative dividends:
	DIV_ROUND_CLOSEST(-2, 2) = 0

Most of the time this does not matter. However, in the hardware monitoring
subsystem, DIV_ROUND_CLOSEST is sometimes used on integers which can be
negative (such as temperatures).

Signed-off-by: Guenter Roeck 
Acked-by: Jean Delvare

Remove SYSTEM_SUSPEND_DISK system state

2012-07-21T20:58:17+00:00

The SYSTEM_SUSPEND_DISK system state is never used, so drop it.

Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Linus Torvalds

introduce SIZE_MAX

2012-06-01T00:49:26+00:00

ULONG_MAX is often used to check for integer overflow when calculating
allocation size.  While ULONG_MAX happens to work on most systems, there
is no guarantee that `size_t' must be the same size as `long'.

This patch introduces SIZE_MAX, the maximum value of `size_t', to improve
portability and readability for allocation size validation.

Signed-off-by: Xi Wang 
Acked-by: Alex Elder 
Cc: David Airlie 
Cc: Pekka Enberg 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc

2012-05-24T22:10:28+00:00

Pull sparc changes from David S. Miller:
 "This has the generic strncpy_from_user() implementation architectures
  can now use, which we've been developing on linux-arch over the past
  few days.

  For good measure I ran both a 32-bit and a 64-bit glibc testsuite run,
  and the latter of which pointed out an adjustment I needed to make to
  sparc's user_addr_max() definition.  Linus, you were right, STACK_TOP
  was not the right thing to use, even on sparc itself :-)

  From Sam Ravnborg, we have a conversion of sparc32 over to the common
  alloc_thread_info_node(), since the aspect which originally blocked
  our doing so (sun4c) has been removed."

Fix up trivial arch/sparc/Kconfig and lib/Makefile conflicts.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc:
  sparc: Fix user_addr_max() definition.
  lib: Sparc's strncpy_from_user is generic enough, move under lib/
  kernel: Move REPEAT_BYTE definition into linux/kernel.h
  sparc: Increase portability of strncpy_from_user() implementation.
  sparc: Optimize strncpy_from_user() zero byte search.
  sparc: Add full proper error handling to strncpy_from_user().
  sparc32: use the common implementation of alloc_thread_info_node()

kernel: Move REPEAT_BYTE definition into linux/kernel.h

2012-05-24T20:10:05+00:00

And make sure that everything using it explicitly includes
that header file.

Signed-off-by: David S. Miller

tracing: Add percpu buffers for trace_printk()

2012-04-24T01:15:55+00:00

Currently, trace_printk() uses a single buffer to write into
to calculate the size and format needed to save the trace. To
do this safely in an SMP environment, a spin_lock() is taken
to only allow one writer at a time to the buffer. But this could
also affect what is being traced, and add synchronization that
would not be there otherwise.

Ideally, using percpu buffers would be useful, but since trace_printk()
is only used in development, having per cpu buffers for something
never used is a waste of space. Thus, the use of the trace_bprintk()
format section is changed to be used for static fmts as well as dynamic ones.
Then at boot up, we can check if the section that holds the trace_printk
formats is non-empty, and if it does contain something, then we
know a trace_printk() has been added to the kernel. At this time
the trace_printk per cpu buffers are allocated. A check is also
done at module load time in case a module is added that contains a
trace_printk().

Once the buffers are allocated, they are never freed. If you use
a trace_printk() then you should know what you are doing.

A buffer is made for each type of context:

  normal
  softirq
  irq
  nmi

The context is checked and the appropriate buffer is used.
This allows for totally lockless usage of trace_printk(),
and they no longer even disable interrupts.

Requested-by: Peter Zijlstra 
Signed-off-by: Steven Rostedt