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  1. 30 Sep, 2016 2 commits
    • Arnd Bergmann's avatar
      Fix build warning in kernel/cpuset.c · 29bd0359
      Arnd Bergmann authored 
      >           2 ../kernel/cpuset.c:2101:11: warning: initialization from incompatible pointer type [-Wincompatible-pointer-types]
>           1 ../kernel/cpuset.c:2101:2: warning: initialization from incompatible pointer type
>           1 ../kernel/cpuset.c:2101:2: warning: (near initialization for 'cpuset_cgrp_subsys.fork')

This got introduced by 06ec7a1d ("cpuset: make sure new tasks
conform to the current config of the cpuset"). In the upstream
kernel, the function prototype was changed as of b53202e6
("cgroup: kill cgrp_ss_priv[CGROUP_CANFORK_COUNT] and friends").

That patch is not suitable for stable kernels, and fortunately
the warning seems harmless as the prototypes only differ in the
second argument that is unused. Adding that argument gets rid
of the warning:
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      29bd0359
    • Michal Nazarewicz's avatar
      include/linux/kernel.h: change abs() macro so it uses consistent return type · df127725
      Michal Nazarewicz authored 
      commit 8f57e4d9 upstream.

Rewrite abs() so that its return type does not depend on the
architecture and no unexpected type conversion happen inside of it.  The
only conversion is from unsigned to signed type.  char is left as a
return type but treated as a signed type regradless of it's actual
signedness.

With the old version, int arguments were promoted to long and depending
on architecture a long argument might result in s64 or long return type
(which may or may not be the same).

This came after some back and forth with Nicolas.  The current macro has
different return type (for the same input type) depending on
architecture which might be midly iritating.

An alternative version would promote to int like so:

	#define abs(x)	__abs_choose_expr(x, long long,			\
			__abs_choose_expr(x, long,			\
			__builtin_choose_expr(				\
				sizeof(x) <= sizeof(int),		\
				({ int __x = (x); __x<0?-__x:__x; }),	\
				((void)0))))

I have no preference but imagine Linus might.  :] Nicolas argument against
is that promoting to int causes iconsistent behaviour:

	int main(void) {
		unsigned short a = 0, b = 1, c = a - b;
		unsigned short d = abs(a - b);
		unsigned short e = abs(c);
		printf("%u %u\n", d, e);  // prints: 1 65535
	}

Then again, no sane person expects consistent behaviour from C integer
arithmetic.  ;)

Note:

  __builtin_types_compatible_p(unsigned char, char) is always false, and
  __builtin_types_compatible_p(signed char, char) is also always false.
Signed-off-by: default avatarMichal Nazarewicz <mina86@mina86.com>
Reviewed-by: default avatarNicolas Pitre <nico@linaro.org>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      df127725
  3. 24 Sep, 2016 38 commits
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