linux-toradex.git/arch/x86/include/asm/percpu.h, branch v3.12.2

percpu: fix this_cpu_sub() subtrahend casting for unsigneds

2013-10-30T21:27:03+00:00

this_cpu_sub() is implemented as negation and addition.

This patch casts the adjustment to the counter type before negation to
sign extend the adjustment.  This helps in cases where the counter type
is wider than an unsigned adjustment.  An alternative to this patch is
to declare such operations unsupported, but it seemed useful to avoid
surprises.

This patch specifically helps the following example:
  unsigned int delta = 1
  preempt_disable()
  this_cpu_write(long_counter, 0)
  this_cpu_sub(long_counter, delta)
  preempt_enable()

Before this change long_counter on a 64 bit machine ends with value
0xffffffff, rather than 0xffffffffffffffff.  This is because
this_cpu_sub(pcp, delta) boils down to this_cpu_add(pcp, -delta),
which is basically:
  long_counter = 0 + 0xffffffff

Also apply the same cast to:
  __this_cpu_sub()
  __this_cpu_sub_return()
  this_cpu_sub_return()

All percpu_test.ko passes, especially the following cases which
previously failed:

  l -= ui_one;
  __this_cpu_sub(long_counter, ui_one);
  CHECK(l, long_counter, -1);

  l -= ui_one;
  this_cpu_sub(long_counter, ui_one);
  CHECK(l, long_counter, -1);
  CHECK(l, long_counter, 0xffffffffffffffff);

  ul -= ui_one;
  __this_cpu_sub(ulong_counter, ui_one);
  CHECK(ul, ulong_counter, -1);
  CHECK(ul, ulong_counter, 0xffffffffffffffff);

  ul = this_cpu_sub_return(ulong_counter, ui_one);
  CHECK(ul, ulong_counter, 2);

  ul = __this_cpu_sub_return(ulong_counter, ui_one);
  CHECK(ul, ulong_counter, 1);

Signed-off-by: Greg Thelen 
Acked-by: Tejun Heo 
Acked-by: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

x86, 386 removal: Remove CONFIG_CMPXCHG

2012-11-29T21:23:01+00:00

All 486+ CPUs support CMPXCHG, so remove the fallback 386 support
code.

Signed-off-by: H. Peter Anvin 
Link: http://lkml.kernel.org/r/1354132230-21854-3-git-send-email-hpa@linux.intel.com

x86: Define early read-mostly per-cpu macros

2012-06-14T10:42:10+00:00

Some read-mostly per-cpu data may need to be declared or defined
early, so it can be initialized and accessed before per_cpu
areas are allocated.

Only the data that resides in the per_cpu areas should be
read-mostly, as there is little benefit in optimizing cache
lines on initialization.

Signed-off-by: Ido Yariv 
[ Added the missing declarations in !SMP code. ]
Signed-off-by: Vlad Zolotarov 
Acked-by: Shai Fultheim 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/46188571.ddB8aVQYWo@vlad
Signed-off-by: Ingo Molnar

percpu: remove percpu_xxx() functions

2012-05-14T21:15:32+00:00

Remove percpu_xxx serial functions, all of them were replaced by
this_cpu_xxx or __this_cpu_xxx serial functions

Signed-off-by: Alex Shi 
Acked-by: Christoph Lameter 
Acked-by: Tejun Heo 
Acked-by: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Tejun Heo

x86: replace percpu_xxx funcs with this_cpu_xxx

2012-05-14T21:15:31+00:00

Since percpu_xxx() serial functions are duplicated with this_cpu_xxx().
Removing percpu_xxx() definition and replacing them by this_cpu_xxx()
in code. There is no function change in this patch, just preparation for
later percpu_xxx serial function removing.

On x86 machine the this_cpu_xxx() serial functions are same as
__this_cpu_xxx() without no unnecessary premmpt enable/disable.

Thanks for Stephen Rothwell, he found and fixed a i386 build error in
the patch.

Also thanks for Andrew Morton, he kept updating the patchset in Linus'
tree.

Signed-off-by: Alex Shi 
Acked-by: Christoph Lameter 
Acked-by: Tejun Heo 
Acked-by: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: Thomas Gleixner 
Signed-off-by: Stephen Rothwell 
Signed-off-by: Andrew Morton 
Signed-off-by: Tejun Heo

Merge branch 'for-3.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu

2012-01-09T21:08:28+00:00

* 'for-3.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu:
  percpu: Remove irqsafe_cpu_xxx variants

Fix up conflict in arch/x86/include/asm/percpu.h due to clash with
cebef5beed3d ("x86: Fix and improve percpu_cmpxchg{8,16}b_double()")
which edited the (now removed) irqsafe_cpu_cmpxchg*_double code.

percpu: Remove irqsafe_cpu_xxx variants

2011-12-22T18:40:20+00:00

We simply say that regular this_cpu use must be safe regardless of
preemption and interrupt state.  That has no material change for x86
and s390 implementations of this_cpu operations.  However, arches that
do not provide their own implementation for this_cpu operations will
now get code generated that disables interrupts instead of preemption.

-tj: This is part of on-going percpu API cleanup.  For detailed
     discussion of the subject, please refer to the following thread.

     http://thread.gmane.org/gmane.linux.kernel/1222078

Signed-off-by: Christoph Lameter 
Signed-off-by: Tejun Heo 
LKML-Reference:

x86: Fix and improve percpu_cmpxchg{8,16}b_double()

2011-12-15T07:17:14+00:00

They had several problems/shortcomings:

Only the first memory operand was mentioned in the 2x32bit asm()
operands, and 2x64-bit version had a memory clobber. The first
allowed the compiler to not recognize the need to re-load the
data in case it had it cached in some register, and the second
was overly destructive.

The memory operand in the 2x32-bit asm() was declared to only be
an output.

The types of the local copies of the old and new values were
incorrect (as in other per-CPU ops, the types of the per-CPU
variables accessed should be used here, to make sure the
respective types are compatible).

The __dummy variable was pointless (and needlessly initialized
in the 2x32-bit case), given that local copies of the inputs
already exist.

The 2x64-bit variant forced the address of the first object into
%rsi, even though this is needed only for the call to the
emulation function. The real cmpxchg16b can operate on an
memory.

At once also change the return value type to what it really is -
'bool'.

Signed-off-by: Jan Beulich 
Cc: Linus Torvalds 
Cc: Andrew Morton 
Cc: David Howells 
Cc: Christoph Lameter 
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/4EE86D6502000078000679FE@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar

percpu: Fixup __this_cpu_xchg* operations

2011-07-12T11:47:16+00:00

Somehow we got into a situation where the __this_cpu_xchg() operations were
not defined in the same way as this_cpu_xchg() and friends. I had some build
failures under 32 bit that were addressed by these fixes.

Signed-off-by: Christoph Lameter 
Signed-off-by: Tejun Heo

Merge branch 'for-2.6.40' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu

2011-05-24T18:53:42+00:00

* 'for-2.6.40' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu:
  percpu: Unify input section names
  percpu: Avoid extra NOP in percpu_cmpxchg16b_double
  percpu: Cast away printk format warning
  percpu: Always align percpu output section to PAGE_SIZE

Fix up fairly trivial conflict in arch/x86/include/asm/percpu.h as per Tejun