linux-toradex.git/arch/sh/kernel/smp.c, branch v4.2.7

Fix weird uses of num_online_cpus().

2015-03-10T03:24:42+00:00

This may be OK in archs with contiguous CPU numbers and without
hotplug CPUs, but it sets a terrible example.

And open-coding it like drivers/scsi/hpsa.c is just weird.

BTRFS has a weird comparison with num_online_cpus() too, but since
BTRFS just screwed up my test machines' root partition, I'm not
touching it :)

Signed-off-by: Rusty Russell 
Reported-by: Oleg Drokin

sh: Replace __get_cpu_var uses

2014-06-04T23:53:52+00:00

__get_cpu_var() is used for multiple purposes in the kernel source.  One
of them is address calculation via the form &__get_cpu_var(x).  This
calculates the address for the instance of the percpu variable of the
current processor based on an offset.

Other use cases are for storing and retrieving data from the current
processors percpu area.  __get_cpu_var() can be used as an lvalue when
writing data or on the right side of an assignment.

__get_cpu_var() is defined as :

#define __get_cpu_var(var) (*this_cpu_ptr(&(var)))

__get_cpu_var() always only does an address determination.  However, store
and retrieve operations could use a segment prefix (or global register on
other platforms) to avoid the address calculation.

this_cpu_write() and this_cpu_read() can directly take an offset into a
percpu area and use optimized assembly code to read and write per cpu
variables.

This patch converts __get_cpu_var into either an explicit address
calculation using this_cpu_ptr() or into a use of this_cpu operations that
use the offset.  Thereby address calculations are avoided and less
registers are used when code is generated.

At the end of the patch set all uses of __get_cpu_var have been removed so
the macro is removed too.

The patch set includes passes over all arches as well.  Once these
operations are used throughout then specialized macros can be defined in
non -x86 arches as well in order to optimize per cpu access by f.e.  using
a global register that may be set to the per cpu base.

Transformations done to __get_cpu_var()

1. Determine the address of the percpu instance of the current processor.

	DEFINE_PER_CPU(int, y);
	int *x = &__get_cpu_var(y);

    Converts to

	int *x = this_cpu_ptr(&y);

2. Same as #1 but this time an array structure is involved.

	DEFINE_PER_CPU(int, y[20]);
	int *x = __get_cpu_var(y);

    Converts to

	int *x = this_cpu_ptr(y);

3. Retrieve the content of the current processors instance of a per cpu
variable.

	DEFINE_PER_CPU(int, y);
	int x = __get_cpu_var(y)

   Converts to

	int x = __this_cpu_read(y);

4. Retrieve the content of a percpu struct

	DEFINE_PER_CPU(struct mystruct, y);
	struct mystruct x = __get_cpu_var(y);

   Converts to

	memcpy(&x, this_cpu_ptr(&y), sizeof(x));

5. Assignment to a per cpu variable

	DEFINE_PER_CPU(int, y)
	__get_cpu_var(y) = x;

   Converts to

	__this_cpu_write(y, x);

6. Increment/Decrement etc of a per cpu variable

	DEFINE_PER_CPU(int, y);
	__get_cpu_var(y)++

   Converts to

	__this_cpu_inc(y)

Signed-off-by: Christoph Lameter 
Tested-by: Geert Uytterhoeven  [compilation only]
Cc: Paul Mundt 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sh: delete __cpuinit usage from all sh files

2013-07-14T23:36:53+00:00

The __cpuinit type of throwaway sections might have made sense
some time ago when RAM was more constrained, but now the savings
do not offset the cost and complications.  For example, the fix in
commit 5e427ec2d0 ("x86: Fix bit corruption at CPU resume time")
is a good example of the nasty type of bugs that can be created
with improper use of the various __init prefixes.

After a discussion on LKML[1] it was decided that cpuinit should go
the way of devinit and be phased out.  Once all the users are gone,
we can then finally remove the macros themselves from linux/init.h.

Note that some harmless section mismatch warnings may result, since
notify_cpu_starting() and cpu_up() are arch independent (kernel/cpu.c)
are flagged as __cpuinit  -- so if we remove the __cpuinit from
arch specific callers, we will also get section mismatch warnings.
As an intermediate step, we intend to turn the linux/init.h cpuinit
content into no-ops as early as possible, since that will get rid
of these warnings.  In any case, they are temporary and harmless.

This removes all the arch/sh uses of the __cpuinit macros from
all C files.  Currently sh does not have any __CPUINIT used in
assembly files.

[1] https://lkml.org/lkml/2013/5/20/589

Cc: Paul Mundt 
Cc: linux-sh@vger.kernel.org
Signed-off-by: Paul Gortmaker

sh: Use generic idle loop

2013-04-08T15:39:28+00:00

Signed-off-by: Thomas Gleixner 
Cc: Linus Torvalds 
Cc: Rusty Russell 
Cc: Paul McKenney 
Cc: Peter Zijlstra 
Reviewed-by: Cc: Srivatsa S. Bhat 
Cc: Magnus Damm 
Cc: Paul Mundt 
Link: http://lkml.kernel.org/r/20130321215235.216323644@linutronix.de
Signed-off-by: Thomas Gleixner

sh: use clear_tasks_mm_cpumask()

2012-06-01T00:49:30+00:00

Checking for process->mm is not enough because process' main thread may
exit or detach its mm via use_mm(), but other threads may still have a
valid mm.

To fix this we would need to use find_lock_task_mm(), which would walk up
all threads and returns an appropriate task (with task lock held).

clear_tasks_mm_cpumask() has the issue fixed, so let's use it.

Suggested-by: Oleg Nesterov 
Signed-off-by: Anton Vorontsov 
Cc: Paul Mundt 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sh: Use generic idle thread allocation

2012-04-26T10:06:12+00:00

Signed-off-by: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Rusty Russell 
Cc: Paul E. McKenney 
Cc: Srivatsa S. Bhat 
Acked-by: Paul Mundt 
Link: http://lkml.kernel.org/r/20120420124557.855203626@linutronix.de

smp: Add task_struct argument to __cpu_up()

2012-04-26T10:06:09+00:00

Preparatory patch to make the idle thread allocation for secondary
cpus generic.

Signed-off-by: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Rusty Russell 
Cc: Paul E. McKenney 
Cc: Srivatsa S. Bhat 
Cc: Matt Turner 
Cc: Russell King 
Cc: Mike Frysinger 
Cc: Jesper Nilsson 
Cc: Richard Kuo 
Cc: Tony Luck 
Cc: Hirokazu Takata 
Cc: Ralf Baechle 
Cc: David Howells 
Cc: James E.J. Bottomley 
Cc: Benjamin Herrenschmidt 
Cc: Martin Schwidefsky 
Cc: Paul Mundt 
Cc: David S. Miller 
Cc: Chris Metcalf 
Cc: Richard Weinberger 
Cc: x86@kernel.org
Link: http://lkml.kernel.org/r/20120420124556.964170564@linutronix.de

sh: fix up fallout from system.h disintegration.

2012-03-30T10:29:57+00:00

Quite a bit of fallout all over the place, nothing terribly exciting.

Signed-off-by: Paul Mundt

Disintegrate asm/system.h for SH

2012-03-28T17:30:03+00:00

Disintegrate asm/system.h for SH.

Signed-off-by: David Howells 
cc: linux-sh@vger.kernel.org

arch/sh: remove references to cpu_*_map.

2012-02-24T04:21:45+00:00

This has been obsolescent for a while; time for the final push.

Signed-off-by: Rusty Russell 
Cc: Paul Mundt 
Cc: linux-sh@vger.kernel.org
Signed-off-by: Paul Mundt