linux-stable.git/arch/powerpc/include/asm/percpu.h, branch linux-4.4.y

powerpc: Fix circular dependency between percpu.h and mmu.h

2020-08-21T08:53:05+00:00

commit 0c83b277ada72b585e6a3e52b067669df15bcedb upstream.

Recently random.h started including percpu.h (see commit
f227e3ec3b5c ("random32: update the net random state on interrupt and
activity")), which broke corenet64_smp_defconfig:

  In file included from /linux/arch/powerpc/include/asm/paca.h:18,
                   from /linux/arch/powerpc/include/asm/percpu.h:13,
                   from /linux/include/linux/random.h:14,
                   from /linux/lib/uuid.c:14:
  /linux/arch/powerpc/include/asm/mmu.h:139:22: error: unknown type name 'next_tlbcam_idx'
    139 | DECLARE_PER_CPU(int, next_tlbcam_idx);

This is due to a circular header dependency:
  asm/mmu.h includes asm/percpu.h, which includes asm/paca.h, which
  includes asm/mmu.h

Which means DECLARE_PER_CPU() isn't defined when mmu.h needs it.

We can fix it by moving the include of paca.h below the include of
asm-generic/percpu.h.

This moves the include of paca.h out of the #ifdef __powerpc64__, but
that is OK because paca.h is almost entirely inside #ifdef
CONFIG_PPC64 anyway.

It also moves the include of paca.h out of the #ifdef CONFIG_SMP,
which could possibly break something, but seems to have no ill
effects.

Fixes: f227e3ec3b5c ("random32: update the net random state on interrupt and activity")
Cc: stable@vger.kernel.org # v5.8
Reported-by: Stephen Rothwell 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20200804130558.292328-1-mpe@ellerman.id.au
Signed-off-by: Greg Kroah-Hartman

powerpc: Optimise per cpu accesses on 64bit

2010-07-09T01:28:30+00:00

Now we dynamically allocate the paca array, it takes an extra load
whenever we want to access another cpu's paca. One place we do that a lot
is per cpu variables. A simple example:

DEFINE_PER_CPU(unsigned long, vara);
unsigned long test4(int cpu)
{
	return per_cpu(vara, cpu);
}

This takes 4 loads, 5 if you include the actual load of the per cpu variable:

    ld r11,-32760(r30)  # load address of paca pointer
    ld r9,-32768(r30)   # load link address of percpu variable
    sldi r3,r29,9       # get offset into paca (each entry is 512 bytes)
    ld r0,0(r11)        # load paca pointer
    add r3,r0,r3        # paca + offset
    ld r11,64(r3)       # load paca[cpu].data_offset

    ldx r3,r9,r11       # load per cpu variable

If we remove the ppc64 specific per_cpu_offset(), we get the generic one
which indexes into a statically allocated array. This removes one load and
one add:

    ld r11,-32760(r30)  # load address of __per_cpu_offset
    ld r9,-32768(r30)   # load link address of percpu variable
    sldi r3,r29,3       # get offset into __per_cpu_offset (each entry 8 bytes)
    ldx r11,r11,r3      # load __per_cpu_offset[cpu]

    ldx r3,r9,r11       # load per cpu variable

Having all the offsets in one array also helps when iterating over a per cpu
variable across a number of cpus, such as in the scheduler. Before we would
need to load one paca cacheline when calculating each per cpu offset. Now we
have 16 (128 / sizeof(long)) per cpu offsets in each cacheline.

Signed-off-by: Anton Blanchard 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Move include files to arch/powerpc/include/asm

2008-08-04T02:02:00+00:00

from include/asm-powerpc.  This is the result of a

mkdir arch/powerpc/include/asm
git mv include/asm-powerpc/* arch/powerpc/include/asm

Followed by a few documentation/comment fixups and a couple of places
where  was being used explicitly.  Of the latter only
one was outside the arch code and it is a driver only built for powerpc.

Signed-off-by: Stephen Rothwell 
Signed-off-by: Paul Mackerras