BMC/Intel-BMC/linux.git/arch/s390/include/asm/percpu.h, branch dev

s390: remove 31 bit support

2015-03-25T10:49:33+00:00

Remove the 31 bit support in order to reduce maintenance cost and effectively remove dead code. Since a couple of years there is no distribution left that comes with a 31 bit kernel. The 31 bit kernel also has been broken since more than a year before anybody noticed. In addition I added a removal warning to the kernel shown at ipl for 5 minutes: a960062e5826 ("s390: add 31 bit warning message") which let everybody know about the plan to remove 31 bit code. We didn't get any response. Given that the last 31 bit only machine was introduced in 1999 let's remove the code. Anybody with 31 bit user space code can still use the compat mode. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390: Replace __get_cpu_var uses

2014-08-26T17:45:52+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) Cc: Martin Schwidefsky CC: linux390@de.ibm.com Acked-by: Heiko Carstens Signed-off-by: Christoph Lameter Signed-off-by: Tejun Heo

s390/percpu: remove this_cpu_xor() implementation

2013-10-31T08:53:58+00:00

this_cpu_xor() will be removed tree wide during the next merge window. To avoid merge conflicts s390's removal comes via the s390 tree. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/percpu: make use of interlocked-access facility 1 instructions

2013-10-24T15:17:13+00:00

Optimize this_cpu_* functions for 64 bit by making use of new instructions that came with the interlocked-access facility 1 (load-and-*) and the general-instructions-extension facility (asi, agsi). That way we get rid of the compare-and-swap loop in most cases. Code size reduction (defconfig, -march=z196): 11,555 bytes. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/percpu: use generic percpu ops for CONFIG_32BIT

2013-10-24T15:17:13+00:00

Remove the special cases for the this_cpu_* functions for 32 bit in order to make it easier to add additional code for 64 bit. 32 bit will use the generic implementation. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/cmpxchg,percpu: implement cmpxchg_double()

2012-09-26T13:45:25+00:00

Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/percpu: implement this_cpu_add_return()

2012-09-26T13:45:25+00:00

Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/percpu: implement this_cpu_xchg()

2012-09-26T13:45:24+00:00

The generic variant has a local_irq_save/restore pair which is quite expensive. It is sufficient to disable preemption, which is a no-op with !CONFIG_PREEMPT and then use the regular xchg macro. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/headers: replace s390x with CONFIG_64BIT where possible

2012-05-24T08:10:10+00:00

Replace __s390x__ with CONFIG_64BIT in all places that are not exported to userspace or guarded with #ifdef __KERNEL__. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

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: