linux/arch/s390
Christian Borntraeger 1afc82aee4 s390/barrier: avoid serialization in [smp_]rmb and [smp_]wmb
The principles of operation says:

The storage-operand fetch references of one instruction
occur after those of all preceding instructions and
before those of subsequent instructions, as observed
by other CPUs and by channel programs.
[...]
The CPU may fetch the operands of instructions before the
instructions are executed.
[...]
The CPU may delay placing results in storage.
[...]
the results of one instruction are placed in storage after
the results of all preceding instructions have been placed
in storage and before any results of the succeeding
instructions are stored, as observed by other CPUs and by
the channel subsystem.

which boils down to:
- reads are in order
- writes are in order
- reads can happen earlier
- writes can happen later

By definition (see memory-barrier.txt) read barriers orders
reads vs reads and write barriers orders writes agains writes.
but neither of these orders reads vs. writes.

That means we can implement smp_wmb,smp_rmb,wmb and rmb as
simple compiler barriers. To avoid reviewing all driver code
for correct barrier usage we keep dma_[rw]mb as serialization
for now.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2015-10-14 14:32:01 +02:00
..
appldata s390: appldata: drop owner assignment from platform_drivers 2014-10-20 16:20:13 +02:00
boot s390/boot/decompression: disable floating point in decompressor 2015-09-29 14:45:10 +02:00
configs s390/defconfig: set SCSI_DH=y 2015-10-01 10:48:36 +02:00
crypto s390/crypto: add cpu feature modaliases for crypto modules 2015-07-22 09:58:02 +02:00
hypfs Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-07-04 19:36:06 -07:00
include s390/barrier: avoid serialization in [smp_]rmb and [smp_]wmb 2015-10-14 14:32:01 +02:00
kernel s390/vdso: use correct memory barrier 2015-10-14 14:32:01 +02:00
kvm KVM: s390: Replace incorrect atomic_or with atomic_andnot 2015-09-16 17:01:06 +02:00
lib s390/spinlock: use correct barriers 2015-10-14 14:32:00 +02:00
mm libnvdimm for 4.3: 2015-09-08 14:35:59 -07:00
net bpf: s390: Fix build error caused by the struct bpf_array member name changed 2015-08-11 11:49:40 -07:00
numa s390/numa: write kernel message when emu_size has been increased 2015-10-14 14:31:59 +02:00
oprofile s390/oprofile: fix compile error 2015-07-01 09:34:39 +02:00
pci dma-mapping: consolidate dma_set_mask 2015-09-10 13:29:01 -07:00
Kbuild s390/numa: add core infrastructure 2015-08-03 18:40:25 +02:00
Kconfig kexec: split kexec_load syscall from kexec core code 2015-09-10 13:29:01 -07:00
Kconfig.debug Kconfig: consolidate CONFIG_DEBUG_STRICT_USER_COPY_CHECKS 2013-04-30 17:04:09 -07:00
Makefile s390/sclp: convert early sclp console code to C 2015-07-29 09:11:39 +02:00
defconfig s390: new default configuration 2015-06-25 09:39:25 +02:00