https://github.com/torvalds/linux
Revision 720dc7ab252bbdf404cab7b909e26b31e602bf7e authored by Huacai Chen on 25 August 2022, 11:34:59 UTC, committed by Huacai Chen on 25 August 2022, 11:34:59 UTC
LoongArch only support 32-bit/64-bit xchg/cmpxchg in native. But percpu operation, qspinlock and some drivers need 8-bit/16-bit xchg/cmpxchg. We add subword xchg/cmpxchg emulation in this patch because the emulation has better performance than the generic implementation (on NUMA system), and it can fix some build errors meanwhile [1]. LoongArch's guarantee for forward progress (avoid many ll/sc happening at the same time and no one succeeds): We have the "exclusive access (with timeout) of ll" feature to avoid simultaneous ll (which also blocks other memory load/store on the same address), and the "random delay of sc" feature to avoid simultaneous sc. It is a mandatory requirement for multi-core LoongArch processors to implement such features, only except those single-core and dual-core processors (they also don't support multi-chip interconnection). Feature bits are introduced in CPUCFG3, bit 3 and bit 4 [2]. [1] https://lore.kernel.org/loongarch/CAAhV-H6vvkuOzy8OemWdYK3taj5Jn3bFX0ZTwE=twM8ywpBUYA@mail.gmail.com/T/#t [2] https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#_cpucfg Reported-by: Sudip Mukherjee (Codethink) <sudipm.mukherjee@gmail.com> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Rui Wang <wangrui@loongson.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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Tip revision: 720dc7ab252bbdf404cab7b909e26b31e602bf7e authored by Huacai Chen on 25 August 2022, 11:34:59 UTC
LoongArch: Add subword xchg/cmpxchg emulation
LoongArch: Add subword xchg/cmpxchg emulation
Tip revision: 720dc7a
File | Mode | Size |
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Documentation | ||
LICENSES | ||
arch | ||
block | ||
certs | ||
crypto | ||
drivers | ||
fs | ||
include | ||
init | ||
io_uring | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.clang-format | -rw-r--r-- | 19.9 KB |
.cocciconfig | -rw-r--r-- | 59 bytes |
.get_maintainer.ignore | -rw-r--r-- | 71 bytes |
.gitattributes | -rw-r--r-- | 62 bytes |
.gitignore | -rw-r--r-- | 1.9 KB |
.mailmap | -rw-r--r-- | 23.5 KB |
COPYING | -rw-r--r-- | 496 bytes |
CREDITS | -rw-r--r-- | 99.1 KB |
Kbuild | -rw-r--r-- | 1.3 KB |
Kconfig | -rw-r--r-- | 555 bytes |
MAINTAINERS | -rw-r--r-- | 663.5 KB |
Makefile | -rw-r--r-- | 64.5 KB |
README | -rw-r--r-- | 727 bytes |
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