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| author |   Paul E. McKenney <paulmck@kernel.org> | 2024-03-17 14:44:38 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2024-04-09 22:06:00 -0700 |
| commit | a88d970c8bb55dc20f319ce3e33c7ce0e9647480 (patch) | |
| tree | 3018a3725478213510ae0620aac3c54ca6996149 /lib/Makefile | |
| parent | parisc: add u16 support to cmpxchg() (diff) | |
| download | linux-a88d970c8bb55dc20f319ce3e33c7ce0e9647480.tar.xz linux-a88d970c8bb55dc20f319ce3e33c7ce0e9647480.zip | |
lib: Add one-byte emulation function
Architectures are required to provide four-byte cmpxchg() and 64-bit
architectures are additionally required to provide eight-byte cmpxchg().
However, there are cases where one-byte cmpxchg() would be extremely
useful. Therefore, provide cmpxchg_emu_u8() that emulates one-byte
cmpxchg() in terms of four-byte cmpxchg().
Note that this emulations is fully ordered, and can (for example) cause
one-byte cmpxchg_relaxed() to incur the overhead of full ordering.
If this causes problems for a given architecture, that architecture is
free to provide its own lighter-weight primitives.
[ paulmck: Apply Marco Elver feedback. ]
[ paulmck: Apply kernel test robot feedback. ]
[ paulmck: Drop two-byte support per Arnd Bergmann feedback. ]
Link: https://lore.kernel.org/all/0733eb10-5e7a-4450-9b8a-527b97c842ff@paulmck-laptop/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Marco Elver <elver@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: <linux-arch@vger.kernel.org>
Diffstat (limited to 'lib/Makefile')
| -rw-r--r-- | lib/Makefile | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/lib/Makefile b/lib/Makefile index ffc6b2341b45..cc3d52fdb477 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -236,6 +236,7 @@ obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o lib-$(CONFIG_GENERIC_BUG) += bug.o obj-$(CONFIG_HAVE_ARCH_TRACEHOOK) += syscall.o +obj-$(CONFIG_ARCH_NEED_CMPXCHG_1_EMU) += cmpxchg-emu.o obj-$(CONFIG_DYNAMIC_DEBUG_CORE) += dynamic_debug.o #ensure exported functions have prototypes |