__cmpxchg64_local_generic() is atomic only w.r.t tasks and interrupts
on the same CPU (that's what the 'local' means). We can't use it to
implement cmpxchg64() in SMP configurations.
So, for 32-bit SMP configurations:
- Don't define cmpxchg64()
- Don't enable HAVE_VIRT_CPU_ACCOUNTING_GEN, which requires it
Fixes: e2093c7b03c1 ("MIPS: Fall back to generic implementation of ...")
Fixes: bb877e96bea1 ("MIPS: Add support for full dynticks CPU time accounting")
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
arch/mips/Kconfig | 2 +-
arch/mips/include/asm/cmpxchg.h | 2 ++
2 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index cb7fcc4216fd..1e23f8455b7d 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -64,7 +64,7 @@ config MIPS
select HAVE_PERF_EVENTS
select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_SYSCALL_TRACEPOINTS
- select HAVE_VIRT_CPU_ACCOUNTING_GEN
+ select HAVE_VIRT_CPU_ACCOUNTING_GEN if 64BIT || !SMP
select IRQ_FORCED_THREADING
select MODULES_USE_ELF_RELA if MODULES && 64BIT
select MODULES_USE_ELF_REL if MODULES
diff --git a/arch/mips/include/asm/cmpxchg.h b/arch/mips/include/asm/cmpxchg.h
index 903f3bf48419..ae2b4583b486 100644
--- a/arch/mips/include/asm/cmpxchg.h
+++ b/arch/mips/include/asm/cmpxchg.h
@@ -202,8 +202,10 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
#else
#include <asm-generic/cmpxchg-local.h>
#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
+#ifndef CONFIG_SMP
#define cmpxchg64(ptr, o, n) cmpxchg64_local((ptr), (o), (n))
#endif
+#endif
#undef __scbeqz
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