MIPS: cmpxchg64() and HAVE_VIRT_CPU_ACCOUNTING_GEN don't work for 32-bit SMP

__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@decadent.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Deng-Cheng Zhu <dengcheng.zhu@mips.com>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # 4.1+
Patchwork: https://patchwork.linux-mips.org/patch/17413/
Signed-off-by: James Hogan <jhogan@kernel.org>

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 43411118dd4f8d1cab9b893d067df9178be3fab6..b09b644cd57c563309be27c30ef792f110400724 100644 (file)
--- 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 903f3bf48419cb917dfc15af9013674e45c23017..ae2b4583b486417d0cff8aef6ba064a9e9709f2b 100644 (file)
--- 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