This is a note to let you know that I've just added the patch titled

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

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: mips-cmpxchg64-and-have_virt_cpu_accounting_gen-don-t-work-for-32-bit-smp.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From a3f143106596d739e7fbc4b84c96b1475247d876 Mon Sep 17 00:00:00 2001

From: Ben Hutchings ben@decadent.org.uk Date: Wed, 4 Oct 2017 03:46:14 +0100 Subject: MIPS: cmpxchg64() and HAVE_VIRT_CPU_ACCOUNTING_GEN don't work for 32-bit SMP

From: Ben Hutchings ben@decadent.org.uk

commit a3f143106596d739e7fbc4b84c96b1475247d876 upstream.

__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 Patchwork: https://patchwork.linux-mips.org/patch/17413/ Signed-off-by: James Hogan jhogan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/mips/Kconfig | 2 +- arch/mips/include/asm/cmpxchg.h | 2 ++ 2 files changed, 3 insertions(+), 1 deletion(-)

--- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -65,7 +65,7 @@ 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 --- a/arch/mips/include/asm/cmpxchg.h +++ b/arch/mips/include/asm/cmpxchg.h @@ -204,8 +204,10 @@ static inline unsigned long __cmpxchg(vo #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

Patches currently in stable-queue which might be from ben@decadent.org.uk are

queue-4.14/mips-cmpxchg64-and-have_virt_cpu_accounting_gen-don-t-work-for-32-bit-smp.patch