linux-kernel - [PATCH 4.14 023/193] MIPS: cmpxchg64() and HAVE_VIRT_CPU_ACCOUNTING

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Date:   Tue, 28 Nov 2017 11:24:30 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ben Hutchings <ben@...adent.org.uk>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Deng-Cheng Zhu <dengcheng.zhu@...s.com>,
        linux-mips@...ux-mips.org, James Hogan <jhogan@...nel.org>
Subject: [PATCH 4.14 023/193] MIPS: cmpxchg64() and HAVE_VIRT_CPU_ACCOUNTING_GEN dont work for 32-bit SMP

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Hutchings <ben@...adent.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@...adent.org.uk>
Cc: Ralf Baechle <ralf@...ux-mips.org>
Cc: Deng-Cheng Zhu <dengcheng.zhu@...s.com>
Cc: linux-mips@...ux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/17413/
Signed-off-by: James Hogan <jhogan@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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