From 29f006fdefe6f88abde973a0b0f20d2704e93fd4 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Sat, 29 Aug 2020 22:03:35 +0900
Subject: asm-generic/atomic: Add try_cmpxchg() fallbacks

Only x86 provides try_cmpxchg() outside of the atomic_t interfaces,
provide generic fallbacks to create this interface from the widely
available cmpxchg() function.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/159870621515.1229682.15506193091065001742.stgit@devnote2
---
 scripts/atomic/gen-atomic-instrumented.sh | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

(limited to 'scripts/atomic/gen-atomic-instrumented.sh')

diff --git a/scripts/atomic/gen-atomic-instrumented.sh b/scripts/atomic/gen-atomic-instrumented.sh
index 6afadf73da17..85dc25685c0d 100755
--- a/scripts/atomic/gen-atomic-instrumented.sh
+++ b/scripts/atomic/gen-atomic-instrumented.sh
@@ -103,14 +103,31 @@ gen_xchg()
 	local xchg="$1"; shift
 	local mult="$1"; shift
 
+	if [ "${xchg%${xchg#try_cmpxchg}}" = "try_cmpxchg" ] ; then
+
+cat <<EOF
+#define ${xchg}(ptr, oldp, ...) \\
+({ \\
+	typeof(ptr) __ai_ptr = (ptr); \\
+	typeof(oldp) __ai_oldp = (oldp); \\
+	instrument_atomic_write(__ai_ptr, ${mult}sizeof(*__ai_ptr)); \\
+	instrument_atomic_write(__ai_oldp, ${mult}sizeof(*__ai_oldp)); \\
+	arch_${xchg}(__ai_ptr, __ai_oldp, __VA_ARGS__); \\
+})
+EOF
+
+	else
+
 cat <<EOF
-#define ${xchg}(ptr, ...)						\\
-({									\\
-	typeof(ptr) __ai_ptr = (ptr);					\\
-	instrument_atomic_write(__ai_ptr, ${mult}sizeof(*__ai_ptr));		\\
-	arch_${xchg}(__ai_ptr, __VA_ARGS__);				\\
+#define ${xchg}(ptr, ...) \\
+({ \\
+	typeof(ptr) __ai_ptr = (ptr); \\
+	instrument_atomic_write(__ai_ptr, ${mult}sizeof(*__ai_ptr)); \\
+	arch_${xchg}(__ai_ptr, __VA_ARGS__); \\
 })
 EOF
+
+	fi
 }
 
 gen_optional_xchg()
@@ -160,7 +177,7 @@ grep '^[a-z]' "$1" | while read name meta args; do
 	gen_proto "${meta}" "${name}" "atomic64" "s64" ${args}
 done
 
-for xchg in "xchg" "cmpxchg" "cmpxchg64"; do
+for xchg in "xchg" "cmpxchg" "cmpxchg64" "try_cmpxchg"; do
 	for order in "" "_acquire" "_release" "_relaxed"; do
 		gen_optional_xchg "${xchg}" "${order}"
 	done
-- 
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