Re: Patch "asm-generic/bitops/lock.h: Rewrite using atomic_fetch_" causes kernel crash
From: Peter Zijlstra <peterz@infradead.org>
Date: 2018-08-30 14:46:25
Also in:
linux-arm-kernel, lkml
Subsystem:
atomic infrastructure, synopsys arc architecture, the rest · Maintainers:
Will Deacon, Peter Zijlstra, Boqun Feng, Vineet Gupta, Linus Torvalds
On Thu, Aug 30, 2018 at 04:29:20PM +0200, Peter Zijlstra wrote:
Also, once it all works, they should look at switching to _relaxed atomics for LL/SC.
A little something like so.. should save a few smp_mb(). ---
diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h
index 4e0072730241..714b54c308b0 100644
--- a/arch/arc/include/asm/atomic.h
+++ b/arch/arc/include/asm/atomic.h@@ -44,7 +44,7 @@ static inline void atomic_##op(int i, atomic_t *v) \ } \ #define ATOMIC_OP_RETURN(op, c_op, asm_op) \ -static inline int atomic_##op##_return(int i, atomic_t *v) \ +static inline int atomic_##op##_return_relaxed(int i, atomic_t *v) \ { \ unsigned int val; \ \
@@ -69,8 +69,11 @@ static inline int atomic_##op##_return(int i, atomic_t *v) \ return val; \ } +#define atomic_add_return_relaxed atomic_add_return_relaxed +#define atomic_sub_return_relaxed atomic_sub_return_relaxed + #define ATOMIC_FETCH_OP(op, c_op, asm_op) \ -static inline int atomic_fetch_##op(int i, atomic_t *v) \ +static inline int atomic_fetch_##op##_relaxed(int i, atomic_t *v) \ { \ unsigned int val, orig; \ \
@@ -96,6 +99,14 @@ static inline int atomic_fetch_##op(int i, atomic_t *v) \ return orig; \ } +#define atomic_fetch_add_relaxed atomic_fetch_add_relaxed +#define atomic_fetch_sub_relaxed atomic_fetch_sub_relaxed + +#define atomic_fetch_and_relaxed atomic_fetch_and_relaxed +#define atomic_fetch_andnot_relaxed atomic_fetch_andnot_relaxed +#define atomic_fetch_or_relaxed atomic_fetch_or_relaxed +#define atomic_fetch_xor_relaxed atomic_fetch_xor_relaxed + #else /* !CONFIG_ARC_HAS_LLSC */ #ifndef CONFIG_SMP
@@ -379,7 +390,7 @@ static inline void atomic64_##op(long long a, atomic64_t *v) \ } \ #define ATOMIC64_OP_RETURN(op, op1, op2) \ -static inline long long atomic64_##op##_return(long long a, atomic64_t *v) \ +static inline long long atomic64_##op##_return_relaxed(long long a, atomic64_t *v) \ { \ unsigned long long val; \ \
@@ -401,8 +412,11 @@ static inline long long atomic64_##op##_return(long long a, atomic64_t *v) \ return val; \ } +#define atomic64_add_return_relaxed atomic64_add_return_relaxed +#define atomic64_sub_return_relaxed atomic64_sub_return_relaxed + #define ATOMIC64_FETCH_OP(op, op1, op2) \ -static inline long long atomic64_fetch_##op(long long a, atomic64_t *v) \ +static inline long long atomic64_fetch_##op##_relaxed(long long a, atomic64_t *v) \ { \ unsigned long long val, orig; \ \
@@ -424,6 +438,14 @@ static inline long long atomic64_fetch_##op(long long a, atomic64_t *v) \ return orig; \ } +#define atomic64_fetch_add_relaxed atomic64_fetch_add_relaxed +#define atomic64_fetch_sub_relaxed atomic64_fetch_sub_relaxed + +#define atomic64_fetch_and_relaxed atomic64_fetch_and_relaxed +#define atomic64_fetch_andnot_relaxed atomic64_fetch_andnot_relaxed +#define atomic64_fetch_or_relaxed atomic64_fetch_or_relaxed +#define atomic64_fetch_xor_relaxed atomic64_fetch_xor_relaxed + #define ATOMIC64_OPS(op, op1, op2) \ ATOMIC64_OP(op, op1, op2) \ ATOMIC64_OP_RETURN(op, op1, op2) \
@@ -434,6 +456,12 @@ static inline long long atomic64_fetch_##op(long long a, atomic64_t *v) \ ATOMIC64_OPS(add, add.f, adc) ATOMIC64_OPS(sub, sub.f, sbc) + +#undef ATOMIC64_OPS +#define ATOMIC64_OPS(op, op1, op2) \ + ATOMIC64_OP(op, op1, op2) \ + ATOMIC64_FETCH_OP(op, op1, op2) + ATOMIC64_OPS(and, and, and) ATOMIC64_OPS(andnot, bic, bic) ATOMIC64_OPS(or, or, or)