diff options
| author | Will Deacon <will.deacon@arm.com> | 2018-09-13 14:28:33 +0100 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2018-12-07 17:28:01 +0000 |
| commit | b4f9209bfcd5964551de434342818334ab9c8c7e (patch) | |
| tree | 69578d6a718bb6f9ff0f3f4cad3cecb801a88758 /arch | |
| parent | 5ef3fe4cecdf82fdd71ce78988403963d01444d4 (diff) | |
arm64: Avoid masking "old" for LSE cmpxchg() implementation
The CAS instructions implicitly access only the relevant bits of the "old"
argument, so there is no need for explicit masking via type-casting as
there is in the LL/SC implementation.
Move the casting into the LL/SC code and remove it altogether for the LSE
implementation.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/include/asm/atomic_ll_sc.h | 8 | ||||
| -rw-r--r-- | arch/arm64/include/asm/atomic_lse.h | 4 | ||||
| -rw-r--r-- | arch/arm64/include/asm/cmpxchg.h | 4 |
3 files changed, 12 insertions, 4 deletions
diff --git a/arch/arm64/include/asm/atomic_ll_sc.h b/arch/arm64/include/asm/atomic_ll_sc.h index f02d3bf7b9e6..b53f70dd6e10 100644 --- a/arch/arm64/include/asm/atomic_ll_sc.h +++ b/arch/arm64/include/asm/atomic_ll_sc.h @@ -257,6 +257,14 @@ __LL_SC_PREFIX(__cmpxchg_case_##name##sz(volatile void *ptr, \ unsigned long tmp; \ u##sz oldval; \ \ + /* \ + * Sub-word sizes require explicit casting so that the compare \ + * part of the cmpxchg doesn't end up interpreting non-zero \ + * upper bits of the register containing "old". \ + */ \ + if (sz < 32) \ + old = (u##sz)old; \ + \ asm volatile( \ " prfm pstl1strm, %[v]\n" \ "1: ld" #acq "xr" #sfx "\t%" #w "[oldval], %[v]\n" \ diff --git a/arch/arm64/include/asm/atomic_lse.h b/arch/arm64/include/asm/atomic_lse.h index 4d6f917b654e..a424355240c5 100644 --- a/arch/arm64/include/asm/atomic_lse.h +++ b/arch/arm64/include/asm/atomic_lse.h @@ -448,11 +448,11 @@ static inline long atomic64_dec_if_positive(atomic64_t *v) #define __CMPXCHG_CASE(w, sfx, name, sz, mb, cl...) \ static inline u##sz __cmpxchg_case_##name##sz(volatile void *ptr, \ - unsigned long old, \ + u##sz old, \ u##sz new) \ { \ register unsigned long x0 asm ("x0") = (unsigned long)ptr; \ - register unsigned long x1 asm ("x1") = old; \ + register u##sz x1 asm ("x1") = old; \ register u##sz x2 asm ("x2") = new; \ \ asm volatile(ARM64_LSE_ATOMIC_INSN( \ diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h index 1f0340fc6dad..3f9376f1c409 100644 --- a/arch/arm64/include/asm/cmpxchg.h +++ b/arch/arm64/include/asm/cmpxchg.h @@ -123,9 +123,9 @@ static inline unsigned long __cmpxchg##sfx(volatile void *ptr, \ { \ switch (size) { \ case 1: \ - return __cmpxchg_case##sfx##_8(ptr, (u8)old, new); \ + return __cmpxchg_case##sfx##_8(ptr, old, new); \ case 2: \ - return __cmpxchg_case##sfx##_16(ptr, (u16)old, new); \ + return __cmpxchg_case##sfx##_16(ptr, old, new); \ case 4: \ return __cmpxchg_case##sfx##_32(ptr, old, new); \ case 8: \ |