From: Will Deacon <will@kernel.org>
To: linux-kernel@vger.kernel.org
Cc: linux-arch@vger.kernel.org, kernel-team@android.com,
Will Deacon <will@kernel.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Peter Zijlstra <peterz@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Segher Boessenkool <segher@kernel.crashing.org>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
Arnd Bergmann <arnd@arndb.de>,
Peter Oberparleiter <oberpar@linux.ibm.com>,
Masahiro Yamada <masahiroy@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>
Subject: [PATCH v2 07/10] locking/barriers: Use '__unqual_scalar_typeof' for load-acquire macros
Date: Thu, 23 Jan 2020 15:33:38 +0000 [thread overview]
Message-ID: <20200123153341.19947-8-will@kernel.org> (raw)
In-Reply-To: <20200123153341.19947-1-will@kernel.org>
Passing volatile-qualified pointers to the asm-generic implementations of
the load-acquire macros results in a re-load from the stack due to the
temporary result variable inheriting the volatile semantics thanks to the
use of 'typeof()'.
Define these temporary variables using 'unqual_scalar_typeof' to drop
the volatile qualifier in the case that they are scalar types.
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Will Deacon <will@kernel.org>
---
include/asm-generic/barrier.h | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
index 85b28eb80b11..2eacaf7d62f6 100644
--- a/include/asm-generic/barrier.h
+++ b/include/asm-generic/barrier.h
@@ -128,10 +128,10 @@ do { \
#ifndef __smp_load_acquire
#define __smp_load_acquire(p) \
({ \
- typeof(*p) ___p1 = READ_ONCE(*p); \
+ __unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
__smp_mb(); \
- ___p1; \
+ (typeof(*p))___p1; \
})
#endif
@@ -183,10 +183,10 @@ do { \
#ifndef smp_load_acquire
#define smp_load_acquire(p) \
({ \
- typeof(*p) ___p1 = READ_ONCE(*p); \
+ __unqual_scalar_typeof(*p) ___p1 = READ_ONCE(*p); \
compiletime_assert_atomic_type(*p); \
barrier(); \
- ___p1; \
+ (typeof(*p))___p1; \
})
#endif
@@ -229,14 +229,14 @@ do { \
#ifndef smp_cond_load_relaxed
#define smp_cond_load_relaxed(ptr, cond_expr) ({ \
typeof(ptr) __PTR = (ptr); \
- typeof(*ptr) VAL; \
+ __unqual_scalar_typeof(*ptr) VAL; \
for (;;) { \
VAL = READ_ONCE(*__PTR); \
if (cond_expr) \
break; \
cpu_relax(); \
} \
- VAL; \
+ (typeof(*ptr))VAL; \
})
#endif
@@ -250,10 +250,10 @@ do { \
*/
#ifndef smp_cond_load_acquire
#define smp_cond_load_acquire(ptr, cond_expr) ({ \
- typeof(*ptr) _val; \
+ __unqual_scalar_typeof(*ptr) _val; \
_val = smp_cond_load_relaxed(ptr, cond_expr); \
smp_acquire__after_ctrl_dep(); \
- _val; \
+ (typeof(*ptr))_val; \
})
#endif
--
2.25.0.341.g760bfbb309-goog
next prev parent reply other threads:[~2020-01-23 15:34 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-23 15:33 [PATCH v2 00/10] Rework READ_ONCE() to improve codegen Will Deacon
2020-01-23 15:33 ` [PATCH v2 01/10] compiler/gcc: Emit build-time warning for GCC prior to version 4.8 Will Deacon
2020-01-23 15:33 ` [PATCH v2 02/10] netfilter: Avoid assigning 'const' pointer to non-const pointer Will Deacon
2020-01-23 19:07 ` Nick Desaulniers
2020-01-24 8:24 ` Peter Zijlstra
2020-01-24 17:20 ` Nick Desaulniers
2020-01-27 12:04 ` David Laight
2020-01-24 17:36 ` Linus Torvalds
2020-01-24 22:00 ` Peter Zijlstra
2020-01-27 12:21 ` David Laight
2020-01-23 15:33 ` [PATCH v2 03/10] fault_inject: Don't rely on "return value" from WRITE_ONCE() Will Deacon
2020-01-23 15:33 ` [PATCH v2 04/10] READ_ONCE: Simplify implementations of {READ,WRITE}_ONCE() Will Deacon
2020-01-23 15:33 ` [PATCH v2 05/10] READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses Will Deacon
2020-01-25 8:27 ` Peter Zijlstra
2020-01-29 10:49 ` Peter Zijlstra
2020-01-23 15:33 ` [PATCH v2 06/10] READ_ONCE: Drop pointer qualifiers when reading from scalar types Will Deacon
2020-01-23 15:33 ` Will Deacon [this message]
2020-01-23 15:33 ` [PATCH v2 08/10] arm64: barrier: Use '__unqual_scalar_typeof' for acquire/release macros Will Deacon
2020-01-23 15:33 ` [PATCH v2 09/10] compiler/gcc: Raise minimum GCC version for kernel builds to 4.8 Will Deacon
2020-01-23 18:36 ` Nick Desaulniers
2020-01-24 8:26 ` Peter Zijlstra
2020-01-24 17:05 ` Nick Desaulniers
2020-01-24 23:29 ` Peter Zijlstra
2020-01-25 10:34 ` Michael Ellerman
2020-01-23 15:33 ` [PATCH v2 10/10] gcov: Remove old GCC 3.4 support Will Deacon
2020-01-23 18:51 ` Nick Desaulniers
2020-01-28 14:56 ` Peter Oberparleiter
2020-01-23 17:07 ` [PATCH v2 00/10] Rework READ_ONCE() to improve codegen David Laight
2020-01-23 17:16 ` Will Deacon
2020-01-23 17:32 ` David Laight
2020-01-23 18:45 ` Nick Desaulniers
2020-01-23 19:01 ` Arvind Sankar
2020-01-24 10:11 ` David Laight
2020-01-26 1:10 ` Qais Yousef
2020-01-27 7:26 ` Arnd Bergmann
2020-01-23 17:59 ` Linus Torvalds
2020-01-24 8:33 ` Peter Zijlstra
2020-01-24 10:41 ` Peter Zijlstra
2020-02-10 9:50 ` Masahiro Yamada
2020-02-10 9:59 ` Will Deacon
2020-01-31 10:20 ` David Howells
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