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>,
Mark Rutland <mark.rutland@arm.com>
Subject: [RFC PATCH 8/8] arm64: barrier: Use '__unqual_scalar_typeof' for acquire/release macros
Date: Fri, 10 Jan 2020 16:56:36 +0000 [thread overview]
Message-ID: <20200110165636.28035-9-will@kernel.org> (raw)
In-Reply-To: <20200110165636.28035-1-will@kernel.org>
Passing volatile-qualified pointers to the arm64 implementations of the
load-acquire/store-release macros results in a re-load from the stack
and a bunch of associated stack-protector churn 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: Mark Rutland <mark.rutland@arm.com>
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>
---
arch/arm64/include/asm/barrier.h | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index 7d9cc5ec4971..fb4c27506ef4 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -76,8 +76,8 @@ static inline unsigned long array_index_mask_nospec(unsigned long idx,
#define __smp_store_release(p, v) \
do { \
typeof(p) __p = (p); \
- union { typeof(*p) __val; char __c[1]; } __u = \
- { .__val = (__force typeof(*p)) (v) }; \
+ union { __unqual_scalar_typeof(*p) __val; char __c[1]; } __u = \
+ { .__val = (__force __unqual_scalar_typeof(*p)) (v) }; \
compiletime_assert_atomic_type(*p); \
kasan_check_write(__p, sizeof(*p)); \
switch (sizeof(*p)) { \
@@ -110,7 +110,7 @@ do { \
#define __smp_load_acquire(p) \
({ \
- union { typeof(*p) __val; char __c[1]; } __u; \
+ union { __unqual_scalar_typeof(*p) __val; char __c[1]; } __u; \
typeof(p) __p = (p); \
compiletime_assert_atomic_type(*p); \
kasan_check_read(__p, sizeof(*p)); \
@@ -136,33 +136,33 @@ do { \
: "Q" (*__p) : "memory"); \
break; \
} \
- __u.__val; \
+ (typeof(*p))__u.__val; \
})
#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; \
__cmpwait_relaxed(__PTR, VAL); \
} \
- VAL; \
+ (typeof(*ptr))VAL; \
})
#define smp_cond_load_acquire(ptr, cond_expr) \
({ \
typeof(ptr) __PTR = (ptr); \
- typeof(*ptr) VAL; \
+ __unqual_scalar_typeof(*ptr) VAL; \
for (;;) { \
VAL = smp_load_acquire(__PTR); \
if (cond_expr) \
break; \
__cmpwait_relaxed(__PTR, VAL); \
} \
- VAL; \
+ (typeof(*ptr))VAL; \
})
#include <asm-generic/barrier.h>
--
2.25.0.rc1.283.g88dfdc4193-goog
next prev parent reply other threads:[~2020-01-10 16:57 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-10 16:56 [RFC PATCH 0/8] Rework READ_ONCE() to improve codegen Will Deacon
2020-01-10 16:56 ` [RFC PATCH 1/8] compiler/gcc: Emit build-time warning for GCC prior to version 4.8 Will Deacon
2020-01-10 17:35 ` Arnd Bergmann
2020-01-10 17:53 ` Joe Perches
2020-01-13 14:39 ` Arnd Bergmann
2020-01-13 15:35 ` Masahiro Yamada
2020-01-13 14:27 ` Will Deacon
2020-01-14 21:39 ` Nick Desaulniers
2020-01-15 10:35 ` David Laight
2020-01-15 10:49 ` Arnd Bergmann
2020-01-10 16:56 ` [RFC PATCH 2/8] netfilter: Avoid assigning 'const' pointer to non-const pointer Will Deacon
2020-01-10 16:56 ` [RFC PATCH 3/8] fault_inject: Don't rely on "return value" from WRITE_ONCE() Will Deacon
2020-01-10 16:56 ` [RFC PATCH 4/8] READ_ONCE: Simplify implementations of {READ,WRITE}_ONCE() Will Deacon
2020-01-10 16:56 ` [RFC PATCH 5/8] READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses Will Deacon
2020-01-10 19:24 ` Arnd Bergmann
2020-01-13 16:16 ` Will Deacon
2020-01-10 16:56 ` [RFC PATCH 6/8] READ_ONCE: Drop pointer qualifiers when reading from scalar types Will Deacon
2020-01-10 18:54 ` Linus Torvalds
2020-01-13 14:59 ` Will Deacon
2020-01-13 17:42 ` Luc Van Oostenryck
2020-01-13 19:31 ` Linus Torvalds
2020-01-10 16:56 ` [RFC PATCH 7/8] locking/barriers: Use '__unqual_scalar_typeof' for load-acquire macros Will Deacon
2020-01-10 19:42 ` Arnd Bergmann
2020-01-13 15:01 ` Will Deacon
2020-01-10 16:56 ` Will Deacon [this message]
2020-01-10 17:45 ` [RFC PATCH 8/8] arm64: barrier: Use '__unqual_scalar_typeof' for acquire/release macros Mark Rutland
2020-01-10 17:58 ` [RFC PATCH 0/8] Rework READ_ONCE() to improve codegen Arnd Bergmann
2020-01-10 19:46 ` Arnd Bergmann
2020-01-10 20:14 ` Linus Torvalds
2020-01-13 13:03 ` Arnd Bergmann
2020-01-13 11:20 ` David Laight
2020-01-13 12:40 ` Christian Borntraeger
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200110165636.28035-9-will@kernel.org \
--to=will@kernel.org \
--cc=arnd@arndb.de \
--cc=borntraeger@de.ibm.com \
--cc=kernel-team@android.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luc.vanoostenryck@gmail.com \
--cc=mark.rutland@arm.com \
--cc=mpe@ellerman.id.au \
--cc=peterz@infradead.org \
--cc=segher@kernel.crashing.org \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).