Add generic support for try_cmpxchg64{,_acquire,_release,_relaxed}
and their falbacks involving cmpxchg64.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220515184205.103089-2-ubizjak@gmail.com
Arnd reports that on 32-bit architectures, the fallbacks for
atomic64_read_acquire() and atomic64_set_release() are broken as they
use smp_load_acquire() and smp_store_release() respectively, which do
not work on types larger than the native word size.
Since those contain compiletime_assert_atomic_type(), any attempt to use
those fallbacks will result in a build-time error. e.g. with the
following added to arch/arm/kernel/setup.c:
| void test_atomic64(atomic64_t *v)
| {
| atomic64_set_release(v, 5);
| atomic64_read_acquire(v);
| }
The compiler will complain as follows:
| In file included from <command-line>:
| In function 'arch_atomic64_set_release',
| inlined from 'test_atomic64' at ./include/linux/atomic/atomic-instrumented.h:669:2:
| ././include/linux/compiler_types.h:346:38: error: call to '__compiletime_assert_9' declared with attribute error: Need native word sized stores/loads for atomicity.
| 346 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| | ^
| ././include/linux/compiler_types.h:327:4: note: in definition of macro '__compiletime_assert'
| 327 | prefix ## suffix(); \
| | ^~~~~~
| ././include/linux/compiler_types.h:346:2: note: in expansion of macro '_compiletime_assert'
| 346 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| | ^~~~~~~~~~~~~~~~~~~
| ././include/linux/compiler_types.h:349:2: note: in expansion of macro 'compiletime_assert'
| 349 | compiletime_assert(__native_word(t), \
| | ^~~~~~~~~~~~~~~~~~
| ./include/asm-generic/barrier.h:133:2: note: in expansion of macro 'compiletime_assert_atomic_type'
| 133 | compiletime_assert_atomic_type(*p); \
| | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| ./include/asm-generic/barrier.h:164:55: note: in expansion of macro '__smp_store_release'
| 164 | #define smp_store_release(p, v) do { kcsan_release(); __smp_store_release(p, v); } while (0)
| | ^~~~~~~~~~~~~~~~~~~
| ./include/linux/atomic/atomic-arch-fallback.h:1270:2: note: in expansion of macro 'smp_store_release'
| 1270 | smp_store_release(&(v)->counter, i);
| | ^~~~~~~~~~~~~~~~~
| make[2]: *** [scripts/Makefile.build:288: arch/arm/kernel/setup.o] Error 1
| make[1]: *** [scripts/Makefile.build:550: arch/arm/kernel] Error 2
| make: *** [Makefile:1831: arch/arm] Error 2
Fix this by only using smp_load_acquire() and smp_store_release() for
native atomic types, and otherwise falling back to the regular barriers
necessary for acquire/release semantics, as we do in the more generic
acquire and release fallbacks.
Since the fallback templates are used to generate the atomic64_*() and
atomic_*() operations, the __native_word() check is added to both. For
the atomic_*() operations, which are always 32-bit, the __native_word()
check is redundant but not harmful, as it is always true.
For the example above this works as expected on 32-bit, e.g. for arm
multi_v7_defconfig:
| <test_atomic64>:
| push {r4, r5}
| dmb ish
| pldw [r0]
| mov r2, #5
| mov r3, #0
| ldrexd r4, [r0]
| strexd r4, r2, [r0]
| teq r4, #0
| bne 484 <test_atomic64+0x14>
| ldrexd r2, [r0]
| dmb ish
| pop {r4, r5}
| bx lr
... and also on 64-bit, e.g. for arm64 defconfig:
| <test_atomic64>:
| bti c
| paciasp
| mov x1, #0x5
| stlr x1, [x0]
| ldar x0, [x0]
| autiasp
| ret
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20220207101943.439825-1-mark.rutland@arm.com
Adds the required KCSAN instrumentation for barriers of atomics.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Now that all architectures provide arch_{atomic,atomic64}_*(), we can
build arch_atomic_long_*() atop these, which can be safely used in
noinstr code. The regular atomic_long_*() wrappers are built atop these,
as we do for {atomic,atomic64}_*() atop arch_{atomic,atomic64}_*().
We don't provide arch_* versions of the cond_read*() variants, as we
don't have arch_* versions of the underlying atomic/atomic64 functions
(nor the smp_cond_load*() helpers these are typically based on).
Note that the headers in this patch under include/linux/atomic/ are
generated by the scripts in scripts/atomic/.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210713105253.7615-5-mark.rutland@arm.com
The generated atomic headers are only intended to be included directly
by <linux/atomic.h>, but are spread across include/linux/ and
include/asm-generic/, where people mnay be encouraged to include them.
This patch centralizes them under include/linux/atomic/.
Other than the header guards and hashes, there is no change to any of
the generated headers as a result of this patch.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210713105253.7615-4-mark.rutland@arm.com
Uros Bizjak
Mark Rutland
Marco Elver