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cbnz/tbnz don't update the condition flags, so remove the "cc" clobbers
from inline asm blocks that only use these instructions to implement
conditional branches.
(cherry picked from commit 95c4189689f92fba7ecf9097173404d4928c6e9b)
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Linux requires a number of atomic operations to provide full barrier
semantics, that is no memory accesses after the operation can be
observed before any accesses up to and including the operation in
program order.
On arm64, these operations have been incorrectly implemented as follows:
// A, B, C are independent memory locations
<Access [A]>
// atomic_op (B)
1: ldaxr x0, [B] // Exclusive load with acquire
<op(B)>
stlxr w1, x0, [B] // Exclusive store with release
cbnz w1, 1b
<Access [C]>
The assumption here being that two half barriers are equivalent to a
full barrier, so the only permitted ordering would be A -> B -> C
(where B is the atomic operation involving both a load and a store).
This patch implements this solution for our barriered atomic operations,
ensuring that we satisfy the full barrier requirements where they are
needed.
(cherry picked from commit 8e86f0b409a44193f1587e87b69c5dcf8f65be67)
Cc: <stable@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Make sure the value we are going to return is referenced in order to
avoid warnings from newer GCCs such as:
arch/arm64/include/asm/cmpxchg.h:162:3: warning: value computed is not used [-Wunused-value]
((__typeof__(*(ptr)))__cmpxchg_mb((ptr), \
^
net/netfilter/nf_conntrack_core.c:674:2: note: in expansion of macro ‘cmpxchg’
cmpxchg(&nf_conntrack_hash_rnd, 0, rand);
[Modified to use the current underlying implementation as current
mainline for both cmpxchg() and cmpxchg_local() does -- broonie]
(cherry picked from commit 60010e508111b2fd3d73de56f3b2c2bfc0f9eba1)
Signed-off-by: Mark Hambleton <mahamble@broadcom.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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This patch introduces cmpxchg64_relaxed for arm64 using the existing
cmpxchg_local macro, which performs a cmpxchg operation (up to 64 bits)
without barrier semantics.
(cherry picked from commit cf10b79a7d88edc689479af989b3a88e9adf07ff)
Change-Id: Ia5da0af964dac47203c18d276c92aa5fee218307
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Drivers use cmpxchg64, cmpxchg64_local to perform 64-bit operation, so
they can cross 32-bit and 64-bit platforms (it is a standard way).
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Our uses of inline asm constraints for atomic operations are fairly
wild and varied. We basically need to guarantee the following:
1. Any instructions with barrier implications
(load-acquire/store-release) have a "memory" clobber
2. When performing exclusive accesses, the addresing mode is generated
using the "Q" constraint
3. Atomic blocks which use the condition flags, have a "cc" clobber
This patch addresses these concerns which, as well as fixing the
semantics of the code, stops GCC complaining about impossible asm
constraints.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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This patch introduces a few AArch64-specific header files together with
Kbuild entries for generic headers.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
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