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author | Ben Gamari <ben@smart-cactus.org> | 2023-02-13 13:13:05 -0500 |
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committer | Ben Gamari <ben@smart-cactus.org> | 2023-03-02 10:33:54 -0500 |
commit | 0a0e22f50550ab5ba2b789239cfdd7410662e120 (patch) | |
tree | a3a1448286a1f961a080b1a9f396a864a5a599a0 | |
parent | b73b70bfa976eb57f1c4ec0c0db97a5fab2bf9ff (diff) | |
download | haskell-0a0e22f50550ab5ba2b789239cfdd7410662e120.tar.gz |
rts: Statically assert alignment of Capability
In #22965 we noticed that changes in the size of `Capability` can result
in unsound behavior due to the `align` pragma claiming an alignment
which we don't in practice observe. Avoid this by statically asserting
that the size is a multiple of the alignment.
(cherry picked from commit 485ccddacff5ed8892348905754c02452ac8f523)
-rw-r--r-- | rts/Capability.h | 24 |
1 files changed, 16 insertions, 8 deletions
diff --git a/rts/Capability.h b/rts/Capability.h index 2910c3faf0..0c4848c08d 100644 --- a/rts/Capability.h +++ b/rts/Capability.h @@ -28,6 +28,16 @@ #include "BeginPrivate.h" +// We never want a Capability to overlap a cache line with +// anything else, so round it up to a cache line size: +#if defined(s390x_HOST_ARCH) +#define CAPABILITY_ALIGNMENT 256 +#elif !defined(mingw32_HOST_OS) +#define CAPABILITY_ALIGNMENT 64 +#else +#define CAPABILITY_ALIGNMENT 1 +#endif + /* N.B. This must be consistent with CapabilityPublic in RtsAPI.h */ struct Capability_ { // State required by the STG virtual machine when running Haskell @@ -169,14 +179,12 @@ struct Capability_ { StgTRecHeader *free_trec_headers; uint32_t transaction_tokens; } // typedef Capability is defined in RtsAPI.h - // We never want a Capability to overlap a cache line with anything - // else, so round it up to a cache line size: -#if defined(s390x_HOST_ARCH) - ATTRIBUTE_ALIGNED(256) -#elif !defined(mingw32_HOST_OS) - ATTRIBUTE_ALIGNED(64) -#endif - ; + ATTRIBUTE_ALIGNED(CAPABILITY_ALIGNMENT) +; + +// We allocate arrays of Capabilities therefore we must ensure that the size is +// a multiple of the claimed alignment +GHC_STATIC_ASSERT(sizeof(struct Capability_) % CAPABILITY_ALIGNMENT == 0, "Capability size does not match cache size"); #if defined(THREADED_RTS) #define ASSERT_TASK_ID(task) ASSERT(task->id == osThreadId()) |