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@ -561,7 +561,6 @@ struct signalfd_siginfo |
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#define ECB_C99 (__STDC_VERSION__ >= 199901L) |
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#define ECB_C11 (__STDC_VERSION__ >= 201112L) |
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#define ECB_CPP (__cplusplus+0) |
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#define ECB_CPP98 (__cplusplus >= 199711L) |
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#define ECB_CPP11 (__cplusplus >= 201103L) |
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/*****************************************************************************/ |
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@ -616,10 +615,10 @@ struct signalfd_siginfo |
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#ifndef ECB_MEMORY_FENCE |
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#if ECB_GCC_VERSION(4,7) |
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/* see comment below about the C11 memory model. in short - avoid */ |
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/* see comment below (stdatomic.h) about the C11 memory model. */ |
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#define ECB_MEMORY_FENCE __atomic_thread_fence (__ATOMIC_SEQ_CST) |
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#elif defined __clang && __has_feature (cxx_atomic) |
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/* see above */ |
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/* see comment below (stdatomic.h) about the C11 memory model. */ |
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#define ECB_MEMORY_FENCE __c11_atomic_thread_fence (__ATOMIC_SEQ_CST) |
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#elif ECB_GCC_VERSION(4,4) || defined __INTEL_COMPILER || defined __clang__ |
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#define ECB_MEMORY_FENCE __sync_synchronize () |
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@ -646,8 +645,12 @@ struct signalfd_siginfo |
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/* we assume that these memory fences work on all variables/all memory accesses, */ |
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/* not just C11 atomics and atomic accesses */ |
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#include <stdatomic.h> |
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/* unfortunately, the C11 memory model seems to be very limited, and unable to express */ |
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/* simple barrier semantics. That means we need to take out thor's hammer. */ |
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/* Unfortunately, neither gcc 4.7 nor clang 3.1 generate any instructions for */ |
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/* any fence other than seq_cst, which isn't very efficient for us. */ |
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/* Why that is, we don't know - either the C11 memory model is quite useless */ |
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/* for most usages, or gcc and clang have a bug */ |
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/* I *currently* lean towards the latter, and inefficiently implement */ |
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/* all three of ecb's fences as a seq_cst fence */ |
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#define ECB_MEMORY_FENCE atomic_thread_fence (memory_order_seq_cst) |
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#endif |
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#endif |
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@ -3137,7 +3140,7 @@ ev_run (EV_P_ int flags) |
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pipe_write_wanted = 0; /* just an optimisation, no fence needed */ |
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MEMORY_FENCE_ACQUIRE; |
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ECB_MEMORY_FENCE_ACQUIRE; |
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if (pipe_write_skipped) |
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{ |
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assert (("libev: pipe_w not active, but pipe not written", ev_is_active (&pipe_w))); |
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Marc Alexander Lehmann
8 years ago