memdb: compatible with Go 1.14's checkptr#14972
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sre-bot merged 4 commits intopingcap:masterfrom Feb 28, 2020
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## master #14972 +/- ##
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Hits ? 105619
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LGTM |
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LGTM Some of my personal projects might also be influenced by Go 1.14, I miss C so much... |
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/run-all-tests |
jackysp
approved these changes
Feb 27, 2020
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/merge |
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/run-all-tests |
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@bobotu merge failed. |
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/merge |
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Your auto merge job has been accepted, waiting for 14962 |
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/run-all-tests |
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/merge |
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/run-all-tests |
This was referenced Mar 3, 2020
This was referenced Jun 23, 2020
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What problem does this PR solve?
The Go 1.14 introduces new instrumentation to check that Go code is following
unsafe.Pointersafety rules dynamically. The new flag-d=checkptris enabled by default with the-raceor-msanflags.Specifically,
-d=checkptrchecks the following:*T, the resulting pointer must be aligned appropriately forT.unsafe.Pointer-typed operands must point into the same object.So if you run unit test with
-racein Go 1.14 you will get a panic likeWhat is changed and how it works?
In fact, the current implementation does not really cause illegal memory access. The
nodestruct is actually a variable-sized struct, thenextsarray is dynamically allocated according to the node's height. ButcheckptrAlignmentwill use the size defined by the struct, which is usually larger than the actual size of the object.As a result, when Go's checker check the memory boundary according to rule 2, it will find some bytes in the
node.nextsdoesn't in the memory space returned by the allocator.To address this problem, I modified the definition of
nodestruct, changenextsarray tonextsBase. Because each node always has at least one element innexts, the checker will never fail.The rule 1 is easy to address, just align the allocation in
arenaBlock.Check List
Tests
-raceusing Go 1.14