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CP-49129: Drop global lock around sexpr parsing #5682

Merged
merged 6 commits into from
Jun 12, 2024
Merged

CP-49129: Drop global lock around sexpr parsing #5682

merged 6 commits into from
Jun 12, 2024

Commits on Jun 12, 2024

  1. CP-49129: Add unit test for parallel parsing. 

    Initial commit message:

"Provides simple code to generate S-expression trees and attempt to parse them
across a large number of threads. It serves to demonstrate that ocamlyacc's
generated parses are not thread-safe (in that they modify a global variable
"env")."

Move Colin's unit test for parallel parsing into xapi.

Signed-off-by: Colin Barr <colin.barr@cloud.com>
Signed-off-by: Gabriel Buica <danutgabriel.buica@cloud.com>
    @contificate @GabrielBuica
    contificate authored and GabrielBuica committed Jun 12, 2024
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  2. CP-49129: Make unit test run on alcotest. 

    Make `test_sexpr` run using alcotest.

Signed-off-by: Gabriel Buica <danutgabriel.buica@cloud.com>
    @GabrielBuica
    GabrielBuica committed Jun 12, 2024
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  3. CP-49129: Replace ocamlyacc with menhir 

    From https://ocaml.org/manual/5.1/lexyacc.html on ocamlyacc concurrency
sefety:

"Parsers generated by ocamlyacc are not thread-safe. Those parsers rely
on an internal work state which is shared by all ocamlyacc generated parsers.
The menhir parser generator is a better option if you want thread-safe parsers."

We currently hold a global lock while calling the sexpr parser, so even if we
try to parse a small sexpression, it'll be blocked behind parsing the large one.

Switch to Menhir to make this thread-safe.

Signed-off-by: Gabriel Buica <danutgabriel.buica@cloud.com>
    @GabrielBuica
    GabrielBuica committed Jun 12, 2024
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  4. CP-49129: Drop global lock around sexpr parsing 

    Using `ocamlyacc` with this change results in a test failure. Thus
showing the issue of parallel parsing using `ocamlyacc`.

Signed-off-by: Gabriel Buica <danutgabriel.buica@cloud.com>
    @GabrielBuica
    GabrielBuica committed Jun 12, 2024
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  5. CP-49045: replace all uses of ocamlyacc with menhir which is thread-safe 

    Signed-off-by: Edwin Török <edwin.torok@cloud.com>
    @edwintorok @GabrielBuica
    edwintorok authored and GabrielBuica committed Jun 12, 2024
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  6. CP-49129: Update quality-gate.sh for ocamlyacc 

    We want to be sure there are no more uses of `ocamlyacc`, because of
concurrency issues.

Menhir should be used instead.

Signed-off-by: Gabriel Buica <danutgabriel.buica@cloud.com>
    @GabrielBuica
    GabrielBuica committed Jun 12, 2024
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