dlopen: make error handling thread safe #431
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The dlerror() value is stored in thread local storage and thus checking the error from go code is not safe because go can schedule goroutines on any other thread at any time. This means it is possible that between the dlsym() or dlclose() call the code get moved to another thread and thus the dlerror() value is not what we expect. Instead because we read now from another thread it will be an error from a different call. A test is added which without this fix is able to reproduce the problem somewhat reliably. This issue was observed in the podman CI[1] which uses the sdjournal API. [1] containers/podman#20569 Signed-off-by: Paul Holzinger <[email protected]>
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Example failure with the new test but without the locked thread: |
cgwalters
approved these changes
Nov 3, 2023
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Thanks for the quick review/merge @cgwalters |
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Nice digging on this! |
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The dlerror() value is stored in thread local storage and thus checking the error from go code is not safe because go can schedule goroutines on any other thread at any time. This means it is possible that between the dlsym() or dlclose() call the code get moved to another thread and thus the dlerror() value is not what we expect. Instead because we read now from another thread it will be an error from a different call.
A test is added which without this fix is able to reproduce the problem somewhat reliably.
This issue was observed in the podman CI[1] which uses the sdjournal API.
[1] containers/podman#20569