Make the PosixShim errno field into a thread-local#5711
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headius merged 1 commit intojruby:masterfrom Apr 25, 2019
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In order to support concurrent reads and writes via the PosixShim, we need to make errno be a thread-local. Some callers do their own locking, releasing the lock before calling PosixShim, which causes the errno updates and clears to step on other threads. It might be possible to have those callers pass in their "unlock around" logic as shown in jruby#5706, but my first attempt did not work exactly right and may introduces object overhead for stateful lambdas. This implementation introduces thread-local read/write overhead to all accessors of errno, but appears to be a clean way to keep this field safe across concurrent IO operations. Fixes jruby#5706.
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ship it! :) |
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In order to support concurrent reads and writes via the PosixShim,
we need to make errno be a thread-local. Some callers do their own
locking, releasing the lock before calling PosixShim, which causes
the errno updates and clears to step on other threads. It might be
possible to have those callers pass in their "unlock around" logic
as shown in #5706, but my first attempt did not work exactly right
and may introduces object overhead for stateful lambdas.
This implementation introduces thread-local read/write overhead to
all accessors of errno, but appears to be a clean way to keep this
field safe across concurrent IO operations.
Fixes #5706.