GH-909: Fix KexOutputHandler self-deadlock on inline write failure during shutdown#910
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tomaswolf merged 1 commit intoJul 23, 2026
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Can you please put the PR description minus the "Fixes #909" line into the commit message? Good commit messages are important, especially in OSS. For future contributors and maintainers it is very helpful if the commit messages explain the reasoning behind a change as it makes it much easier to figure out the history via |
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Done, I've moved the explanation into the commit message (subject + body) and force-pushed. Thanks for the nudge; fully agree the reasoning belongs in git rather than only in the PR. |
…ure during shutdown When a write started under the read lock in writeOrEnqueue() fails inline, the session close re-enters KexOutputHandler.shutdown()→updateState(), which tries to take the write lock on the same thread — an illegal read-to-write upgrade that self-deadlocks. Fix: in shutdown(), when the current thread already holds the read lock (getReadHoldCount() > 0), update the state without acquiring the write lock. The read lock already excludes writers, so it stays consistent; KEX write-ordering is unchanged. Includes a deterministic regression test (hangs without the fix, passes with it).
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Fixes #909.
When a write started under the read lock in
writeOrEnqueue()fails inline, the session close re-enters KexOutputHandler.shutdown()→updateState()`, which tries to take the write lock on the same thread — an illegal read-to-write upgrade that self-deadlocks.Fix: in
shutdown(), when the current thread already holds the read lock (getReadHoldCount() > 0), update the state without acquiring the write lock. The read lock already excludes writers, so it stays consistent; KEX write-ordering is unchanged.Includes a deterministic regression test (hangs without the fix, passes with it).