Don't use callbacks when performing sync IO with async handles#126845
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…vent for sync IO with async handles Instead of using ThreadPoolBoundHandle callbacks and reference counting when performing synchronous IO with async file handles, allocate the NativeOverlapped directly via NativeMemory and set the low-order bit of hEvent to suppress I/O completion port notifications. This eliminates the CallbackResetEvent class, the s_callback field, and the AllocateCallback/GetNativeOverlappedForAsyncHandle methods, reducing allocations and complexity. Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/d7a61400-c63f-401a-9503-0313459af6f7 Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>
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[WIP] Remove callbacks for sync IO operations with async handles
Don't use callbacks when performing sync IO with async handles
Apr 13, 2026
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Tagging subscribers to this area: @dotnet/area-system-io |
adamsitnik
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Apr 14, 2026
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@copilot please address my feedback (nits)
…appedWithEventHandle Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/bcdd8838-718e-4561-abf4-90c9c2deb905 Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>
Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>
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jkotas
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Jun 9, 2026
This reverts commit 569ccce.
…iveOverlapped.EventHandle
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jkotas
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Jun 10, 2026
This was referenced Jun 10, 2026
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I can see that most of the Windows CI legs are timeing out after giving up on As of now, I can't reproduce it locally (I can run all tests in less than 12 minutes) Details.\build.cmd -c release -subset clr+libs+libs.tests
.\build.cmd -c release -subset libs.tests -test -testnobuild |
This was referenced Jun 12, 2026
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/ba-g the bad exit for linux test run of "System.Security.Cryptography.Tests is unrelated |
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Description
When performing synchronous I/O on async file handles (
FILE_FLAG_OVERLAPPED),RandomAccess.Windows.cspreviously usedThreadPoolBoundHandle.UnsafeAllocateNativeOverlappedwith anIOCompletionCallbackand a customCallbackResetEventclass that tracked a reference count to handle the race between the IOCP callback and the caller'sGetOverlappedResult.This callback path is unnecessary. Setting the low-order bit of
hEventin theOVERLAPPEDstructure prevents the I/O completion from being queued to the completion port, eliminating the callback.This reduces complexity and allocations, preserves managed wait behavior, fixes correctness issues in both error handling and exceptional wait paths, and hardens handle lifetime safety in the sync-over-async path.