gh-158552: Wait for Windows threads to suspend before blocking sampling - #158802
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Thanks @pablogsal for the PR 🌮🎉.. I'm working now to backport this PR to: 3.15. |
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GH-158845 is a backport of this pull request to the 3.15 branch. |
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… sampling (GH-158802) (#158845) gh-158552: Wait for Windows threads to suspend before blocking sampling (GH-158802) * gh-158552: Wait for Windows threads to suspend before blocking sampling * Use a named Windows thread enumeration status constant (cherry picked from commit 1643525) Co-authored-by: Pablo Galindo Salgado <Pablogsal@gmail.com>
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…efore blocking sampling (pythonGH-158802) (python#158845)" This reverts commit 31288da.
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Fixes #158552.
On Windows,
NtSuspendProcesscan return before the target's threads have actually stopped. The blocking sampler then reads memory while a thread is still updating it, so suspending the process does not reliably prevent inconsistent frame reads.Wait for each target thread to stop with
GetThreadContextbefore clearing the remote-memory cache and sampling. Enumerate threads withNtGetNextThreadto avoid taking a system-wide thread snapshot on every sample, and resume the process if waiting for suspension fails.--blockingsample-read error rate ~33% on AMD EPYC 9V45 (Windows), ~0.5% on other CPUs #158552