cherry-pick(4.3-stable): Android ANR deadlock between CSS updates-registry lock and Fabric commit (#9715)#9849
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MatiPl01 merged 2 commits intoJul 3, 2026
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…he commit deadlock Resolving a relative CSS length (e.g. a transformOrigin mixing % and px) read the live ShadowTree, which takes the ShadowTree commit lock, while the CSS flush holds the updates-registry lock; a concurrent Fabric commit takes the same two locks in the opposite order, so they deadlock (AB-BA) when RN's preventShadowTreeCommitExhaustion flag holds the commit lock across the commit hooks. This branch got that lock shape with #9323, which replaced the per-registry flush locks with the single updates-registry lock the commit hook also takes. Port of #9715's approach to 4.3: ReanimatedMountHook records the mounted root per surface and ViewStylesRepository resolves nodes from that snapshot via plain tree walks, so the read path never takes the ShadowTree lock. Unlike main, transition setup here resolves relative lengths on the JS thread without the updates-registry lock, so the snapshot map is guarded by its own leaf mutex.
tomekzaw
approved these changes
Jul 3, 2026
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Summary
Cherry-picking for Reanimated 4.3.2 release
The original commit doesn't apply to 4.3-stable, so this PR ports the analogous fix. Two adjustments: there's no
USE_ANIMATION_BACKENDbranch (4.3 has no animation backend), and the snapshot map gets its own mutex because 4.3 also resolves relative lengths on the JS thread, outside the registry lock.