- Handlers installed with SA_RESETHAND are no longer wrapped, so a deferred one-shot signal can't fall through to the default action.
- Deferred signals are replayed with every signal blocked, so a signal landing mid-replay can't send an entry twice.
- Taking a deferral slot and holding a signal are safe when one signal interrupts another, and a held signal is released only at the nesting level that held it, so a handler's return can't block it again.
- A fifth distinct signal inside a critical section is now held pending with the thread's signal mask and released once the section ends, instead of running its handler while an object lock is held.
- A wait from a signal handler during another wait's sleep uses its own queue and, for a second device, a reference for that call only, so the outer wait keeps its queue and can't return the inner wait's result.
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