__ct_user_enter(9)

✨ NAME ✨

__ct_user_enter(9) — from the Kernel API Manual, bestie — is the function that informs context tracking that the CPU is going to enter user or guest space mode. It’s giving “heads up, we’re switching vibes” energy. 💅

🌸 SYNOPSIS 🌸

void noinstr __ct_user_enter (enum ctx_state state );

🎀 ARGUMENTS 🎀

• state — the userspace context-tracking state to enter. That’s the whole argument, no cap 🌀

💅 DESCRIPTION 💅

okay so this one is a must. This function must be called right before we switch from the kernel to user or guest space. The timing is specifically: when it’s guaranteed that the remaining kernel instructions to execute won’t use any RCU read side critical section. Why? Because this function sets RCU in extended quiescent state. So it’s the little handoff ritual right before user/guest space, and RCU is getting its extended quiescent state moment. ✨

bestie, the “guaranteed” part is doing a lot of work here — the original says the remaining kernel instructions to execute won’t use any RCU read side critical section, and this function sets RCU in extended quiescent state. That’s the whole deal, no cap.

🦋 SEE ALSO 🦋

The kernel file is ./kernel/context_tracking.c, and the whole friend group is:

• ct_nmi_exit(9)
• ct_nmi_enter(9)
• ct_idle_enter(9)
• ct_idle_exit(9)
• ct_irq_enter(9)
• ct_irq_exit(9)
• user_enter_callable(9)
• __ct_user_exit(9)
• user_exit_callable(9)

made with 💖 from ./kernel, stamped October 2026 — that’s the source/version and date, bestie. 🫶