mmu_interval_read_begin(9)

🎀 NAME 🎀

okay so bestie, this is mmu_interval_read_begin(9) from the Kernel API Manual 💖 and it does exactly what it says on the tin: begin a read side critical section against a VA range. no cap, iconic behavior.

✨ SYNOPSIS ✨

unsigned long mmu_interval_read_begin (struct mmu_interval_notifier
*interval_sub );

🦋 ARGUMENTS 🦋

• interval_sub — the interval subscription 🫶

🔥 DESCRIPTION 🔥

okay so the mmu_iterval_read_begin/mmu_iterval_read_retry duo implements a collision-retry scheme similar to seqcount for the VA range under subscription. vibe check: if the mm invokes invalidation during the critical section, then mmu_interval_read_retry will return true. that's the whole point, periodt.

this is useful to obtain shadow PTEs where teardown or setup of the SPTEs require a blocking context. the critical region formed by this can sleep, and the required 'user_lock' can also be a sleeping lock. 😭 yes bestie, sleeping locks are invited to the function.

the caller is required to provide a 'user_lock' to serialize both teardown and setup. do not skip this, fr fr.

the return value should be passed to mmu_interval_read_retry. that's the handoff, bestie 🫶

🌈 SEE ALSO 🌈

• Kernel file ./mm/mmu_notifier.c
• mmu_notifier_register(9)
• mmu_notifier_get_locked(9)
• mmu_notifier_put(9)
• mmu_interval_notifier_insert(9)
• mmu_interval_notifier_remove(9)
• mmu_notifier_synchronize(9)

mwah 💋 source/version vibes: ./mm; date: October 2026. bye bestie 🌸