maps__mutate_mapping(9)

💅 maps__mutate_mapping(9)

okay so this is a page from the Kernel API Manual, and bestie, it's a whole vibe. gather round, we're talking about maps__mutate_mapping 🗺️✨

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✨ NAME ✨

maps__mutate_mapping — apply write-protected mutations to a map. literally that's the whole thing, and yes it slays 💖

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🎀 SYNOPSIS 🎀

int maps__mutate_mapping (struct maps *maps , struct map *map , int
(*mutate_cb)(struct map *map, void *data) , void *data );

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🦋 ARGUMENTS 🦋

• maps — the maps collection that contains the map. like, the friend group the map belongs to 🫶
• map — the map you're actually mutating. main character of this call fr 💅
• mutate_cb — the callback function that does the actual mutations. it's giving "you had one job" and it does it ✨
• data — private data you pass along to the callback. little gift bag for your callback 🎁

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🌸 DESCRIPTION 🌸

so what happens is: this acquires the write lock on the maps semaphore, so that concurrent readers are safely protected from ever seeing partially mutated or unsorted map boundaries. no half-finished glow-ups visible to the group chat, periodt 💖

WARNING: 👑 acquiring down_write here can trigger a recursive self-deadlock if the caller already holds the read lock (for example, during maps__for_each_map or maps__find iteration paths that trigger lazy symbol loading). 😭 to completely avoid this deadlock, all kernel/module maps must be pre-loaded up-front (via maps__load_maps) under a clean, single-threaded context before entering multi-threaded event processing loops. no cap, do it in that order or it's giving deadlock 💀

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🌈 SEE ALSO 🌈

kernel file ./tools/perf/util/maps.c — go read it, iykyk 💜

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that's the whole page babes, stay locked and stay safe out there 🧚💅

./tools/perf/util · October 2026 · maps__mutate_mapping(9) — mwah, xoxo, go mutate responsibly 🍓🎀