find_sub_ctxt(9)

✨ find_sub_ctxt(9) ✨

okay so this is a page from the Kernel API Manual — yes bestie, the kernel has lore too 💅 and today's main character is find_sub_ctxt. Let's get into it 🫶

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🌸 NAME 🌸

find_sub_ctxt — fund sub-context

(it's giving "short and mysterious," and honestly? iconic.)

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🎀 SYNOPSIS 🎀

int find_sub_ctxt (struct hfi1_filedata *fd , const struct
       hfi1_user_info *uinfo );

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🦋 ARGUMENTS 🦋

• fd — a valid filedata pointer. literally has to be valid, no cap 🙈
• uinfo — the matching info you use to find a possible context to share.

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💖 DESCRIPTION 💖

So here's the vibe check: the hfi1_mutex must be held when this function is called. Not optional, not "ehhh maybe," it's a whole requirement 🔥

Why? Because it's necessary to ensure serialized creation of shared contexts. Like, no two of them racing in there at the same time — we keep that line single-file, periodt 👑

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⭐ RETURN ⭐

• 0 — no sub-context found 😔
• 1 — subcontext found and allocated 🎉 slay
• errno:
  • EINVAL — incorrect parameters 🙈
  • EBUSY — all sub contexts in use 💀 sorry bestie, they're all taken

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🌈 SEE ALSO 🌈

Kernel file ./drivers/infiniband/hw/hfi1/file_ops.c, plus the whole friend group 😭💜

• complete_subctxt(9)
• match_ctxt(9)
• user_exp_rcv_setup(9)
• user_exp_rcv_clear(9)
• user_exp_rcv_invalid(9)
• manage_rcvq(9)
• ctxt_reset(9)

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and that's the page, bestie 🧚✨ it lives down in ./drivers/infiniband/hw/hfi1, and this little masterpiece is dated October 2026 — future vibes only 🍓👑 go forth and hold that mutex 💅