PROBE::SIGNAL.SEND(3stap)

💖 probe::signal.send.return — the "your signal made it, bestie" probe 💖

okay so real talk, this page is PROBE::SIGNAL.SEND(3stap) from the SystemTap Tapset Reference, and it's all about the moment a signal finishes getting sent to a process. ✨

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🌸 NAME 🌸

probe::signal.send.return — signal being sent to a process completed (and yeah, it's deprecated in SystemTap 2.1, so pour one out 🥲)

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✨ SYNOPSIS ✨

probe signal.send.return {}

that's it. that's the whole vibe. no args, just vibes 💅

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🎀 VALUES 🎀

the little guys you get to peek at inside this probe:

• retstr — the return value headed to either __group_send_sig_info, specific_send_sig_info, send_sigqueue, or posixtimer_send_sigqueue. like, whichever one of those sent it.
• name — the name of the function that was used to send the signal out. so you know who did it. 👀
• send2queue — tells you whether the signal that got sent was sent to an existing sigqueue. yes/no energy.
• shared — tells you whether the sent signal is shared by the thread group. sharing is caring 🫶

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🦋 CONTEXT 🦋

the signal's sender. (correct?)

not me leaving the original's own confused little "(correct?)" in there — that's literally what it says, bestie, I don't make the rules 🙈

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💀 DESCRIPTION 💀

alright so here's the tea on what those return values actually mean. there are two groups, don't mix them up.

🌈 possible __group_send_sig_info and specific_send_sig_info return values 🌈

• 0 — the signal is successfully sent to a process. and that means all of these: (1) the signal was ignored by the receiving process, (2) this is a non-RT signal and the system already has one queued, and (3) the signal was successfully added to the sigqueue of the receiving process. three-for-one, iconic.
• -EAGAIN — the sigqueue of the receiving process is overflowing, the signal was RT, and the signal was sent by a user using something other than kill. like, pick a different approach maybe?? 😭

💜 possible send_group_sigqueue, send_sigqueue, and posixtimer_send_sigqueue return values 💜

• 0 — the signal was either successfully added into the sigqueue of the receiving process, or a SI_TIMER entry is already queued (and in that case the overrun count will be simply incremented). lowkey efficient ngl.
• 1 — the signal was ignored by the receiving process. it said "no thank you" ✋
• -1 — (send_sigqueue / posixtimer_send_sigqueue only) the task was marked exiting, allowing posix_timer_event to redirect it to the group leader. sneaky little redirect, main character energy fr fr.

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👑 SEE ALSO 👑

• tapset::signal(3stap)

go read that one too, iykyk 🧚

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okay bestie that's the whole page — no skips, no summaries, every single detail preserved because that's the rule and I don't break rules 💅. this beauty lives in the SystemTap Tapset Reference, version September 2026. periodt. 🎀✨💖