sys_pidfd_send_signal(9)

✨ sys_pidfd_send_signal(9) ✨

okay bestie so this one lives in the Kernel API Manual and it's literally about yeeting a signal at a process through a pidfd 💅 it's a kernel-space function, not your cute little userspace syscall wrapper, so lock in 🫶

---

🌸 NAME 🌸

sys_pidfd_send_signal — signal a process through a pidfd. that's it, that's the vibe 💖

---

🎀 SYNOPSIS 🎀

long sys_pidfd_send_signal (int pidfd , int sig , siginfo_t __user *
info , unsigned int flags );

like yes it's one line of C and yes it ate 🔥

---

🦋 ARGUMENTS 🦋

• pidfd — the file descriptor of the process. your little handle to your fave ✨
• sig — the signal to send. the actual message 💌
• info — signal info. the receipts, the extra context 🎀
• flags — future flags. rn it's giving "reserved for later", iykyk 👀

---

🌈 DESCRIPTION 🌈

so here's the tea: this sends the signal to the thread group or to the individual thread, depending on PIDFD_THREAD 👑

and in the future, an extension to flags may be used to override the default scope of the pidfd — so like, the default behavior might get a glow-up option later, no cap 🫶 not today though, that's the future's problem 💀

---

⭐ RETURN ⭐

• 0 on success 💖 slay
• negative errno on failure 😭 it's giving "not today"

---

👑 SEE ALSO 👑

the Kernel file ./kernel/signal.c and its whole friend group, all here in their (9) era 🧚:

• task_set_jobctl_pending(9)
• task_clear_jobctl_trapping(9)
• task_clear_jobctl_pending(9)
• task_participate_group_stop(9)
• ptrace_trap_notify(9)
• force_sig_seccomp(9)
• do_notify_parent_cldstop(9)
• do_signal_stop(9)
• do_jobctl_trap(9)
• do_freezer_trap(9)
• signal_delivered(9)
• sys_restart_syscall(9)
• set_current_blocked(9)
• sys_rt_sigprocmask(9)
• sys_rt_sigpending(9)
• copy_siginfo_to_external32(9)
• do_sigtimedwait(9)
• sys_rt_sigtimedwait(9)
• sys_kill(9)
• sys_tgkill(9)
• sys_tkill(9)
• sys_rt_sigqueueinfo(9)
• sys_sigpending(9)
• sys_sigprocmask(9)
• sys_rt_sigaction(9)
• sys_rt_sigsuspend(9)

---

okay that's the whole page, you're basically a signal expert now, main character energy fr fr 💜 this lil number comes from ./kernel and it's dated October 2026, so like, timestamped and iconic 🎀 periodt ✨