Raion at 23:59, 9 January 2026

2026-01-09T23:59:42Z

← Older revision		Revision as of 23:59, 9 January 2026
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	Differences: Separate syscalls instead of unified schedctl; weaker real-time support.		Differences: Separate syscalls instead of unified schedctl; weaker real-time support.
	Overall, IRIX provides a rich unified scheduling interface (schedctl) with strong real-time extensions (FRS, fixed-priority) while maintaining compatibility with both SVR4 and BSD/POSIX. For reimplementation, focus on vproc dispatch and dual semantics; FRS is IRIX-specific.		Overall, IRIX provides a rich unified scheduling interface (schedctl) with strong real-time extensions (FRS, fixed-priority) while maintaining compatibility with both SVR4 and BSD/POSIX. For reimplementation, focus on vproc dispatch and dual semantics; FRS is IRIX-specific.

			[[Category: Kernel Documentation]]

Raion: Created page with "== Overview == IRIX has many syscalls grouped by core process identity, time management, scheduling control, profiling, and signal-related system calls in the IRIX kernel. These calls operate on vproc_t (virtual process) structures, which encapsulate state shared across threads (uthreads) in multi-threaded processes. Key areas: Time retrieval/setting UID/GID manipulation (System V and BSD semantics) Process group/session control Nice value and real-time priority adjustm..."

2026-01-04T03:48:49Z

Created page with "== Overview == IRIX has many syscalls grouped by core process identity, time management, scheduling control, profiling, and signal-related system calls in the IRIX kernel. These calls operate on vproc_t (virtual process) structures, which encapsulate state shared across threads (uthreads) in multi-threaded processes. Key areas: Time retrieval/setting UID/GID manipulation (System V and BSD semantics) Process group/session control Nice value and real-time priority adjustm..."

New page

== Overview ==
IRIX has many syscalls grouped by core process identity, time management, scheduling control, profiling, and signal-related system calls in the IRIX kernel. These calls operate on vproc_t (virtual process) structures, which encapsulate state shared across threads (uthreads) in multi-threaded processes.
Key areas:

Time retrieval/setting
UID/GID manipulation (System V and BSD semantics)
Process group/session control
Nice value and real-time priority adjustments
Profiling (clock-based, shared-library, R10000 event counters)
Signal blocking/masking, pending checks, suspend, handler installation, alternate stacks
Miscellaneous (pause, umask, ulimit, vhangup, sysconf)

The implementation blends System V, BSD, and POSIX behaviors, with extensions for IRIX-specific features (e.g., Frame Scheduler via schedctl).
== Key Functions ==
Time Management

gtime: Returns current time-of-day in seconds.
stime: Sets system clock.
alarm: Sets interval timer on real-time clock.
times: Returns process and child CPU times.

Identity Management

setuid / setreuid: Set real/effective UID.
setgid / setregid: Set real/effective GID (with XPG4 variant for saved-GID semantics).
getuid / getgid: Return real and effective IDs.
setgroups / getgroups: Manage supplementary group list.
umask: Set/get file creation mask (per-uthread, shared).

Process Group and Session

setpgrp: System V style (flag=0 returns pgid).
BSDsetpgrp / BSDgetpgrp: BSD compatibility.
setpgid: POSIX version.
setsid: Create new session.

Scheduling and Priority

nice: Adjust nice value.
schedctl: Unified interface for:
Real-time fixed priority
Time slice setting
Nice adjustments (process, pgrp, user-wide via plistscan)
CPU affinity
Scheduling mode (free/gang)
Frame Scheduler (FRS) operations
Legacy hooks

Profiling

profil: Traditional clock-based profiling.
sprofil: Shared-library profiling.
evc_profil: R10000 hardware event counter profiling (per-thread counters).

Signal Handling

sigpending: Return pending signal set.
sigsuspend: Atomically swap signal mask and sleep.
sigprocmask: Block/unblock signals.
sigaction: Install signal handler with mask/flags.
sigstack / sigaltstack: Set/query alternate signal stack (with XPG4 corrected behavior).

Miscellaneous

pause: Sleep until signal.
ulimit: Query/set resource limits (file size, data segment, descriptors).
vhangup: Invalidate controlling terminal.
sysconf: Runtime configuration values (e.g., _SC_ARG_MAX, _SC_NGROUPS_MAX).

== Undocumented or IRIX-Specific Interfaces and Behaviors ==
vproc_t-Centric Design
All process-wide operations dispatch through VPROC_ macros on curvprocp, supporting shared state across uthreads.
Dual Semantics

System V (setpgrp) and BSD/POSIX (setpgid, setsid) co-exist.
XPG4 variants for sigaltstack (correct stack direction) and setregid (saved-GID handling).

schedctl Extensions

Real-time fixed priorities (non-degrading).
Gang scheduling modes.
Full Frame Scheduler (FRS) user interface for hard real-time gangs.
User-wide nice operations via process table scan.

Profiling Variants

Clock-based, shared-library, and hardware counter (R10000) profiling.
Fast profiling mode.

Signal Stack Handling

Historical IRIX sigaltstack required user to account for stack growth direction; XPG4 variant fixes this.

== Similarities to illumos and BSD Kernel Implementations ==
illumos (Solaris-derived)
Strong overlap:

UID/GID, nice, alarm, times, pause, umask, ulimit nearly identical.
priocntl(2) analogous to schedctl for real-time classes.
Signal syscalls match POSIX.
Alternate stack via sigaltstack.

Differences: No direct FRS; different real-time model.
BSD (FreeBSD, etc.)
Close matches:

setreuid, setregid, setpgid, setsid, nice, getpriority/setpriority.
Signal interfaces standard.
sysconf for configuration.

Differences: Separate syscalls instead of unified schedctl; weaker real-time support.
Overall, IRIX provides a rich unified scheduling interface (schedctl) with strong real-time extensions (FRS, fixed-priority) while maintaining compatibility with both SVR4 and BSD/POSIX. For reimplementation, focus on vproc dispatch and dual semantics; FRS is IRIX-specific.

Kernel: Process/Time Management Syscalls - Revision history

Raion at 23:59, 9 January 2026