PTHREAD_MUTEX_CONSISTENT_NP(3)

💖 pthread_mutex_consistent(3) 💖

okay bestie, welcome to the Library Functions Manual section of the group chat — this one's from the POSIX threads library (libpthread, -lpthread) and it's honestly kind of a big deal for anyone whose threads keep ghosting them mid-lock. 👻

✨ NAME ✨

pthread_mutex_consistent — make a robust mutex consistent 🫶

🌸 LIBRARY 🌸

POSIX threads library (libpthread, -lpthread)

🦋 SYNOPSIS 🦋

#include <pthread.h>

int pthread_mutex_consistent(pthread_mutex_t *mutex);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

pthread_mutex_consistent():
    _POSIX_C_SOURCE >= 200809L

yes you literally need that macro bestie, glibc does not play about feature test macros 💅

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💅 DESCRIPTION 💅

So here's the vibe: this function makes a robust mutex consistent again if it's sitting in an inconsistent state. 🎀

And how does a mutex end up inconsistent, you ask? Not me about to tell you the lore: a mutex can be left in an inconsistent state if its owner terminates while holding the mutex. 💀 In that case, the next owner who acquires the mutex will succeed, and they get notified by a return value of EOWNERDEAD from a call to pthread_mutex_lock(). Like, surprise!! you own the lock now, and also everything it was protecting might be a crime scene. 😭

The way that pthread_mutex_consistent() is the "okay I cleaned it up, we're good" button. ✨

👑 RETURN VALUE 👑

• On success, pthread_mutex_consistent() returns 0. slay.
• Otherwise, it returns a positive error number to indicate the error. (positive, not negative, not errno-flavoured — the return value is the error, iykyk) 🙈

🍓 ERRORS 🍓

• EINVAL — The mutex is either not robust or is not in an inconsistent state. (Translation: you're asking the function to fix a vibe that was never broken, or that it literally cannot fix. 🧚)

⭐ STANDARDS ⭐

POSIX.1-2008.

🌈 HISTORY 🌈

• glibc 2.12. 🎉
• POSIX.1-2008.

Now for the ancient lore: before pthread_mutex_consistent() got added to POSIX, glibc defined the following equivalent nonstandard function if _GNU_SOURCE was defined:

[[deprecated]]
int pthread_mutex_consistent_np(const pthread_mutex_t *mutex);

This GNU-specific API, which first appeared in glibc 2.4, is nowadays obsolete and should not be used in new programs; since glibc 2.34 it has been marked as deprecated. so like... don't. 🚫 no cap, don't use the _np one, it's giving 2008 and not in the cute vintage way.

💜 NOTES 💜

pthread_mutex_consistent() simply informs the implementation that the state (shared data) guarded by the mutex has been restored to a consistent state and that normal operations can now be performed with the mutex. 🫶

🚨 IMPORTANT BESTIE 🚨 It is the application's responsibility to ensure that the shared data has been restored to a consistent state before calling pthread_mutex_consistent(). The function is not doing your cleanup for you. It is not a magical healer. It is a notary. You do the work, it signs the papers. 💅

🎀 EXAMPLES 🎀

See pthread_mutexattr_setrobust(3). (yes go look, the example lives over there, I'm not retyping it, go read it, ily 🫶)

💖 SEE ALSO 💖

• pthread_mutex_lock(3)
• pthread_mutexattr_getrobust(3)
• pthread_mutexattr_init(3)
• pthread_mutexattr_setrobust(3)
• pthreads(7)

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okay that's the whole page, you ate that fr fr 🍽️✨ remember: robust mutexes are main character energy but you still have to restore the shared data yourself, no one else is coming to do it for you. 💀🫶

Linux man-pages 6.20 — dated 2026-02-08 — mwah, that's the version and the date, love u, bye bestie 💕🌈👑 page (PTHREAD_MUTEX_CONSISTENT(3)) closed, periodt. 🎀