From be6116fdfc4d292b77b3df7d4dda029d26a73d65 Mon Sep 17 00:00:00 2001 From: Konstantin Belousov Date: Fri, 1 Oct 2021 04:39:39 +0300 Subject: [PATCH] pthread_mutexattr(3): document each pthread_mutexattr_set/get* function The descriptions may be more elaborated of course, but this is a good step at starting providing any useful information in our man page, at all. Reviewed by: markj Sponsored by: The FreeBSD Foundation MFC after: 3 days Differential revision: https://reviews.freebsd.org/D32243 --- share/man/man3/pthread_mutexattr.3 | 90 +++++++++++++++++++++++++++++- 1 file changed, 88 insertions(+), 2 deletions(-) diff --git a/share/man/man3/pthread_mutexattr.3 b/share/man/man3/pthread_mutexattr.3 index 41f386804151..2a2c5c8d133e 100644 --- a/share/man/man3/pthread_mutexattr.3 +++ b/share/man/man3/pthread_mutexattr.3 @@ -1,6 +1,11 @@ .\" Copyright (C) 2000 Jason Evans . +.\" Copyright (c) 2021 The FreeBSD Foundation, Inc. .\" All rights reserved. .\" +.\" Part of this documentation was written by +.\" Konstantin Belousov under sponsorship +.\" from the FreeBSD Foundation. +.\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: @@ -102,8 +107,89 @@ function destroys .Fa attr . .Pp The -.Fn pthread_mutexattr_set* -functions set the attribute that corresponds to each function name. +.Fn pthread_mutexattr_setprioceiling +function sets the priority ceiling for the mutex, used +by threads executed under the +.Dv PTHREAD_PRIO_PROTECT +protocol. +.Pp +The +.Fn pthread_mutexattr_setprotocol +function specifies the protocol to be followed in utilizing mutexes. +The +.Fa protocol +argument can take one of the following values: +.Bl -tag -width PTHREAD_PRIO_PROTECT +.It PTHREAD_PRIO_NONE +Priority and scheduling of the thread owning this mutex is not +affected by its mutex ownership. +.It PTHREAD_PRIO_INHERIT +Request priority-inheritance protocol, where the thread owning the mutex +is executed at the highest priority among priorities of all threads waiting +on any mutex owned by this thread. +.It PTHREAD_PRIO_PROTECT +Request priority-inheritance protocol, where the thread owning the mutex +is executed at highest priority among priorities or priority ceilings of +all threads waiting on any mutex owned by this thread. +.El +.Pp +The +.Fn pthread_mutexattr_setrobust +function specifies robustness attribute of the mutex. +Possible values for the +.Fa robust +argument are +.Bl -tag -width PTHREAD_MUTEX_STALLED +.It PTHREAD_MUTEX_STALLED +No special actions are taken if the thread owning the mutex is terminated +without unlocking the mutex lock. +This can lead to deadlocks if no other thread can unlock the mutex. +This is the default value. +.It PTHREAD_MUTEX_ROBUST +If the process containing the owning thread of a robust mutex, or owning +thread, terminates while holding the mutex lock, the next thread that +acquires the mutex is notified about the termination +by the return value +.Ev EOWNERDEAD +from the locking function. +Then, either +.Xr pthread_mutex_consistent 3 +can be used to repair the mutex lock state, or +.Xr pthread_mutex_unlock 3 +can unlock the mutex lock but also put it an unusable state, +where all further attempts to acquire it result in the +.Ev ENOTRECOVERABLE +error. +.El +.Pp +The +.Fn pthread_mutexattr_settype +function sets the type of the mutex. +The type affects the behavior of calls which lock and unlock the mutex. +The possible values for the +.Fa type +argument are +.Bl -tag -width PTHREAD_MUTEX_ERRORCHECK +.It PTHREAD_MUTEX_NORMAL +Both recursive locking, and unlocking when the lock is not owned by the current +thread, cause an error to be returned from the corresponding functions. +This matches +.Dv PTHREAD_MUTEX_ERRORCHECK +but somewhat contradicts the behavior mandated by POSIX. +.It PTHREAD_MUTEX_ERRORCHECK +Both recursive locking, and unlocking when the lock is not owned by the current +thread, cause an error returned from the corresponding functions. +.It PTHREAD_MUTEX_RECURSIVE +Recursive locking is allowed. +Attempt to unlock when current thread is not an owner of the lock causes +an error to be returned. +.It PTHREAD_MUTEX_DEFAULT +The +.Fx +implementation maps this type to +.Dv PTHREAD_MUTEX_ERRORCHECK +type. +.El .Pp The .Fn pthread_mutexattr_get*