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pthread_attr_get_np(3): Revamp

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Fix and more thoroughly describe the attributes object lifecycle.

Also, correct the text about which attributes' values are reported.

Add the ENOMEM error.

While here, rephrase unclear passages, add references and fix the
example's style.

Reviewed by:            kib, emaste
Approved by:            emaste (mentor)
MFC after:              2 weeks
Sponsored by:           The FreeBSD Foundation
Differential Revision:  https://reviews.freebsd.org/D43330
This commit is contained in:
Olivier Certner 2024-01-05 14:14:48 +01:00
parent aadb4a1b3f
commit 6211cd4be3
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1 changed files with 49 additions and 35 deletions
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84
share/man/man3/pthread_attr_get_np.3
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@ -1,5 +1,10 @@
.\" Copyright (c) 2002,2003 Alexey Zelkin <phantom@FreeBSD.org>
.\" All rights reserved.
.\" Copyright (c) 2024 The FreeBSD Foundation
.\"
.\" Portions of this documentation were written by Olivier Certner
.\" <olce@FreeBSD.org> at Kumacom SARL 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
@ -22,12 +27,12 @@
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.Dd October 12, 2021
.Dd January 5, 2024
.Dt PTHREAD_ATTR_GET_NP 3
.Os
.Sh NAME
.Nm pthread_attr_get_np
.Nd get attributes of existent thread
.Nd get attributes of an existing thread
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
@ -37,51 +42,54 @@
.Sh DESCRIPTION
The
.Fn pthread_attr_get_np
function is used to get existent thread's attributes.
Most fields of
.Vt pthread_attr_t
structure are exact values of attributes provided at thread creation
time (as parameter to
.Xr pthread_create 3
function), except for the stack address.
.Pp
Value returned as
.Fa dst
is supposed to be used in conjunction with
.Fn pthread_attr_get*
functions to retrieve individual values from
function is used to retrieve the attributes of the specified thread into an
existing
.Vt pthread_attr_t
structure.
Parameter
.Fa dst
should point to allocated memory area big enough to fit this structure.
The attributes' values are the current ones for the target thread, except for
the stack top address if not properly aligned for the architecture, since in
this case its value has been adjusted internally before use.
.Pp
It is HIGHLY RECOMMENDED to use
Argument
.Fa dst
must be a pointer to a valid attributes object
.Po
it was initialized at some point by
.Xr pthread_attr_init 3
function to allocate attribute storage.
.Sh IMPLEMENTATION NOTES
The
.Fn pthread_attr_get_np
function will always return a pointer to the thread's real stack address,
regardless of its value in the original attributes structure.
and was not destroyed since then
.Pc .
After a successful call to
.Fn pthread_attr_get_np ,
the individual attributes' values can be retrieved as usual via the
corresponding accessor functions as documented in
.Xr pthread_attr 3 .
After a failed call to
.Fn pthread_attr_get_np ,
the object pointed to by
.Fa dst
is left unmodified, and can continue to be used as if the failed call never
happened.
.Sh RETURN VALUES
If successful,
.Fn pthread_attr_get_np
function returns 0.
Otherwise, an error number is returned to indicate the error.
.Sh EXAMPLES
This function retrieves the stack size of the thread specified by the
.Fa pid
argument:
.Bd -literal
size_t
my_thread_stack_size(pthread_t pid)
my_thread_stack_size(pthread_t tid)
{
pthread_attr_t attr;
size_t size;
pthread_attr_t attr;
size_t size;
pthread_attr_init(&attr);
pthread_attr_get_np(pid, &attr);
pthread_attr_getstacksize(&attr, &size);
pthread_attr_destroy(&attr);
return(size);
pthread_attr_init(&attr);
pthread_attr_get_np(tid, &attr);
pthread_attr_getstacksize(&attr, &size);
pthread_attr_destroy(&attr);
return (size);
}
.Ed
.Sh ERRORS
@ -90,12 +98,16 @@ The
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid value for one of given parameters.
One of the arguments has an invalid value.
.It Bq Er ESRCH
No thread could be found corresponding to that specified by the given
thread ID.
.It Bq Er ENOMEM
There was not enough memory to allocate additional storage needed by the attributes
object's implementation.
.El
.Sh SEE ALSO
.Xr pthread_attr 3 ,
.Xr pthread_attr_destroy 3 ,
.Xr pthread_attr_getdetachstate 3 ,
.Xr pthread_attr_getinheritsched 3 ,
@ -111,4 +123,6 @@ thread ID.
The
.Fn pthread_attr_get_np
function and this manual page were written by
.An Alexey Zelkin Aq Mt phantom@FreeBSD.org .
.An Alexey Zelkin Aq Mt phantom@FreeBSD.org ,
and the latter was revised by
.An Olivier Certner Aq Mt olce@FreeBSD.org .