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25.Dd October 12, 2021
26.Dt PTHREAD_SWITCH_ADD_NP 3
27.Os
28.Sh NAME
29.Nm pthread_switch_add_np ,
30.Nm pthread_switch_delete_np
31.Nd thread context switches debugging primitives
32.Sh LIBRARY
33.Lb libpthread
34.Sh SYNOPSIS
35.In pthread_np.h
36.Ft int
37.Fn pthread_switch_add_np "pthread_switch_routine_t routine"
38.Ft int
39.Fn pthread_switch_delete_np "pthread_switch_routine_t routine"
40.Sh DESCRIPTION
41An application is allowed to monitor the thread context switches inside
42the threading library.
43An application can install a routine that gets called every time a thread
44(explicitly created by an application with the
45.Xr pthread_create 3
46function) gets the context switched.
47The routine is passed the thread IDs of the threads that are
48being switched in and out.
49Installation and removal of these hooks may be done using the
50.Fn pthread_switch_add_np
51and
52.Fn pthread_switch_delete_np
53functions respectively.
54.Sh RETURN VALUES
55If successful,
56these functions return 0.
57Otherwise, an error number is returned to indicate the error.
58.Sh ERRORS
59The
60.Fn pthread_switch_add_np
61may fail if:
62.Bl -tag -width Er
63.It Bq Er EINVAL
64.Dv NULL
65pointer was passed in the
66.Fa routine
67argument.
68.El
69.Pp
70The
71.Fn pthread_switch_delete_np
72may fail if:
73.Bl -tag -width Er
74.It Bq Er EINVAL
75The
76.Fa routine
77argument is different from the argument previously passed to the
78.Fn pthread_switch_add_np
79function.
80.El
81.Sh SEE ALSO
82.Xr pthread_create 3 ,
83.Xr pthread_np 3
84.Sh AUTHORS
85This manual page was written by
86.An Alexey Zelkin Aq Mt phantom@FreeBSD.org .
87