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08f02c751b
Sponsored by: The FreeBSD Foundation (cherry picked from commit7fde0187cc) (cherry picked from commit560e22c8fe) (cherry picked from commit5b5fa75acf)
247 lines
6.8 KiB
Groff
247 lines
6.8 KiB
Groff
.\" Copyright (c) 2016 The FreeBSD Foundation, Inc.
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.\"
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.\" This documentation was written by
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.\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship
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.\" from the FreeBSD Foundation.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd May 5, 2020
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.Dt THR_NEW 2
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.Os
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.Sh NAME
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.Nm thr_new
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.Nd create new thread of execution
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/thr.h
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.Ft int
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.Fn thr_new "struct thr_param *param" "int param_size"
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.Sh DESCRIPTION
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.Bf -symbolic
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This function is intended for implementing threading.
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Normal applications should call
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.Xr pthread_create 3
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instead.
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.Ef
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.Pp
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The
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.Fn thr_new
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system call creates a new kernel-scheduled thread of execution in the context
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of the current process.
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The newly created thread shares all attributes of the process with the
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existing kernel-scheduled threads in the process, but has private processor
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execution state.
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The machine context for the new thread is copied from the creating thread's
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context, including coprocessor state.
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FPU state and specific machine registers are excluded from the copy.
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These are set according to ABI requirements and syscall parameters.
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The FPU state for the new thread is reinitialized to clean.
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.Pp
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The
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.Fa param
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structure supplies parameters affecting the thread creation.
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The structure is defined in the
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.In sys/thr.h
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header as follows
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.Bd -literal
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struct thr_param {
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void (*start_func)(void *);
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void *arg;
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char *stack_base;
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size_t stack_size;
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char *tls_base;
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size_t tls_size;
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long *child_tid;
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long *parent_tid;
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int flags;
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struct rtprio *rtp;
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};
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.Ed
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and contains the following fields:
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.Bl -tag -width ".Va parent_tid"
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.It Va start_func
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Pointer to the thread entry function.
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The kernel arranges for the new thread to start executing the function
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upon the first return to userspace.
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.It Va arg
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Opaque argument supplied to the entry function.
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.It Va stack_base
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Stack base address.
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The stack must be allocated by the caller.
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On some architectures, the ABI might require that the system put information
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on the stack to ensure the execution environment for
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.Va start_func .
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.It Va stack_size
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Stack size.
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.It Va tls_base
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TLS base address.
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The value of TLS base is loaded into the ABI-defined machine register
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in the new thread context.
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.It Va tls_size
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TLS size.
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.It Va child_tid
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Address to store the new thread identifier, for the child's use.
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.It Va parent_tid
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Address to store the new thread identifier, for the parent's use.
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.Pp
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Both
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.Va child_tid
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and
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.Va parent_tid
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are provided, with the intent that
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.Va child_tid
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is used by the new thread to get its thread identifier without
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issuing the
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.Xr thr_self 2
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syscall, while
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.Va parent_tid
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is used by the thread creator.
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The latter is separate from
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.Va child_tid
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because the new thread might exit and free its thread data before the parent
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has a chance to execute far enough to access it.
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.It Va flags
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Thread creation flags.
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The
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.Va flags
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member may specify the following flags:
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.Bl -tag -width ".Dv THR_SYSTEM_SCOPE"
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.It Dv THR_SUSPENDED
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Create the new thread in the suspended state.
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The flag is not currently implemented.
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.It Dv THR_SYSTEM_SCOPE
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Create the system scope thread.
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The flag is not currently implemented.
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.El
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.It Va rtp
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Real-time scheduling priority for the new thread.
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May be
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.Dv NULL
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to inherit the priority from the
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creating thread.
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.El
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.Pp
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The
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.Fa param_size
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argument should be set to the size of the
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.Fa param
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structure.
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.Pp
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After the first successful creation of an additional thread,
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the process is marked by the kernel as multi-threaded.
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In particular, the
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.Dv P_HADTHREADS
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flag is set in the process'
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.Dv p_flag
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(visible in the
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.Xr ps 1
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output), and several operations are executed in multi-threaded mode.
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For instance, the
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.Xr execve 2
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system call terminates all threads but the calling one on successful
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execution.
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.Sh RETURN VALUES
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If successful,
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.Fn thr_new
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will return zero, otherwise \-1 is returned, and
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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The
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.Fn thr_new
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operation returns the following errors:
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.Bl -tag -width Er
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.\" When changing this list, consider updating share/man/man3/pthread_create.3,
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.\" since that function can return any of these errors.
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.It Bq Er EFAULT
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The memory pointed to by the
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.Fa param
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argument is not valid.
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.It Bq Er EFAULT
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The memory pointed to by the
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.Fa param
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structure
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.Fa child_tid , parent_tid
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or
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.Fa rtp
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arguments is not valid.
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.It Bq Er EFAULT
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The specified stack base is invalid, or the kernel was unable to put required
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initial data on the stack.
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.It Bq Er EINVAL
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The
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.Fa param_size
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argument specifies a negative value, or the value is greater than the
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largest
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.Fa struct param
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size the kernel can interpret.
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.It Bq Er EINVAL
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The
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.Fa rtp
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member is not
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.Dv NULL
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and specifies invalid scheduling parameters.
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.It Bq Er EINVAL
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The specified TLS base is invalid.
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.It Bq Er EPERM
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The caller does not have permission to set the scheduling parameters or
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scheduling policy.
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.It Bq Er EPROCLIM
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Creation of the new thread would exceed the
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.Dv RACCT_NTHR
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limit, see
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.Xr racct 2 .
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.It Bq Er EPROCLIM
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Creation of the new thread would exceed the
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.Dv kern.threads.max_threads_per_proc
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.Xr sysctl 2
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limit.
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.It Bq Er ENOMEM
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There was not enough kernel memory to allocate the new thread structures.
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.El
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.Sh SEE ALSO
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.Xr ps 1 ,
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.Xr _umtx_op 2 ,
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.Xr execve 2 ,
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.Xr racct 2 ,
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.Xr thr_exit 2 ,
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.Xr thr_kill 2 ,
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.Xr thr_kill2 2 ,
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.Xr thr_self 2 ,
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.Xr thr_set_name 2 ,
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.Xr pthread_create 3
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.Sh STANDARDS
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The
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.Fn thr_new
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system call is non-standard and is used by the
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.Lb libthr
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to implement
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.St -p1003.1-2001
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.Xr pthread 3
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functionality.
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.Sh HISTORY
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The
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.Fn thr_new
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system call first appeared in
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.Fx 5.2 .
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