Re: [PATCH v4 3/4] man/man2/prctl.2, PR_FUTEX_HASH_GET_SLOTS.2const: Document PR_FUTEX_HASH_GET_SLOTS

Alejandro Colomar
2025-06-11T08:52:42Z

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Hi Sebastian,

On Mon, Jun 02, 2025 at 04:01:03PM +0200, Sebastian Andrzej Siewior wrote:
> Reviewed-by: Alejandro Colomar <alx@kernel.org>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> man/man2const/PR_FUTEX_HASH_GET_SLOTS.2const | 37 ++++++++++++++++++++
> man/man2const/PR_FUTEX_HASH_SET_SLOTS.2const | 7 ++--
> 2 files changed, 40 insertions(+), 4 deletions(-)
> create mode 100644 man/man2const/PR_FUTEX_HASH_GET_SLOTS.2const
>
> diff --git a/man/man2const/PR_FUTEX_HASH_GET_SLOTS.2const b/man/man2const/PR_FUTEX_HASH_GET_SLOTS.2const
> new file mode 100644
> index 0000000000000..f5c6380ef1fe7
> --- /dev/null
> +++ b/man/man2const/PR_FUTEX_HASH_GET_SLOTS.2const
> @@ -0,0 +1,37 @@
> +.\" Copyright, the authors of the Linux man-pages project
> +.\"
> +.\" SPDX-License-Identifier: Linux-man-pages-copyleft
> +.\"
> +.TH PR_FUTEX_HASH_GET_SLOTS 2const (date) "Linux man-pages (unreleased)"
> +.SH NAME
> +PR_FUTEX_HASH_GET_SLOTS
> +\-
> +return the size of the private hash
> +.SH LIBRARY
> +Standard C library
> +.RI ( libc ,\~ \-lc )
> +.SH SYNOPSIS
> +.nf
> +.BR "#include <linux/prctl.h>" " /* Definition of " PR_* " constants */"
> +.B #include <sys/prctl.h>
> +.P
> +.B int prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_GET_SLOTS);
> +.fi
> +.SH DESCRIPTION
> +Return the current size of the private hash.
> +.SH RETURN VALUE
> +A value of 0 means that a private hash has not been allocated
> +and the global hash is in use.
> +A value >0 specifies the size of the private hash.
> +On error, \-1 is returned, and
> +.I errno
> +is set to indicate the error.
> +.SH STANDARDS
> +Linux.
> +.SH HISTORY
> +Linux 6.16.
> +.SH SEE ALSO
> +.BR prctl (2),
> +.BR PR_FUTEX_HASH (2const),
> +.BR PR_FUTEX_HASH_GET_IMMUTABLE (2const),
> +.BR PR_FUTEX_HASH_SET_SLOTS (2const)
> diff --git a/man/man2const/PR_FUTEX_HASH_SET_SLOTS.2const b/man/man2const/PR_FUTEX_HASH_SET_SLOTS.2const
> index 1f08d1bb30485..531e3bcca112d 100644
> --- a/man/man2const/PR_FUTEX_HASH_SET_SLOTS.2const
> +++ b/man/man2const/PR_FUTEX_HASH_SET_SLOTS.2const
> @@ -29,7 +29,7 @@ Specifies the size of private hash to allocate.
> Use the global hash.
> This is the behaviour used before 6.16.
> The operation implies the
> -.I FH_FLAG_IMMUTABLE
> +.B FH_FLAG_IMMUTABLE

This seems like a rebase accident. This does not belong in this patch.
A few others below too.

Cheers,
Alex

> flag.
> .TP
> .I >0
> @@ -38,7 +38,7 @@ The value must be power of two and the lowest possible value is 2.
> The upper limit depends on the available memory in the system.
> Each slot requires 64bytes of memory.
> Kernels compiled with
> -.I CONFIG_PROVE_LOCKING
> +.B CONFIG_PROVE_LOCKING
> will consume more than that.
> .RE
> .TP
> @@ -46,7 +46,7 @@ will consume more than that.
> .RS
> The following flags can be specified:
> .TP
> -.I FH_FLAG_IMMUTABLE
> +.B FH_FLAG_IMMUTABLE
> The private hash can no longer be changed.
> By using an immutable private hash
> the kernel can avoid some accounting for the data structure.
> @@ -54,7 +54,6 @@ This accounting is visible in benchmarks if many
> .BR futex (2)
> operations are invoked in parallel on different CPUs.
> .RE
> -.RE
> .SH RETURN VALUE
> On success,
> 0 is returned.
> --
> 2.49.0
>

--
<https://www.alejandro-colomar.es/>

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