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Message-ID: <e4802e90-75e5-caaa-ea53-bdbe3c6dd17a@gmail.com>
Date: Fri, 27 Nov 2020 11:43:09 +0100
From: "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To: Alejandro Colomar <alx.manpages@...il.com>
Cc: mtk.manpages@...il.com, linux-man@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] spu_create.2: Clarify that one of the prototypes is the
current one
Hi ALex,
On 11/26/20 7:32 PM, Alejandro Colomar wrote:
> The current Linux kernel only provides a definition of 'spu_create()'.
> It has 4 parameters, the last being 'int neighbor_fd'.
>
> Before Linux 2.6.23, there was an older prototype,
> which didn't have this last parameter.
>
> Move that old prototype to VERSIONS,
> and keep the current one in SYNOPSIS.
>
> ......
>
> $ grep -rn "SYSCALL_DEFINE.(spu_create"
> arch/powerpc/platforms/cell/spu_syscalls.c:56:
> SYSCALL_DEFINE4(spu_create, const char __user *, name, unsigned int, flags,
>
> $ sed -n 56,/^}/p arch/powerpc/platforms/cell/spu_syscalls.c
> SYSCALL_DEFINE4(spu_create, const char __user *, name, unsigned int, flags,
> umode_t, mode, int, neighbor_fd)
> {
> long ret;
> struct spufs_calls *calls;
>
> calls = spufs_calls_get();
> if (!calls)
> return -ENOSYS;
>
> if (flags & SPU_CREATE_AFFINITY_SPU) {
> struct fd neighbor = fdget(neighbor_fd);
> ret = -EBADF;
> if (neighbor.file) {
> ret = calls->create_thread(name, flags, mode, neighbor.file);
> fdput(neighbor);
> }
> } else
> ret = calls->create_thread(name, flags, mode, NULL);
>
> spufs_calls_put(calls);
> return ret;
> }
>
> $ git blame arch/powerpc/platforms/cell/spu_syscalls.c -L 56,/\)/
> 1bc94226d5c64 (Al Viro 2011-07-26 16:50:23 -0400 56)
> SYSCALL_DEFINE4(spu_create, const char __user *, name, unsigned int, flags,
> 1bc94226d5c64 (Al Viro 2011-07-26 16:50:23 -0400 57)
> umode_t, mode, int, neighbor_fd)
>
> $ git checkout 1bc94226d5c64~1
> $ git blame arch/powerpc/platforms/cell/spu_syscalls.c -L /spu_create/,/\)/
> 67207b9664a8d (Arnd Bergmann 2005-11-15 15:53:48 -0500 68)
> asmlinkage long sys_spu_create(const char __user *name,
> 8e68e2f248332 (Arnd Bergmann 2007-07-20 21:39:47 +0200 69)
> unsigned int flags, mode_t mode, int neighbor_fd)
>
> $ git checkout 8e68e2f248332~1
> $ git blame arch/powerpc/platforms/cell/spu_syscalls.c -L /spu_create/,/\)/
> 67207b9664a8d (Arnd Bergmann 2005-11-15 15:53:48 -0500 36)
> asmlinkage long sys_spu_create(const char __user *name,
> 67207b9664a8d (Arnd Bergmann 2005-11-15 15:53:48 -0500 37)
> unsigned int flags, mode_t mode)
>
> $ git describe --contains 8e68e2f248332
> v2.6.23-rc1~195^2~7
>
> Signed-off-by: Alejandro Colomar <alx.manpages@...il.com>
> ---
> man2/spu_create.2 | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/man2/spu_create.2 b/man2/spu_create.2
> index 4e6f5d730..3eeafee56 100644
> --- a/man2/spu_create.2
> +++ b/man2/spu_create.2
> @@ -30,9 +30,8 @@ spu_create \- create a new spu context
> .B #include <sys/types.h>
> .B #include <sys/spu.h>
> .PP
> -.BI "int spu_create(const char *" pathname ", int " flags ", mode_t " mode ");"
> -.BI "int spu_create(const char *" pathname ", int " flags ", mode_t " mode ","
> -.BI " int " neighbor_fd ");"
> +.BI "int spu_create(const char *" pathname ", int " flags ", mode_t " mode ,
> +.BI " int " neighbor_fd );
> .fi
> .PP
> .IR Note :
> @@ -247,6 +246,17 @@ By convention, it gets mounted in
> The
> .BR spu_create ()
> system call was added to Linux in kernel 2.6.16.
> +.PP
> +.\" commit 8e68e2f248332a9c3fd4f08258f488c209bd3e0c
> +Before Linux 2.6.23, the prototype for
> +.BR spu_create ()
> +was:
> +.PP
> +.in +4n
> +.EX
> +.BI "int spu_create(const char *" pathname ", int " flags ", mode_t " mode );
> +.EE
> +.in
> .SH CONFORMING TO
> This call is Linux-specific and implemented only on the PowerPC
> architecture.
Thanks for the detailed research. The page was indeed a bit messy
in explaining some details. I've instead opted for a different change;
see below.
Thanks,
Michael
diff --git a/man2/spu_create.2 b/man2/spu_create.2
index 92f5fc304..f09d498ed 100644
--- a/man2/spu_create.2
+++ b/man2/spu_create.2
@@ -30,7 +30,6 @@ spu_create \- create a new spu context
.B #include <sys/types.h>
.B #include <sys/spu.h>
.PP
-.BI "int spu_create(const char *" pathname ", int " flags ", mode_t " mode ");"
.BI "int spu_create(const char *" pathname ", int " flags ", mode_t " mode ","
.BI " int " neighbor_fd ");"
.fi
@@ -89,6 +88,12 @@ for a full list of the possible
values.
.PP
The
+.I neighbor_fd
+is used only when the
+.B SPU_CREATE_AFFINITY_SPU
+flag is specified; see below.
+.PP
+The
.I flags
argument can be zero or any bitwise OR-ed
combination of the following constants:
@@ -264,6 +269,14 @@ See
.UR http://www.bsc.es\:/projects\:/deepcomputing\:/linuxoncell/
.UE
for the recommended libraries.
+.PP
+Prior to the addition of the
+.B SPU_CREATE_AFFINITY_SPU
+flag in Linux 2.6.23, the
+.BR spu_create ()
+system call took only three arguments (i.e., there was no
+.I neighbor_fd
+argument).
.SH EXAMPLES
See
.BR spu_run (2)
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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