[meta-arm] arm/scp-firmware: fix build race

Backport a patch to fix a race in parallel builds.

Change-Id: I4b33b819f2da302369ca77429f25d5c15672c5f3
Signed-off-by: Ross Burton <ross.burton@arm.com>
---
 ..._code-atomically-rewrite-the-generat.patch | 69 +++++++++++++++++++
 .../scp-firmware/scp-firmware_2.6.0.bb        |  3 +-
 2 files changed, 71 insertions(+), 1 deletion(-)
 create mode 100644 meta-arm/recipes-bsp/scp-firmware/files/0001-tools-gen_module_code-atomically-rewrite-the-generat.patch

On Mon, Sep 14, 2020 at 07:19:03PM +0100, Ross Burton wrote:
> Backport a patch to fix a race in parallel builds.
> 
> Change-Id: I4b33b819f2da302369ca77429f25d5c15672c5f3
> Signed-off-by: Ross Burton <ross.burton@arm.com>

Pulled into master.

Thanks,
Jon

> ---
>  ..._code-atomically-rewrite-the-generat.patch | 69 +++++++++++++++++++
>  .../scp-firmware/scp-firmware_2.6.0.bb        |  3 +-
>  2 files changed, 71 insertions(+), 1 deletion(-)
>  create mode 100644 meta-arm/recipes-bsp/scp-firmware/files/0001-tools-gen_module_code-atomically-rewrite-the-generat.patch
> 
> diff --git a/meta-arm/recipes-bsp/scp-firmware/files/0001-tools-gen_module_code-atomically-rewrite-the-generat.patch b/meta-arm/recipes-bsp/scp-firmware/files/0001-tools-gen_module_code-atomically-rewrite-the-generat.patch
> new file mode 100644
> index 0000000..05bb025
> --- /dev/null
> +++ b/meta-arm/recipes-bsp/scp-firmware/files/0001-tools-gen_module_code-atomically-rewrite-the-generat.patch
> @@ -0,0 +1,69 @@
> +Upstream-Status: Backport
> +Signed-off-by: Ross Burton <ross.burton@arm.com>
> +
> +From 34e1c04534607f5605255f39fb46e26261fc9c4e Mon Sep 17 00:00:00 2001
> +From: Ross Burton <ross.burton@arm.com>
> +Date: Tue, 8 Sep 2020 11:49:08 +0100
> +Subject: [PATCH] tools/gen_module_code: atomically rewrite the generated files
> +
> +The gen_module rule in rules.mk is marked as .PHONY, so make will
> +execute it whenever it is mentioned. This results in gen_module_code
> +being executed 64 times for a Juno build.
> +
> +However in heavily parallel builds there's a good chance that
> +gen_module_code is writing a file whilst the compiler is reading it
> +because make also doesn't know what files are generated by
> +gen_module_code.
> +
> +The correct fix is to adjust the Makefiles so that the dependencies are
> +correct but this isn't trivial, so band-aid the problem by atomically
> +writing the generated files.
> +
> +Change-Id: I82d44f9ea6537a91002e1f80de8861d208571630
> +Signed-off-by: Ross Burton <ross.burton@arm.com>
> +---
> + tools/gen_module_code.py | 19 ++++++++++++++-----
> + 1 file changed, 14 insertions(+), 5 deletions(-)
> +
> +diff --git a/tools/gen_module_code.py b/tools/gen_module_code.py
> +index 7b395384..ee099b71 100755
> +--- a/tools/gen_module_code.py
> ++++ b/tools/gen_module_code.py
> +@@ -17,6 +17,7 @@
> + import argparse
> + import os
> + import sys
> ++import tempfile
> + 
> + DEFAULT_PATH = 'build/'
> + 
> +@@ -53,13 +54,21 @@ TEMPLATE_C = "/* This file was auto generated using {} */\n" \
> + 
> + def generate_file(path, filename, content):
> +     full_filename = os.path.join(path, filename)
> +-    with open(full_filename, 'a+') as f:
> +-        f.seek(0)
> +-        if f.read() != content:
> ++
> ++    try:
> ++        with open(full_filename) as f:
> ++            rewrite = f.read() != content
> ++    except FileNotFoundError:
> ++        rewrite = True
> ++
> ++    if rewrite:
> ++        with tempfile.NamedTemporaryFile(prefix="gen-module-code",
> ++                                         dir=path,
> ++                                         delete=False,
> ++                                         mode="wt") as f:
> +             print("[GEN] {}...".format(full_filename))
> +-            f.seek(0)
> +-            f.truncate()
> +             f.write(content)
> ++        os.replace(f.name, full_filename)
> + 
> + 
> + def generate_header(path, modules):
> +-- 
> +2.28.0
> +
> diff --git a/meta-arm/recipes-bsp/scp-firmware/scp-firmware_2.6.0.bb b/meta-arm/recipes-bsp/scp-firmware/scp-firmware_2.6.0.bb
> index 4de0912..f9510e4 100644
> --- a/meta-arm/recipes-bsp/scp-firmware/scp-firmware_2.6.0.bb
> +++ b/meta-arm/recipes-bsp/scp-firmware/scp-firmware_2.6.0.bb
> @@ -6,7 +6,8 @@ LICENSE = "BSD-3-Clause & Apache-2.0"
>  LIC_FILES_CHKSUM = "file://license.md;beginline=5;md5=9db9e3d2fb8d9300a6c3d15101b19731 \
>                      file://cmsis/LICENSE.txt;md5=e3fc50a88d0a364313df4b21ef20c29e"
>  
> -SRC_URI = "gitsm://github.com/ARM-software/SCP-firmware.git;protocol=https"
> +SRC_URI = "gitsm://github.com/ARM-software/SCP-firmware.git;protocol=https \
> +           file://0001-tools-gen_module_code-atomically-rewrite-the-generat.patch"
>  SRCREV  = "db19910aca6d1032eb0329e5fbb70a92b997f6f2"
>  
>  PROVIDES += "virtual/control-processor-firmware"
> -- 
> 2.28.0
> 

>
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