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

* [PATCH] arm/scp-firmware: fix build race
@ 2020-09-14 18:19 Ross Burton
  2020-09-21 14:24 ` [meta-arm] " Jon Mason
  0 siblings, 1 reply; 2+ messages in thread
From: Ross Burton @ 2020-09-14 18:19 UTC (permalink / raw)
  To: meta-arm

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

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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