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[build] Fix parallel make hang by disabling dotnet build servers #24903

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Merged
dalexsoto merged 1 commit into from
Mar 17, 2026
Merged

[build] Fix parallel make hang by disabling dotnet build servers #24903

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9 changes: 9 additions & 0 deletions Make.config
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Expand Up @@ -403,6 +403,15 @@ DOTNET_DIR=$(abspath $(TOP)/builds/downloads/$(DOTNET_INSTALL_NAME))
export DOTNET_ROOT=$(DOTNET_DIR)
# dotnet now is being looked up in the PATH
export PATH := $(DOTNET_DIR):$(PATH)

# Disable build servers to prevent parallel make from hanging.
# Build servers (MSBuild server, Roslyn/VBCSCompiler) inherit jobserver file
# descriptors from make, and don't close them when daemonizing. This prevents
# make from detecting that all jobs have finished, causing it to hang
# indefinitely at the end of the build.
export DOTNET_CLI_USE_MSBUILD_SERVER=0
export UseSharedCompilation=false
export MSBUILDDISABLENODEREUSE=1
DOTNET=$(DOTNET_DIR)/dotnet
DOTNET_BCL_DIR:=$(abspath $(TOP)/packages/microsoft.netcore.app.ref/$(DOTNET_BCL_VERSION)/ref/$(DOTNET_TFM))
# when bumping to a new .NET version, there may be a period when some parts of .NET is still on the old .NET version, so handle that here for DOTNET_BCL_DIR
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5 changes: 2 additions & 3 deletions Makefile
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Expand Up @@ -32,6 +32,8 @@ world: check-system
@$(MAKE) reset-versions
@$(MAKE) all -j8
@$(MAKE) install -j8
@echo "Build is done, the following workloads were built:"
@$(DOTNET) workload list

.PHONY: check-system
check-system:
Expand Down Expand Up @@ -68,9 +70,6 @@ install-hook::
exit 1; \
fi

all-hook install-hook::
$(Q) $(MAKE) -C dotnet shutdown-build-server

dotnet-install-system:
$(Q) $(MAKE) -C dotnet install-system

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20 changes: 0 additions & 20 deletions dotnet/Makefile
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Expand Up @@ -536,23 +536,3 @@ clean-local::
$(Q) $(DOTNET) restore package/workaround-for-maccore-issue-2427/restore.csproj /bl:package/workaround-for-maccore-issue-2427/restore.binlog $(MSBUILD_VERBOSITY)
$(Q) touch $@

# We need to shut down the builder server, because:
# We're using parallel make, and parallel make will start a jobserver, managed by file descriptors, where these file descriptors must be closed in all subprocesses for make to realize it's done.
# 'dotnet pack' might have started a build server
# The build server does not close any file descriptors it may have inherited when daemonizing itself.
# Thus the build server (which will still be alive after we're done building here) might have a file descriptor open which make is waiting for.
# The proper fix is to fix the build server to close its file descriptors.
# The intermediate working is to shut down the build server instead. An alternative solution would be to pass /p:UseSharedCompilation=false to 'dotnet pack' to disable the usage of the build server.
#
# The 'shutdown-build-server' is executed in a sub-make (and not as a dependency to the all-hook target),
# to make sure it's executed after everything else is built in this file.
all-hook::
$(Q) $(MAKE) shutdown-build-server

shutdown-build-server:
$(Q) echo "Shutting down build servers:"
$(Q) $(DOTNET) build-server shutdown | sed 's/^/ /' || true
$(Q) echo "Listing .NET processes still alive:"
$(Q) pgrep -lf "^$(DOTNET)" | sed 's/^/ /' || true
$(Q) echo "Killing the above mentioned processes."
$(Q) pkill -9 -f "^$(DOTNET)" | sed 's/^/ /' || true
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