mirror of
https://github.com/Homebrew/brew.git
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76 lines
2.7 KiB
Bash
76 lines
2.7 KiB
Bash
# Create a lock using `flock(2)`. A command name with arguments is required as
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# first argument. The lock will be automatically unlocked when the shell process
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# quits. Note due to the fixed FD, a shell process can only create one lock.
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# HOMEBREW_LIBRARY is by brew.sh
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# HOMEBREW_PREFIX is set by extend/ENV/super.rb
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# shellcheck disable=SC2154
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lock() {
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local command_name_and_args="$1"
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# use bash to replace spaces with dashes
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local lock_filename="${command_name_and_args// /-}"
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local lock_dir="${HOMEBREW_PREFIX}/var/homebrew/locks"
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local lock_file="${lock_dir}/${lock_filename}"
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[[ -d "${lock_dir}" ]] || mkdir -p "${lock_dir}"
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if [[ ! -w "${lock_dir}" ]]
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then
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odie <<EOS
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Can't create \`brew ${command_name_and_args}\` lock in ${lock_dir}!
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Fix permissions by running:
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sudo chown -R ${USER-\$(whoami)} ${HOMEBREW_PREFIX}/var/homebrew
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EOS
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fi
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# 200 is the file descriptor (FD) used in the lock.
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# This FD should be used exclusively for lock purpose.
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# Any value except 0(stdin), 1(stdout) and 2(stderr) can do the job.
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# Noted, FD is unique per process but it will be shared to subprocess.
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# It is recommended to choose a large number to avoid conflicting with
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# other FD opened by the script.
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#
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# close FD first, this is required if parent process holds a different lock.
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exec 200>&-
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# open the lock file to FD, so the shell process can hold the lock.
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exec 200>"${lock_file}"
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if ! _create_lock 200 "${command_name_and_args}"
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then
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local lock_context
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if [[ -n "${HOMEBREW_LOCK_CONTEXT}" ]]
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then
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lock_context="\n${HOMEBREW_LOCK_CONTEXT}"
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fi
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odie <<EOS
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Another \`brew ${command_name_and_args}\` process is already running.${lock_context}
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Please wait for it to finish or terminate it to continue.
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EOS
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fi
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}
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_create_lock() {
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local lock_file_descriptor="$1"
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local command_name_and_args="$2"
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local ruby="/usr/bin/ruby"
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local python="/usr/bin/python"
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[[ -x "${ruby}" ]] || ruby="$(type -P ruby)"
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[[ -x "${python}" ]] || python="$(type -P python)"
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local utils_lock_sh="${HOMEBREW_LIBRARY}/Homebrew/utils/lock_sh"
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local oldest_ruby_with_flock="1.8.7"
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if [[ -x "$(type -P lockf)" ]]
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then
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lockf -t 0 "${lock_file_descriptor}"
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elif [[ -x "$(type -P flock)" ]]
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then
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flock -n "${lock_file_descriptor}"
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elif [[ -x "${ruby}" ]] && "${ruby}" "${utils_lock_sh}/ruby_check_version.rb" "${oldest_ruby_with_flock}"
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then
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"${ruby}" "${utils_lock_sh}/ruby_lock_file_descriptor.rb" "${lock_file_descriptor}"
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elif [[ -x "${python}" ]]
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then
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"${python}" -c "import fcntl; fcntl.flock(${lock_file_descriptor}, fcntl.LOCK_EX | fcntl.LOCK_NB)"
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else
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onoe "Cannot create \`brew ${command_name_and_args}\` lock due to missing/too old ruby/flock/python, please avoid running Homebrew in parallel."
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fi
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}
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