63 lines
2.2 KiB
Bash
63 lines
2.2 KiB
Bash
# create a lock using `flock(2)`. A name is required as first argument.
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# the lock will be automatically unlocked when the shell process quits.
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# Noted due to the fixed FD, a shell process can only create one lock.
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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 name="$1"
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local lock_dir="${HOMEBREW_PREFIX}/var/homebrew/locks"
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local lock_file="${lock_dir}/${name}"
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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 ${name} lock in ${lock_dir}!
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Fix permissions by running:
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sudo chown -R ${USER-\$(whoami)} ${HOMEBREW_PREFIX}/var/homebrew
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EOS
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fi
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# 200 is the file descriptor used in the lock.
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# This FD should be used exclusively for lock purpose.
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# Any value except 0(stdin), 1(stdout) and 2(stderr) can do the job.
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# Noted, FD is unique per process but it will be shared to subprocess.
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# It is recommended to choose a large number to avoid conflicting with
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# other FD opened by the script.
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#
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# close FD first, this is required if parent process holds a different lock.
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exec 200>&-
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# open the lock file to FD, so the shell process can hold the lock.
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exec 200>"${lock_file}"
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if ! _create_lock 200 "${name}"
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then
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odie <<EOS
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Another active Homebrew ${name} process is already in progress.
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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_fd="$1"
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local name="$2"
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local ruby="/usr/bin/ruby"
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local python="/usr/bin/python"
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[[ -x "${ruby}" ]] || ruby="$(type -P ruby)"
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[[ -x "${python}" ]] || python="$(type -P python)"
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# Use /dev/stdin, otherwise Ruby can error if uid != euid.
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# Can't use "-" as that's also blocked:
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# https://github.com/ruby/ruby/blob/e51435177e88fc845528dff7cf2bc2b75dd36144/ruby.c#L2333-L2335
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if [[ -x "${ruby}" ]] && "${ruby}" /dev/stdin <<<"exit(RUBY_VERSION >= '1.8.7')"
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then
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"${ruby}" /dev/stdin <<<"File.new(${lock_fd}).flock(File::LOCK_EX | File::LOCK_NB) || exit(1)"
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elif [[ -x "${python}" ]]
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then
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"${python}" -c "import fcntl; fcntl.flock(${lock_fd}, fcntl.LOCK_EX | fcntl.LOCK_NB)"
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elif [[ -x "$(type -P flock)" ]]
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then
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flock -n "${lock_fd}"
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else
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onoe "Cannot create ${name} lock, please avoid running Homebrew in parallel."
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fi
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}
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