src/tools.rs: implement file_set_contents_full()
This commit is contained in:
Dietmar Maurer
parent
0f778e0652
commit
eea8131952
44
src/tools.rs
44
src/tools.rs
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@ -149,13 +149,25 @@ pub fn file_get_json<P: AsRef<Path>>(path: P, default: Option<Value>) -> Result<
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}).map_err(|err: Error| format_err!("unable to parse json from {:?} - {}", path, err))
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}
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/// Atomically write a file. We first create a temporary file, which
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/// is then renamed.
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/// Atomically write a file
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///
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/// We first create a temporary file, which is then renamed.
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pub fn file_set_contents<P: AsRef<Path>>(
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path: P,
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data: &[u8],
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perm: Option<stat::Mode>,
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) -> Result<(), Error> {
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file_set_contents_full(path, data, perm, None, None)
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}
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/// Atomically write a file with owner and group
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pub fn file_set_contents_full<P: AsRef<Path>>(
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path: P,
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data: &[u8],
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perm: Option<stat::Mode>,
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owner: Option<nix::unistd::Uid>,
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group: Option<nix::unistd::Gid>,
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) -> Result<(), Error> {
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let path = path.as_ref();
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@ -180,6 +192,13 @@ pub fn file_set_contents<P: AsRef<Path>>(
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bail!("fchmod {:?} failed: {}", tmp_path, err);
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}
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if owner != None || group != None {
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if let Err(err) = fchown(fd, owner, group) {
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let _ = unistd::unlink(tmp_path);
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bail!("fchown {:?} failed: {}", tmp_path, err);
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}
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}
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use std::os::unix::io::FromRawFd;
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let mut file = unsafe { File::from_raw_fd(fd) };
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@ -320,7 +339,7 @@ pub fn file_chunker<C, R>(
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Ok(())
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}
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// Returns the Unix uid/gid for the sepcified system user.
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/// Returns the Unix uid/gid for the sepcified system user.
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pub fn getpwnam_ugid(username: &str) -> Result<(libc::uid_t,libc::gid_t), Error> {
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let info = unsafe { libc::getpwnam(std::ffi::CString::new(username).unwrap().as_ptr()) };
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if info == std::ptr::null_mut() {
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@ -332,6 +351,25 @@ pub fn getpwnam_ugid(username: &str) -> Result<(libc::uid_t,libc::gid_t), Error>
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Ok((info.pw_uid, info.pw_gid))
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}
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/// Change ownership of an open file handle
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pub fn fchown(
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fd: RawFd,
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owner: Option<nix::unistd::Uid>,
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group: Option<nix::unistd::Gid>
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) -> Result<(), Error> {
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// According to the POSIX specification, -1 is used to indicate that owner and group
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// are not to be changed. Since uid_t and gid_t are unsigned types, we have to wrap
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// around to get -1 (copied fron nix crate).
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let uid = owner.map(Into::into).unwrap_or((0 as libc::uid_t).wrapping_sub(1));
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let gid = group.map(Into::into).unwrap_or((0 as libc::gid_t).wrapping_sub(1));
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let res = unsafe { libc::fchown(fd, uid, gid) };
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nix::errno::Errno::result(res)?;
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Ok(())
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}
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// Returns the hosts node name (UTS node name)
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pub fn nodename() -> &'static str {
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@ -0,0 +1,185 @@
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use failure::*;
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use std::thread;
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use std::sync::{Arc, Mutex};
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use std::os::unix::io::AsRawFd;
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//use proxmox_backup::tools;
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// fixme: use F_OFD_ locks when implemented with nix::fcntl
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// flock lock conversion is not atomic, so we need to use fcntl
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struct ProcessLocker {
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file: std::fs::File,
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exclusive: bool,
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writers: usize,
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}
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struct SharedLock {
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locker: Arc<Mutex<ProcessLocker>>,
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}
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impl Drop for SharedLock {
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fn drop(&mut self) {
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let tid = std::thread::current().id();
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let pid = std::process::id();
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println!("{:?}:{:?}: Drop Writerlock", pid, tid);
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let mut data = self.locker.lock().unwrap();
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if data.writers == 0 { panic!("unexpected ProcessLocker state"); }
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if data.writers == 1 && !data.exclusive {
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let op = libc::flock {
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l_type: libc::F_UNLCK as i16,
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l_whence: libc::SEEK_SET as i16,
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l_start: 0,
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l_len: 0,
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l_pid: 0,
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};
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if let Err(err) = nix::fcntl::fcntl(data.file.as_raw_fd(), nix::fcntl::FcntlArg::F_SETLKW(&op)) {
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panic!("unable to drop writer lock - {}", err);
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}
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data.writers = 0;
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}
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}
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}
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struct ExclusiveLock {
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locker: Arc<Mutex<ProcessLocker>>,
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}
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impl Drop for ExclusiveLock {
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fn drop(&mut self) {
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let tid = std::thread::current().id();
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let pid = std::process::id();
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println!("{:?}:{:?}: Drop Exclusive lock", pid, tid);
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let mut data = self.locker.lock().unwrap();
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if !data.exclusive { panic!("unexpected ProcessLocker state"); }
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let ltype = if data.writers != 0 { libc::F_RDLCK } else { libc::F_UNLCK };
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let op = libc::flock {
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l_type: ltype as i16,
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l_whence: libc::SEEK_SET as i16,
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l_start: 0,
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l_len: 0,
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l_pid: 0,
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};
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if let Err(err) = nix::fcntl::fcntl(data.file.as_raw_fd(), nix::fcntl::FcntlArg::F_SETLKW(&op)) {
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panic!("unable to drop exclusive lock - {}", err);
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}
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data.exclusive = false;
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}
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}
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impl ProcessLocker {
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pub fn new(lockfile: &str) -> Result<Arc<Mutex<Self>>, Error> {
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let file = std::fs::OpenOptions::new()
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.create(true)
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.read(true)
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.write(true)
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.open(lockfile)?;
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Ok(Arc::new(Mutex::new(Self {
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file: file,
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exclusive: false,
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writers: 0,
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})))
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}
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pub fn try_shared_lock(locker: Arc<Mutex<Self>>) -> Result<SharedLock, Error> {
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let mut data = locker.lock().unwrap();
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if data.writers == 0 && !data.exclusive {
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let op = libc::flock {
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l_type: libc::F_RDLCK as i16,
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l_whence: libc::SEEK_SET as i16,
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l_start: 0,
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l_len: 0,
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l_pid: 0,
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};
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if let Err(err) = nix::fcntl::fcntl(data.file.as_raw_fd(), nix::fcntl::FcntlArg::F_SETLK(&op)) {
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bail!("unable to get shared lock - {}", err);
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}
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}
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data.writers += 1;
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Ok(SharedLock { locker: locker.clone() })
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}
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pub fn try_exclusive_lock(locker: Arc<Mutex<Self>>) -> Result<ExclusiveLock, Error> {
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let mut data = locker.lock().unwrap();
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if data.exclusive {
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bail!("already locked exclusively");
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}
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let op = libc::flock {
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l_type: libc::F_WRLCK as i16,
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l_whence: libc::SEEK_SET as i16,
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l_start: 0,
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l_len: 0,
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l_pid: 0,
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};
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if let Err(err) = nix::fcntl::fcntl(data.file.as_raw_fd(), nix::fcntl::FcntlArg::F_SETLK(&op)) {
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bail!("unable to get exclusive lock - {}", err);
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}
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data.exclusive = true;
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return Ok(ExclusiveLock { locker: locker.clone() });
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}
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}
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fn run_test() -> Result<(), Error>
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{
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let tid = std::thread::current().id();
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let pid = std::process::id();
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let locker = ProcessLocker::new("test.flock")?;
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println!("{:?}:{:?}: try to get shared lock", pid, tid);
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let l1 = ProcessLocker::try_shared_lock(locker.clone())?;
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println!("{:?}:{:?}: got shared lock", pid, tid);
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println!("{:?}:{:?}: try to get exclusive lock", pid, tid);
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let l2 = ProcessLocker::try_exclusive_lock(locker.clone())?;
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println!("{:?}:{:?}: got exclusive lock", pid, tid);
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println!("{:?}:{:?}: try to get shared lock", pid, tid);
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let l3 = ProcessLocker::try_shared_lock(locker.clone())?;
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println!("{:?}:{:?}: got shared lock", pid, tid);
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Ok(())
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}
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fn main() -> Result<(), Error>
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{
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if let Err(err) = run_test() {
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println!("ERROR: {}", err);
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}
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let tid = std::thread::current().id();
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let pid = std::process::id();
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println!("{:?}:{:?}: Exit", pid, tid);
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Ok(())
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}
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@ -0,0 +1,47 @@
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use failure::*;
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use crate::tools;
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use lazy_static::lazy_static;
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use regex::Regex;
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pub struct ProcFsPidStat {
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pub status: u8,
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pub utime: u64,
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pub stime: u64,
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pub starttime: u64,
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pub vsize: u64,
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pub rss: i64,
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}
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pub fn read_proc_pid_stat(pid: nix::unistd::Pid) -> Result<ProcFsPidStat, Error> {
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let statstr = tools::file_read_firstline(format!("/proc/{}/stat", pid))?;
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lazy_static! {
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static ref REGEX: Regex = Regex::new(r"^(?P<pid>\d+) \(?:.*\) (?P<status>\S) -?\d+ -?\d+ -?\d+ -?\d+ -?\d+ \d+ \d+ \d+ \d+ \d+ (?P<utime>\d+) (?P<stime>\d+) -?\d+ -?\d+ -?\d+ -?\d+ -?\d+ 0 (?P<starttime>\d+) (?P<vsize>\d+) (?P<rss>-?\d+) \d+ \d+ \d+ \d+ \d+ \d+ \d+ \d+ \d+ \d+ \d+ \d+ \d+ -?\d+ -?\d+ \d+ \d+ \d+").unwrap();
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}
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if let Some(cap) = REGEX.captures(&statstr) {
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if pid != nix::unistd::Pid::from_raw(cap["pid"].parse::<i32>().unwrap()) {
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bail!("unable to read pid stat for process '{}' - got wrong pid", pid);
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}
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return Ok(ProcFsPidStat {
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status: cap["status"].parse::<u8>().unwrap(),
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utime: cap["utime"].parse::<u64>().unwrap(),
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stime: cap["stime"].parse::<u64>().unwrap(),
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starttime: cap["starttime"].parse::<u64>().unwrap(),
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vsize: cap["vsize"].parse::<u64>().unwrap(),
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rss: cap["rss"].parse::<i64>().unwrap() * 4096,
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});
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}
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bail!("unable to read pid stat for process '{}'", pid);
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}
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pub fn read_proc_starttime(pid: nix::unistd::Pid) -> Result<u64, Error> {
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let info = read_proc_pid_stat(pid)?;
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Ok(info.starttime)
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}
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