Fix tests and a thread safety bug

README.md

@@ -42,7 +42,7 @@ git commit --no-verify
 ### Hardware tests
 The MMC tests are ignored by default as they require a CD/DVD drive.
 ```sh
-cargo test -- --include-ignored
+cargo test --all-features -- --include-ignored
 ```
 
 A few of the tests require manual intervention (such as media
@@ -51,7 +51,7 @@ These are located in [`tests/`](./tests).
 
 Example, to run the media removal test:
 ```sh
-MANUAL_TESTS=1 cargo test -- media_removal --include-ignored
+MANUAL_TESTS=1 cargo test --all-features -- media_removal --include-ignored
 ```
 
 ## See also

src/cdio.rs

@@ -48,7 +48,7 @@ impl Cdio {
 
         // SAFETY: This invokes cdio_init(), which mutates a static variable.
         // CDIO_LAST_DRIVER_LOCK is held to prevent data races.
-        let _lock = CDIO_LAST_DRIVER_LOCK.lock().unwrap();
+        let _lock = CDIO_INIT_LOCK.lock().unwrap();
         return unsafe { libcdio_sys::cdio_open_am(source, driver, access_mode) };
 
         /// Although prefixed "MMC", this does imply read-write for all
@@ -67,15 +67,19 @@ impl Deref for Cdio {
 
 impl Drop for Cdio {
     fn drop(&mut self) {
-        let _lock = CDIO_LAST_DRIVER_LOCK.lock().unwrap();
+        let _lock = CDIO_INIT_LOCK.lock().unwrap();
 
         // SAFETY: This method invokes modifies a static variable.
         // CDIO_LAST_DRIVER_LOCK is held to prevent data races.
         unsafe { libcdio_sys::cdio_destroy(self.cdio.as_ptr()) }
     }
 }
 
-/// A lock guarding a private static named `CdIo_last_driver`. It must be held
-/// before invoking any libcdio methods that modify this value.
-/// As of libcdio v2.3.0, such methods are `cdio_init()` and `cdio_destroy()`.
-static CDIO_LAST_DRIVER_LOCK: Mutex<()> = Mutex::new(());
+/// A lock that must be held before any routine that initializes or
+/// destroys `CdIo_t`.
+/// It was found that the GNU/Linux driver initialization routine,
+/// is NOT thread safe as of libcdio v2.4.0.
+/// Apart from that, this also guards the use of a private static
+/// named `CdIo_last_driver`, used by `CdIo_t` during init
+/// and cleanup.
+pub(crate) static CDIO_INIT_LOCK: Mutex<()> = Mutex::new(());

src/drive.rs

@@ -29,7 +29,10 @@ use bitflags::bitflags;
 use libcdio_sys::cdio_hwinfo_t;
 use thiserror::Error;
 
-use crate::cdio::Cdio;
+use crate::{
+    cdio::{CDIO_INIT_LOCK, Cdio},
+    logging,
+};
 
 /// An interface to a disc drive.
 pub struct Drive {
@@ -39,6 +42,12 @@ pub struct Drive {
 impl Drive {
     /// Returns a list of connected drives.
     pub fn drives() -> Vec<PathBuf> {
+        logging::init_logger();
+
+        // SAFETY: This method internally initializes an instance of CdIo_t,
+        // which is not thread safe. Hold CDIO_INIT_LOCK to uphold thread
+        // safety.
+        let _lock = CDIO_INIT_LOCK.lock().unwrap();
         let drive_list =
             unsafe { libcdio_sys::cdio_get_devices(libcdio_sys::driver_id_t_DRIVER_DEVICE) };
         if drive_list.is_null() {

tests/media_removal.rs

@@ -1,12 +1,14 @@
 //! Tests that would remove the drive media
-use libcdio_rs::{
-    Mmc,
-    mmc::{MmcCloseTrayError, MmcError, MmcSenseData, MmcStartStopError, SenseKey},
-};
 
+#[cfg(feature = "mmc")]
 #[test]
 #[ignore = "requires a drive with mmc"]
 fn media_removal() {
+    use libcdio_rs::{
+        Mmc,
+        mmc::{MmcCloseTrayError, MmcError, MmcSenseData, MmcStartStopError, SenseKey},
+    };
+
     if std::env::var("MANUAL_TESTS").is_err() {
         return;
     }