wrap UnsafeCell<MmapMut> with a mutex to fix Clippy lint on master

Cargo.toml

@@ -24,6 +24,7 @@ fs4 = "0.6"
 # to use direct functions on FreeBSD
 rustix = { version = "0", features = [ "fs" ]}
 crossbeam-channel = "0.5"
+parking_lot = { version = "0.12.1" }
 
 # Binary dependencies
 docopt = "1.1"
@@ -35,4 +36,4 @@ hdrhistogram = "7.5.2"
 quickcheck = "1.0.3"
 regex = "1.8.1"
 tempfile = "3.5.0"
-chrono = "0.4.24"
+chrono = "0.4.31"

examples/bench.rs

@@ -42,7 +42,7 @@ fn main() {
 }
 
 pub fn precise_time_ns() -> u64 {
-    chrono::offset::Utc::now().timestamp_nanos() as u64
+    chrono::offset::Utc::now().timestamp_nanos_opt().unwrap() as u64
 }
 
 fn format_duration(n: u64) -> String {

src/mmap_view_sync.rs

@@ -1,4 +1,5 @@
 use memmap2::{MmapMut, MmapOptions};
+use parking_lot::Mutex;
 use std::cell::UnsafeCell;
 use std::fmt;
 use std::fs::File;
@@ -13,7 +14,7 @@ use std::sync::Arc;
 /// The view may be split into disjoint ranges, each of which will share the
 /// underlying memory map.
 pub struct MmapViewSync {
-    inner: Arc<UnsafeCell<MmapMut>>,
+    inner: Arc<Mutex<UnsafeCell<MmapMut>>>,
     offset: usize,
     len: usize,
 }
@@ -87,15 +88,15 @@ impl MmapViewSync {
     ///
     /// The caller must ensure that memory outside the `offset`/`len` range is not accessed.
     fn inner(&self) -> &MmapMut {
-        unsafe { &*self.inner.get() }
+        unsafe { &*self.inner.lock().get() }
     }
 
     /// Get a mutable reference to the inner mmap.
     ///
     /// The caller must ensure that memory outside the `offset`/`len` range is not accessed.
     #[allow(clippy::mut_from_ref)]
     fn inner_mut(&self) -> &mut MmapMut {
-        unsafe { &mut *self.inner.get() }
+        unsafe { &mut *self.inner.lock().get() }
     }
 
     /// Flushes outstanding view modifications to disk.
@@ -147,7 +148,7 @@ impl From<MmapMut> for MmapViewSync {
     fn from(mmap: MmapMut) -> MmapViewSync {
         let len = mmap.len();
         MmapViewSync {
-            inner: Arc::new(UnsafeCell::new(mmap)),
+            inner: Arc::new(Mutex::new(UnsafeCell::new(mmap))),
             offset: 0,
             len,
         }