diff --git a/examples/Cargo.toml b/examples/Cargo.toml
index d95a32d036d..5fa4f7438c5 100644
--- a/examples/Cargo.toml
+++ b/examples/Cargo.toml
@@ -10,7 +10,7 @@ edition = "2018"
 tokio = { version = "0.3.0", path = "../tokio", features = ["full", "tracing"] }
 tracing = "0.1"
 tracing-subscriber = { version = "0.2.7", default-features = false, features = ["fmt", "ansi", "env-filter", "chrono", "tracing-log"] }
-tokio-util = { version = "0.4.0", path = "../tokio-util", features = ["full"] }
+tokio-util = { version = "0.5.0", path = "../tokio-util", features = ["full"] }
 bytes = "0.6"
 futures = "0.3.0"
 http = "0.2"
diff --git a/tokio-util/CHANGELOG.md b/tokio-util/CHANGELOG.md
index e9aa0bac747..48dfe778e26 100644
--- a/tokio-util/CHANGELOG.md
+++ b/tokio-util/CHANGELOG.md
@@ -1,3 +1,11 @@
+### Added
+- io: `poll_read_buf` util fn (#2972).
+
+# 0.5.0 (October 30, 2020)
+
+### Changed
+- io: update `bytes` to 0.6 (#3071).
+
 # 0.4.0 (October 15, 2020)
 
 ### Added
diff --git a/tokio-util/Cargo.toml b/tokio-util/Cargo.toml
index c1b2ee66db4..ba2f3a4f1f6 100644
--- a/tokio-util/Cargo.toml
+++ b/tokio-util/Cargo.toml
@@ -7,13 +7,13 @@ name = "tokio-util"
 #   - Cargo.toml
 # - Update CHANGELOG.md.
 # - Create "v0.2.x" git tag.
-version = "0.4.0"
+version = "0.5.0"
 edition = "2018"
 authors = ["Tokio Contributors <team@tokio.rs>"]
 license = "MIT"
 repository = "https://github.com/tokio-rs/tokio"
 homepage = "https://tokio.rs"
-documentation = "https://docs.rs/tokio-util/0.4.0/tokio_util"
+documentation = "https://docs.rs/tokio-util/0.5.0/tokio_util"
 description = """
 Additional utilities for working with Tokio.
 """
diff --git a/tokio-util/src/codec/framed_impl.rs b/tokio-util/src/codec/framed_impl.rs
index c161808f66e..e8b29999e10 100644
--- a/tokio-util/src/codec/framed_impl.rs
+++ b/tokio-util/src/codec/framed_impl.rs
@@ -150,7 +150,7 @@ where
             // got room for at least one byte to read to ensure that we don't
             // get a spurious 0 that looks like EOF
             state.buffer.reserve(1);
-            let bytect = match poll_read_buf(cx, pinned.inner.as_mut(), &mut state.buffer)? {
+            let bytect = match poll_read_buf(pinned.inner.as_mut(), cx, &mut state.buffer)? {
                 Poll::Ready(ct) => ct,
                 Poll::Pending => return Poll::Pending,
             };
diff --git a/tokio-util/src/io/mod.rs b/tokio-util/src/io/mod.rs
index 6f181ab1703..eefd65a5e83 100644
--- a/tokio-util/src/io/mod.rs
+++ b/tokio-util/src/io/mod.rs
@@ -13,3 +13,4 @@ mod stream_reader;
 pub use self::read_buf::read_buf;
 pub use self::reader_stream::ReaderStream;
 pub use self::stream_reader::StreamReader;
+pub use crate::util::poll_read_buf;
diff --git a/tokio-util/src/io/read_buf.rs b/tokio-util/src/io/read_buf.rs
index 5bc0d5866f4..cc3c505f934 100644
--- a/tokio-util/src/io/read_buf.rs
+++ b/tokio-util/src/io/read_buf.rs
@@ -59,7 +59,7 @@ where
 
         fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
             let this = &mut *self;
-            crate::util::poll_read_buf(cx, Pin::new(this.0), this.1)
+            crate::util::poll_read_buf(Pin::new(this.0), cx, this.1)
         }
     }
 }
diff --git a/tokio-util/src/io/reader_stream.rs b/tokio-util/src/io/reader_stream.rs
index ab0c22fba73..3e6a05eff4d 100644
--- a/tokio-util/src/io/reader_stream.rs
+++ b/tokio-util/src/io/reader_stream.rs
@@ -83,7 +83,7 @@ impl<R: AsyncRead> Stream for ReaderStream<R> {
             this.buf.reserve(CAPACITY);
         }
 
-        match poll_read_buf(cx, reader, &mut this.buf) {
+        match poll_read_buf(reader, cx, &mut this.buf) {
             Poll::Pending => Poll::Pending,
             Poll::Ready(Err(err)) => {
                 self.project().reader.set(None);
diff --git a/tokio-util/src/lib.rs b/tokio-util/src/lib.rs
index f4cf94704ad..09dd5a1071c 100644
--- a/tokio-util/src/lib.rs
+++ b/tokio-util/src/lib.rs
@@ -1,4 +1,4 @@
-#![doc(html_root_url = "https://docs.rs/tokio-util/0.4.0")]
+#![doc(html_root_url = "https://docs.rs/tokio-util/0.5.0")]
 #![allow(clippy::needless_doctest_main)]
 #![warn(
     missing_debug_implementations,
@@ -69,10 +69,49 @@ mod util {
     use std::pin::Pin;
     use std::task::{Context, Poll};
 
-    pub(crate) fn poll_read_buf<T: AsyncRead>(
-        cx: &mut Context<'_>,
+    /// Try to read data from an `AsyncRead` into an implementer of the [`Buf`] trait.
+    ///
+    /// [`Buf`]: bytes::Buf
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use bytes::{Bytes, BytesMut};
+    /// use tokio::stream;
+    /// use tokio::io::Result;
+    /// use tokio_util::io::{StreamReader, poll_read_buf};
+    /// use futures::future::poll_fn;
+    /// use std::pin::Pin;
+    /// # #[tokio::main]
+    /// # async fn main() -> std::io::Result<()> {
+    ///
+    /// // Create a reader from an iterator. This particular reader will always be
+    /// // ready.
+    /// let mut read = StreamReader::new(stream::iter(vec![Result::Ok(Bytes::from_static(&[0, 1, 2, 3]))]));
+    ///
+    /// let mut buf = BytesMut::new();
+    /// let mut reads = 0;
+    ///
+    /// loop {
+    ///     reads += 1;
+    ///     let n = poll_fn(|cx| poll_read_buf(Pin::new(&mut read), cx, &mut buf)).await?;
+    ///
+    ///     if n == 0 {
+    ///         break;
+    ///     }
+    /// }
+    ///
+    /// // one or more reads might be necessary.
+    /// assert!(reads >= 1);
+    /// assert_eq!(&buf[..], &[0, 1, 2, 3]);
+    /// # Ok(())
+    /// # }
+    /// ```
+    #[cfg_attr(not(feature = "io"), allow(unreachable_pub))]
+    pub fn poll_read_buf<T: AsyncRead, B: BufMut>(
         io: Pin<&mut T>,
-        buf: &mut impl BufMut,
+        cx: &mut Context<'_>,
+        buf: &mut B,
     ) -> Poll<io::Result<usize>> {
         if !buf.has_remaining_mut() {
             return Poll::Ready(Ok(0));
diff --git a/tokio/Cargo.toml b/tokio/Cargo.toml
index 6c5de90ddc2..c4825c20650 100644
--- a/tokio/Cargo.toml
+++ b/tokio/Cargo.toml
@@ -102,7 +102,7 @@ mio = { version = "0.7.3", optional = true }
 num_cpus = { version = "1.8.0", optional = true }
 parking_lot = { version = "0.11.0", optional = true } # Not in full
 slab = { version = "0.4.1", optional = true }
-tracing = { version = "0.1.16", default-features = false, features = ["std"], optional = true } # Not in full
+tracing = { version = "0.1.21", default-features = false, features = ["std"], optional = true } # Not in full
 
 [target.'cfg(unix)'.dependencies]
 libc = { version = "0.2.42", optional = true }
@@ -126,9 +126,12 @@ tempfile = "3.1.0"
 [target.'cfg(loom)'.dev-dependencies]
 loom = { version = "0.3.5", features = ["futures", "checkpoint"] }
 
+[build-dependencies]
+autocfg = "1" # Needed for conditionally enabling `track-caller`
+
 [package.metadata.docs.rs]
 all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
 
 [package.metadata.playground]
-features = ["full"]
+features = ["full"]
\ No newline at end of file
diff --git a/tokio/build.rs b/tokio/build.rs
new file mode 100644
index 00000000000..fe5c8300560
--- /dev/null
+++ b/tokio/build.rs
@@ -0,0 +1,22 @@
+use autocfg::AutoCfg;
+
+fn main() {
+    match AutoCfg::new() {
+        Ok(ac) => {
+            // The #[track_caller] attribute was stabilized in rustc 1.46.0.
+            if ac.probe_rustc_version(1, 46) {
+                autocfg::emit("tokio_track_caller")
+            }
+        }
+
+        Err(e) => {
+            // If we couldn't detect the compiler version and features, just
+            // print a warning. This isn't a fatal error: we can still build
+            // Tokio, we just can't enable cfgs automatically.
+            println!(
+                "cargo:warning=tokio: failed to detect compiler features: {}",
+                e
+            );
+        }
+    }
+}
diff --git a/tokio/src/net/unix/ucred.rs b/tokio/src/net/unix/ucred.rs
index ef214a702fa..7d73ee02ebb 100644
--- a/tokio/src/net/unix/ucred.rs
+++ b/tokio/src/net/unix/ucred.rs
@@ -1,8 +1,10 @@
-use libc::{gid_t, uid_t};
+use libc::{gid_t, pid_t, uid_t};
 
 /// Credentials of a process
 #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
 pub struct UCred {
+    /// PID (process ID) of the process
+    pid: Option<pid_t>,
     /// UID (user ID) of the process
     uid: uid_t,
     /// GID (group ID) of the process
@@ -19,6 +21,13 @@ impl UCred {
     pub fn gid(&self) -> gid_t {
         self.gid
     }
+
+    /// Gets PID (process ID) of the process.
+    ///
+    /// This is only implemented under linux, android, IOS and MacOS
+    pub fn pid(&self) -> Option<pid_t> {
+        self.pid
+    }
 }
 
 #[cfg(any(target_os = "linux", target_os = "android"))]
@@ -26,12 +35,13 @@ pub(crate) use self::impl_linux::get_peer_cred;
 
 #[cfg(any(
     target_os = "dragonfly",
-    target_os = "macos",
-    target_os = "ios",
     target_os = "freebsd",
     target_os = "netbsd",
     target_os = "openbsd"
 ))]
+pub(crate) use self::impl_bsd::get_peer_cred;
+
+#[cfg(any(target_os = "macos", target_os = "ios"))]
 pub(crate) use self::impl_macos::get_peer_cred;
 
 #[cfg(any(target_os = "solaris", target_os = "illumos"))]
@@ -77,6 +87,7 @@ pub(crate) mod impl_linux {
                 Ok(super::UCred {
                     uid: ucred.uid,
                     gid: ucred.gid,
+                    pid: Some(ucred.pid),
                 })
             } else {
                 Err(io::Error::last_os_error())
@@ -87,13 +98,11 @@ pub(crate) mod impl_linux {
 
 #[cfg(any(
     target_os = "dragonfly",
-    target_os = "macos",
-    target_os = "ios",
     target_os = "freebsd",
     target_os = "netbsd",
     target_os = "openbsd"
 ))]
-pub(crate) mod impl_macos {
+pub(crate) mod impl_bsd {
     use crate::net::unix::UnixStream;
 
     use libc::getpeereid;
@@ -114,6 +123,54 @@ pub(crate) mod impl_macos {
                 Ok(super::UCred {
                     uid: uid.assume_init(),
                     gid: gid.assume_init(),
+                    pid: None,
+                })
+            } else {
+                Err(io::Error::last_os_error())
+            }
+        }
+    }
+}
+
+#[cfg(any(target_os = "macos", target_os = "ios"))]
+pub(crate) mod impl_macos {
+    use crate::net::unix::UnixStream;
+
+    use libc::{c_void, getpeereid, getsockopt, pid_t, LOCAL_PEEREPID, SOL_LOCAL};
+    use std::io;
+    use std::mem::size_of;
+    use std::mem::MaybeUninit;
+    use std::os::unix::io::AsRawFd;
+
+    pub(crate) fn get_peer_cred(sock: &UnixStream) -> io::Result<super::UCred> {
+        unsafe {
+            let raw_fd = sock.as_raw_fd();
+
+            let mut uid = MaybeUninit::uninit();
+            let mut gid = MaybeUninit::uninit();
+            let mut pid: MaybeUninit<pid_t> = MaybeUninit::uninit();
+            let mut pid_size: MaybeUninit<u32> = MaybeUninit::new(size_of::<pid_t>() as u32);
+
+            if getsockopt(
+                raw_fd,
+                SOL_LOCAL,
+                LOCAL_PEEREPID,
+                pid.as_mut_ptr() as *mut c_void,
+                pid_size.as_mut_ptr(),
+            ) != 0
+            {
+                return Err(io::Error::last_os_error());
+            }
+
+            assert!(pid_size.assume_init() == (size_of::<pid_t>() as u32));
+
+            let ret = getpeereid(raw_fd, uid.as_mut_ptr(), gid.as_mut_ptr());
+
+            if ret == 0 {
+                Ok(super::UCred {
+                    uid: uid.assume_init(),
+                    gid: gid.assume_init(),
+                    pid: Some(pid.assume_init()),
                 })
             } else {
                 Err(io::Error::last_os_error())
@@ -154,7 +211,11 @@ pub(crate) mod impl_solaris {
 
                 ucred_free(cred);
 
-                Ok(super::UCred { uid, gid })
+                Ok(super::UCred {
+                    uid,
+                    gid,
+                    pid: None,
+                })
             } else {
                 Err(io::Error::last_os_error())
             }
diff --git a/tokio/src/runtime/handle.rs b/tokio/src/runtime/handle.rs
index d2a69a24ceb..bce5d07d17d 100644
--- a/tokio/src/runtime/handle.rs
+++ b/tokio/src/runtime/handle.rs
@@ -125,15 +125,19 @@ impl Handle {
     /// });
     /// # }
     /// ```
+    #[cfg_attr(tokio_track_caller, track_caller)]
     pub fn spawn<F>(&self, future: F) -> JoinHandle<F::Output>
     where
         F: Future + Send + 'static,
         F::Output: Send + 'static,
     {
+        #[cfg(feature = "tracing")]
+        let future = crate::util::trace::task(future, "task");
         self.spawner.spawn(future)
     }
 
-    /// Run the provided function on an executor dedicated to blocking operations.
+    /// Run the provided function on an executor dedicated to blocking
+    /// operations.
     ///
     /// # Examples
     ///
@@ -151,12 +155,24 @@ impl Handle {
     ///     println!("now running on a worker thread");
     /// });
     /// # }
+    #[cfg_attr(tokio_track_caller, track_caller)]
     pub fn spawn_blocking<F, R>(&self, func: F) -> JoinHandle<R>
     where
         F: FnOnce() -> R + Send + 'static,
     {
         #[cfg(feature = "tracing")]
         let func = {
+            #[cfg(tokio_track_caller)]
+            let location = std::panic::Location::caller();
+            #[cfg(tokio_track_caller)]
+            let span = tracing::trace_span!(
+                target: "tokio::task",
+                "task",
+                kind = %"blocking",
+                function = %std::any::type_name::<F>(),
+                spawn.location = %format_args!("{}:{}:{}", location.file(), location.line(), location.column()),
+            );
+            #[cfg(not(tokio_track_caller))]
             let span = tracing::trace_span!(
                 target: "tokio::task",
                 "task",
diff --git a/tokio/src/runtime/mod.rs b/tokio/src/runtime/mod.rs
index 08da39f4e6d..9419085379e 100644
--- a/tokio/src/runtime/mod.rs
+++ b/tokio/src/runtime/mod.rs
@@ -378,6 +378,7 @@ cfg_rt! {
         /// });
         /// # }
         /// ```
+        #[cfg_attr(tokio_track_caller, track_caller)]
         pub fn spawn<F>(&self, future: F) -> JoinHandle<F::Output>
         where
             F: Future + Send + 'static,
@@ -402,6 +403,7 @@ cfg_rt! {
         ///     println!("now running on a worker thread");
         /// });
         /// # }
+        #[cfg_attr(tokio_track_caller, track_caller)]
         pub fn spawn_blocking<F, R>(&self, func: F) -> JoinHandle<R>
         where
             F: FnOnce() -> R + Send + 'static,
diff --git a/tokio/src/task/blocking.rs b/tokio/src/task/blocking.rs
index fc6632be3b7..36bc4579bfe 100644
--- a/tokio/src/task/blocking.rs
+++ b/tokio/src/task/blocking.rs
@@ -104,6 +104,7 @@ cfg_rt_multi_thread! {
 /// # Ok(())
 /// # }
 /// ```
+#[cfg_attr(tokio_track_caller, track_caller)]
 pub fn spawn_blocking<F, R>(f: F) -> JoinHandle<R>
 where
     F: FnOnce() -> R + Send + 'static,
diff --git a/tokio/src/task/local.rs b/tokio/src/task/local.rs
index 5896126c7e5..566b2f2d7f8 100644
--- a/tokio/src/task/local.rs
+++ b/tokio/src/task/local.rs
@@ -190,6 +190,7 @@ cfg_rt! {
     ///     }).await;
     /// }
     /// ```
+    #[cfg_attr(tokio_track_caller, track_caller)]
     pub fn spawn_local<F>(future: F) -> JoinHandle<F::Output>
     where
         F: Future + 'static,
@@ -273,6 +274,7 @@ impl LocalSet {
     /// }
     /// ```
     /// [`spawn_local`]: fn@spawn_local
+    #[cfg_attr(tokio_track_caller, track_caller)]
     pub fn spawn_local<F>(&self, future: F) -> JoinHandle<F::Output>
     where
         F: Future + 'static,
diff --git a/tokio/src/task/spawn.rs b/tokio/src/task/spawn.rs
index 77acb579f73..a060852dc23 100644
--- a/tokio/src/task/spawn.rs
+++ b/tokio/src/task/spawn.rs
@@ -122,6 +122,7 @@ cfg_rt! {
     /// ```text
     /// error[E0391]: cycle detected when processing `main`
     /// ```
+    #[cfg_attr(tokio_track_caller, track_caller)]
     pub fn spawn<T>(task: T) -> JoinHandle<T::Output>
     where
         T: Future + Send + 'static,
diff --git a/tokio/src/util/trace.rs b/tokio/src/util/trace.rs
index 18956a36306..96a9db91d1f 100644
--- a/tokio/src/util/trace.rs
+++ b/tokio/src/util/trace.rs
@@ -1,47 +1,27 @@
 cfg_trace! {
     cfg_rt! {
-        use std::future::Future;
-        use std::pin::Pin;
-        use std::task::{Context, Poll};
-        use pin_project_lite::pin_project;
-
-        use tracing::Span;
-
-        pin_project! {
-            /// A future that has been instrumented with a `tracing` span.
-            #[derive(Debug, Clone)]
-            pub(crate) struct Instrumented<T> {
-                #[pin]
-                inner: T,
-                span: Span,
-            }
-        }
-
-        impl<T: Future> Future for Instrumented<T> {
-            type Output = T::Output;
-
-            fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-                let this = self.project();
-                let _enter = this.span.enter();
-                this.inner.poll(cx)
-            }
-        }
-
-        impl<T> Instrumented<T> {
-            pub(crate) fn new(inner: T, span: Span) -> Self {
-                Self { inner, span }
-            }
-        }
+        pub(crate) use tracing::instrument::Instrumented;
 
         #[inline]
+        #[cfg_attr(tokio_track_caller, track_caller)]
         pub(crate) fn task<F>(task: F, kind: &'static str) -> Instrumented<F> {
+            use tracing::instrument::Instrument;
+            #[cfg(tokio_track_caller)]
+            let location = std::panic::Location::caller();
+            #[cfg(tokio_track_caller)]
+            let span = tracing::trace_span!(
+                target: "tokio::task",
+                "task",
+                %kind,
+                spawn.location = %format_args!("{}:{}:{}", location.file(), location.line(), location.column()),
+            );
+            #[cfg(not(tokio_track_caller))]
             let span = tracing::trace_span!(
                 target: "tokio::task",
                 "task",
                 %kind,
-                future = %std::any::type_name::<F>(),
             );
-            Instrumented::new(task, span)
+            task.instrument(span)
         }
     }
 }