Rollup merge of #121666 - ChrisDenton:thread-name, r=cuviper

Use the OS thread name by default if `THREAD_INFO` has not been initialized

Currently if `THREAD_INFO` hasn't been initialized then the name will be set to `None`.  This PR changes it to use the OS thread name by default. This mostly affects foreign threads at the moment but we could expand this to make more use of the OS thread name in the future.

Note: I've only implemented `Thread::get_name` for windows, linux and macos (and macos adjacent) targets. The rest just return `None`.

15 files changed, 137 insertions, 11 deletions

diff --git a/library/std/src/sys/pal/hermit/thread.rs b/library/std/src/sys/pal/hermit/thread.rs
index fee80c02d4a..cf45b9c2396 100644
--- a/library/std/src/sys/pal/hermit/thread.rs
+++ b/library/std/src/sys/pal/hermit/thread.rs
@@ -2,7 +2,7 @@
 
 use super::abi;
 use super::thread_local_dtor::run_dtors;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -71,6 +71,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     #[inline]
     pub fn sleep(dur: Duration) {
         unsafe {
diff --git a/library/std/src/sys/pal/itron/thread.rs b/library/std/src/sys/pal/itron/thread.rs
index 9c1387bf408..814a102dd09 100644
--- a/library/std/src/sys/pal/itron/thread.rs
+++ b/library/std/src/sys/pal/itron/thread.rs
@@ -8,7 +8,7 @@ use super::{
 };
 use crate::{
     cell::UnsafeCell,
-    ffi::CStr,
+    ffi::{CStr, CString},
     hint, io,
     mem::ManuallyDrop,
     num::NonZero,
@@ -204,6 +204,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         for timeout in dur2reltims(dur) {
             expect_success(unsafe { abi::dly_tsk(timeout) }, &"dly_tsk");
diff --git a/library/std/src/sys/pal/sgx/thread.rs b/library/std/src/sys/pal/sgx/thread.rs
index c797fde7fbd..77f68bf7334 100644
--- a/library/std/src/sys/pal/sgx/thread.rs
+++ b/library/std/src/sys/pal/sgx/thread.rs
@@ -1,6 +1,6 @@
 #![cfg_attr(test, allow(dead_code))] // why is this necessary?
 use super::unsupported;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::num::NonZero;
 use crate::time::Duration;
@@ -133,6 +133,10 @@ impl Thread {
         // which succeeds as-is with the SGX target.
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         usercalls::wait_timeout(0, dur, || true);
     }
diff --git a/library/std/src/sys/pal/teeos/thread.rs b/library/std/src/sys/pal/teeos/thread.rs
index 77f9040ead5..b76bcf9bbb0 100644
--- a/library/std/src/sys/pal/teeos/thread.rs
+++ b/library/std/src/sys/pal/teeos/thread.rs
@@ -1,7 +1,7 @@
 use core::convert::TryInto;
 
 use crate::cmp;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -101,6 +101,10 @@ impl Thread {
         // contact the teeos rustzone team.
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     /// only main thread could wait for sometime in teeos
     pub fn sleep(dur: Duration) {
         let sleep_millis = dur.as_millis();
diff --git a/library/std/src/sys/pal/uefi/thread.rs b/library/std/src/sys/pal/uefi/thread.rs
index 3d8fa27251f..b3a4f9c53e3 100644
--- a/library/std/src/sys/pal/uefi/thread.rs
+++ b/library/std/src/sys/pal/uefi/thread.rs
@@ -1,5 +1,5 @@
 use super::unsupported;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::num::NonZero;
 use crate::ptr::NonNull;
@@ -23,6 +23,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         let boot_services: NonNull<r_efi::efi::BootServices> =
             crate::os::uefi::env::boot_services().expect("can't sleep").cast();
diff --git a/library/std/src/sys/pal/unix/thread.rs b/library/std/src/sys/pal/unix/thread.rs
index 864de31c6eb..2af6382f3da 100644
--- a/library/std/src/sys/pal/unix/thread.rs
+++ b/library/std/src/sys/pal/unix/thread.rs
@@ -1,5 +1,5 @@
 use crate::cmp;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -225,6 +225,44 @@ impl Thread {
         // Newlib, Emscripten, and VxWorks have no way to set a thread name.
     }
 
+    #[cfg(target_os = "linux")]
+    pub fn get_name() -> Option<CString> {
+        const TASK_COMM_LEN: usize = 16;
+        let mut name = vec![0u8; TASK_COMM_LEN];
+        let res = unsafe {
+            libc::pthread_getname_np(libc::pthread_self(), name.as_mut_ptr().cast(), name.len())
+        };
+        if res != 0 {
+            return None;
+        }
+        name.truncate(name.iter().position(|&c| c == 0)?);
+        CString::new(name).ok()
+    }
+
+    #[cfg(any(target_os = "macos", target_os = "ios", target_os = "tvos", target_os = "watchos"))]
+    pub fn get_name() -> Option<CString> {
+        let mut name = vec![0u8; libc::MAXTHREADNAMESIZE];
+        let res = unsafe {
+            libc::pthread_getname_np(libc::pthread_self(), name.as_mut_ptr().cast(), name.len())
+        };
+        if res != 0 {
+            return None;
+        }
+        name.truncate(name.iter().position(|&c| c == 0)?);
+        CString::new(name).ok()
+    }
+
+    #[cfg(not(any(
+        target_os = "linux",
+        target_os = "macos",
+        target_os = "ios",
+        target_os = "tvos",
+        target_os = "watchos"
+    )))]
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     #[cfg(not(target_os = "espidf"))]
     pub fn sleep(dur: Duration) {
         let mut secs = dur.as_secs();
diff --git a/library/std/src/sys/pal/unsupported/thread.rs b/library/std/src/sys/pal/unsupported/thread.rs
index cd1ae7f7d11..b3a91ee1d4c 100644
--- a/library/std/src/sys/pal/unsupported/thread.rs
+++ b/library/std/src/sys/pal/unsupported/thread.rs
@@ -1,5 +1,5 @@
 use super::unsupported;
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::num::NonZero;
 use crate::time::Duration;
@@ -22,6 +22,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(_dur: Duration) {
         panic!("can't sleep");
     }
diff --git a/library/std/src/sys/pal/wasi/thread.rs b/library/std/src/sys/pal/wasi/thread.rs
index 77d8b4378e7..4b116052f8f 100644
--- a/library/std/src/sys/pal/wasi/thread.rs
+++ b/library/std/src/sys/pal/wasi/thread.rs
@@ -1,4 +1,4 @@
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::mem;
 use crate::num::NonZero;
@@ -134,6 +134,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         let nanos = dur.as_nanos();
         assert!(nanos <= u64::MAX as u128);
diff --git a/library/std/src/sys/pal/windows/c.rs b/library/std/src/sys/pal/windows/c.rs
index b007796722b..afa92409404 100644
--- a/library/std/src/sys/pal/windows/c.rs
+++ b/library/std/src/sys/pal/windows/c.rs
@@ -344,6 +344,12 @@ compat_fn_with_fallback! {
         SetLastError(ERROR_CALL_NOT_IMPLEMENTED as DWORD); E_NOTIMPL
     }
 
+    // >= Win10 1607
+    // https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-getthreaddescription
+    pub fn GetThreadDescription(hthread: HANDLE, lpthreaddescription: *mut PWSTR) -> HRESULT {
+        SetLastError(ERROR_CALL_NOT_IMPLEMENTED as DWORD); E_NOTIMPL
+    }
+
     // >= Win8 / Server 2012
     // https://docs.microsoft.com/en-us/windows/win32/api/sysinfoapi/nf-sysinfoapi-getsystemtimepreciseasfiletime
     pub fn GetSystemTimePreciseAsFileTime(lpsystemtimeasfiletime: *mut FILETIME) -> () {
diff --git a/library/std/src/sys/pal/windows/c/bindings.txt b/library/std/src/sys/pal/windows/c/bindings.txt
index ab2a8caf5df..d0081411530 100644
--- a/library/std/src/sys/pal/windows/c/bindings.txt
+++ b/library/std/src/sys/pal/windows/c/bindings.txt
@@ -1923,6 +1923,7 @@ Windows.Win32.Foundation.HANDLE_FLAG_INHERIT
 Windows.Win32.Foundation.HANDLE_FLAG_PROTECT_FROM_CLOSE
 Windows.Win32.Foundation.HANDLE_FLAGS
 Windows.Win32.Foundation.HMODULE
+Windows.Win32.Foundation.LocalFree
 Windows.Win32.Foundation.MAX_PATH
 Windows.Win32.Foundation.NO_ERROR
 Windows.Win32.Foundation.NTSTATUS
diff --git a/library/std/src/sys/pal/windows/c/windows_sys.rs b/library/std/src/sys/pal/windows/c/windows_sys.rs
index 8eb779373f7..96773d91e99 100644
--- a/library/std/src/sys/pal/windows/c/windows_sys.rs
+++ b/library/std/src/sys/pal/windows/c/windows_sys.rs
@@ -380,6 +380,10 @@ extern "system" {
 }
 #[link(name = "kernel32")]
 extern "system" {
+    pub fn LocalFree(hmem: HLOCAL) -> HLOCAL;
+}
+#[link(name = "kernel32")]
+extern "system" {
     pub fn MoveFileExW(
         lpexistingfilename: PCWSTR,
         lpnewfilename: PCWSTR,
@@ -3441,6 +3445,7 @@ pub type HANDLE_FLAGS = u32;
 pub const HANDLE_FLAG_INHERIT: HANDLE_FLAGS = 1u32;
 pub const HANDLE_FLAG_PROTECT_FROM_CLOSE: HANDLE_FLAGS = 2u32;
 pub const HIGH_PRIORITY_CLASS: PROCESS_CREATION_FLAGS = 128u32;
+pub type HLOCAL = *mut ::core::ffi::c_void;
 pub type HMODULE = *mut ::core::ffi::c_void;
 pub type HRESULT = i32;
 pub const IDLE_PRIORITY_CLASS: PROCESS_CREATION_FLAGS = 64u32;
diff --git a/library/std/src/sys/pal/windows/thread.rs b/library/std/src/sys/pal/windows/thread.rs
index 0f709e2ec7b..a8f1e9b726b 100644
--- a/library/std/src/sys/pal/windows/thread.rs
+++ b/library/std/src/sys/pal/windows/thread.rs
@@ -9,7 +9,7 @@ use crate::sys::handle::Handle;
 use crate::sys::stack_overflow;
 use crate::sys_common::FromInner;
 use crate::time::Duration;
-
+use alloc::ffi::CString;
 use core::ffi::c_void;
 
 use super::time::WaitableTimer;
@@ -71,6 +71,29 @@ impl Thread {
         };
     }
 
+    pub fn get_name() -> Option<CString> {
+        unsafe {
+            let mut ptr = core::ptr::null_mut();
+            let result = c::GetThreadDescription(c::GetCurrentThread(), &mut ptr);
+            if result < 0 {
+                return None;
+            }
+            let name = String::from_utf16_lossy({
+                let mut len = 0;
+                while *ptr.add(len) != 0 {
+                    len += 1;
+                }
+                core::slice::from_raw_parts(ptr, len)
+            })
+            .into_bytes();
+            // Attempt to free the memory.
+            // This should never fail but if it does then there's not much we can do about it.
+            let result = c::LocalFree(ptr.cast::<c_void>());
+            debug_assert!(result.is_null());
+            if name.is_empty() { None } else { Some(CString::from_vec_unchecked(name)) }
+        }
+    }
+
     pub fn join(self) {
         let rc = unsafe { c::WaitForSingleObject(self.handle.as_raw_handle(), c::INFINITE) };
         if rc == c::WAIT_FAILED {
diff --git a/library/std/src/sys/pal/xous/thread.rs b/library/std/src/sys/pal/xous/thread.rs
index 21f5954d6e2..f95ceb7343b 100644
--- a/library/std/src/sys/pal/xous/thread.rs
+++ b/library/std/src/sys/pal/xous/thread.rs
@@ -1,4 +1,4 @@
-use crate::ffi::CStr;
+use crate::ffi::{CStr, CString};
 use crate::io;
 use crate::num::NonZero;
 use crate::os::xous::ffi::{
@@ -113,6 +113,10 @@ impl Thread {
         // nope
     }
 
+    pub fn get_name() -> Option<CString> {
+        None
+    }
+
     pub fn sleep(dur: Duration) {
         // Because the sleep server works on units of `usized milliseconds`, split
         // the messages up into these chunks. This means we may run into issues
diff --git a/library/std/src/sys_common/thread_info.rs b/library/std/src/sys_common/thread_info.rs
index 8d51732e035..ec1428ea40e 100644
--- a/library/std/src/sys_common/thread_info.rs
+++ b/library/std/src/sys_common/thread_info.rs
@@ -1,6 +1,7 @@
 #![allow(dead_code)] // stack_guard isn't used right now on all platforms
 
 use crate::cell::OnceCell;
+use crate::sys;
 use crate::sys::thread::guard::Guard;
 use crate::thread::Thread;
 
@@ -23,7 +24,8 @@ impl ThreadInfo {
     {
         THREAD_INFO
             .try_with(move |thread_info| {
-                let thread = thread_info.thread.get_or_init(|| Thread::new(None));
+                let thread =
+                    thread_info.thread.get_or_init(|| Thread::new(sys::thread::Thread::get_name()));
                 f(thread, &thread_info.stack_guard)
             })
             .ok()
diff --git a/library/std/src/thread/tests.rs b/library/std/src/thread/tests.rs
index 5d6b9e94ee9..efd06c8df6e 100644
--- a/library/std/src/thread/tests.rs
+++ b/library/std/src/thread/tests.rs
@@ -69,6 +69,25 @@ fn test_named_thread_truncation() {
     result.unwrap().join().unwrap();
 }
 
+#[cfg(any(
+    target_os = "windows",
+    target_os = "linux",
+    target_os = "macos",
+    target_os = "ios",
+    target_os = "tvos",
+    target_os = "watchos"
+))]
+#[test]
+fn test_get_os_named_thread() {
+    use crate::sys::thread::Thread;
+    let handler = thread::spawn(|| {
+        let name = c"test me please";
+        Thread::set_name(name);
+        assert_eq!(name, Thread::get_name().unwrap().as_c_str());
+    });
+    handler.join().unwrap();
+}
+
 #[test]
 #[should_panic]
 fn test_invalid_named_thread() {