From 7280f3d28aa139cec0c75072a3e66294b7f99b59 Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Fri, 21 Oct 2022 17:44:35 -0700 Subject: [PATCH 1/2] Truncate thread names on Linux and Apple targets These targets have system limits on the thread names, 16 and 64 bytes respectively, and `pthread_setname_np` returns an error if the name is longer. However, we're not in a context that can propagate errors when we call this, and we used to implicitly truncate on Linux with `prctl`, so now we manually truncate these names ahead of time. --- library/std/src/sys/unix/thread.rs | 43 ++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) diff --git a/library/std/src/sys/unix/thread.rs b/library/std/src/sys/unix/thread.rs index 42ac6fcd8bf36..6a533854fad3d 100644 --- a/library/std/src/sys/unix/thread.rs +++ b/library/std/src/sys/unix/thread.rs @@ -132,8 +132,11 @@ impl Thread { #[cfg(target_os = "linux")] pub fn set_name(name: &CStr) { + const TASK_COMM_LEN: usize = 16; + unsafe { // Available since glibc 2.12, musl 1.1.16, and uClibc 1.0.20. + let name = truncate_cstr(name, TASK_COMM_LEN); libc::pthread_setname_np(libc::pthread_self(), name.as_ptr()); } } @@ -148,6 +151,7 @@ impl Thread { #[cfg(any(target_os = "macos", target_os = "ios", target_os = "watchos"))] pub fn set_name(name: &CStr) { unsafe { + let name = truncate_cstr(name, libc::MAXTHREADNAMESIZE); libc::pthread_setname_np(name.as_ptr()); } } @@ -276,6 +280,20 @@ impl Drop for Thread { } } +#[cfg(any(target_os = "linux", target_os = "macos", target_os = "ios", target_os = "watchos"))] +fn truncate_cstr(cstr: &CStr, max_with_nul: usize) -> crate::borrow::Cow<'_, CStr> { + use crate::{borrow::Cow, ffi::CString}; + + if cstr.to_bytes_with_nul().len() > max_with_nul { + let bytes = cstr.to_bytes()[..max_with_nul - 1].to_vec(); + // SAFETY: the non-nul bytes came straight from a CStr. + // (CString will add the terminating nul.) + Cow::Owned(unsafe { CString::from_vec_unchecked(bytes) }) + } else { + Cow::Borrowed(cstr) + } +} + pub fn available_parallelism() -> io::Result { cfg_if::cfg_if! { if #[cfg(any( @@ -902,3 +920,28 @@ fn min_stack_size(_: *const libc::pthread_attr_t) -> usize { fn min_stack_size(_: *const libc::pthread_attr_t) -> usize { 2048 // just a guess } + +#[test] +#[cfg(any(target_os = "linux", target_os = "macos", target_os = "ios", target_os = "watchos"))] +fn test_named_thread_truncation() { + use crate::thread::{self, Builder}; + + let long_name = crate::iter::once("test_named_thread_truncation") + .chain(crate::iter::repeat(" yada").take(100)) + .collect::(); + + let result = Builder::new().name(long_name.clone()).spawn(move || { + // Rust remembers the full thread name itself. + assert_eq!(thread::current().name(), Some(long_name.as_str())); + + // But the kernel is limited -- make sure we successfully set a truncation. + let mut buf = vec![0u8; long_name.len() + 1]; + unsafe { + libc::pthread_getname_np(libc::pthread_self(), buf.as_mut_ptr().cast(), buf.len()); + } + let cstr = CStr::from_bytes_until_nul(&buf).unwrap(); + assert!(cstr.to_bytes().len() > 0); + assert!(long_name.as_bytes().starts_with(cstr.to_bytes())); + }); + result.unwrap().join().unwrap(); +} From 12e45846ebbc32bd6a56f2de2658d3d9ad459032 Mon Sep 17 00:00:00 2001 From: Josh Stone Date: Fri, 21 Oct 2022 18:13:22 -0700 Subject: [PATCH 2/2] Move truncation next to other thread tests for tidy --- library/std/src/sys/unix/thread.rs | 25 ------------------------- library/std/src/thread/tests.rs | 25 +++++++++++++++++++++++++ 2 files changed, 25 insertions(+), 25 deletions(-) diff --git a/library/std/src/sys/unix/thread.rs b/library/std/src/sys/unix/thread.rs index 6a533854fad3d..69cd2b500a1f0 100644 --- a/library/std/src/sys/unix/thread.rs +++ b/library/std/src/sys/unix/thread.rs @@ -920,28 +920,3 @@ fn min_stack_size(_: *const libc::pthread_attr_t) -> usize { fn min_stack_size(_: *const libc::pthread_attr_t) -> usize { 2048 // just a guess } - -#[test] -#[cfg(any(target_os = "linux", target_os = "macos", target_os = "ios", target_os = "watchos"))] -fn test_named_thread_truncation() { - use crate::thread::{self, Builder}; - - let long_name = crate::iter::once("test_named_thread_truncation") - .chain(crate::iter::repeat(" yada").take(100)) - .collect::(); - - let result = Builder::new().name(long_name.clone()).spawn(move || { - // Rust remembers the full thread name itself. - assert_eq!(thread::current().name(), Some(long_name.as_str())); - - // But the kernel is limited -- make sure we successfully set a truncation. - let mut buf = vec![0u8; long_name.len() + 1]; - unsafe { - libc::pthread_getname_np(libc::pthread_self(), buf.as_mut_ptr().cast(), buf.len()); - } - let cstr = CStr::from_bytes_until_nul(&buf).unwrap(); - assert!(cstr.to_bytes().len() > 0); - assert!(long_name.as_bytes().starts_with(cstr.to_bytes())); - }); - result.unwrap().join().unwrap(); -} diff --git a/library/std/src/thread/tests.rs b/library/std/src/thread/tests.rs index dfb8765ab4eed..71eb41cd564db 100644 --- a/library/std/src/thread/tests.rs +++ b/library/std/src/thread/tests.rs @@ -37,6 +37,31 @@ fn test_named_thread() { .unwrap(); } +#[cfg(any(target_os = "linux", target_os = "macos", target_os = "ios", target_os = "watchos"))] +#[test] +fn test_named_thread_truncation() { + use crate::ffi::CStr; + + let long_name = crate::iter::once("test_named_thread_truncation") + .chain(crate::iter::repeat(" yada").take(100)) + .collect::(); + + let result = Builder::new().name(long_name.clone()).spawn(move || { + // Rust remembers the full thread name itself. + assert_eq!(thread::current().name(), Some(long_name.as_str())); + + // But the system is limited -- make sure we successfully set a truncation. + let mut buf = vec![0u8; long_name.len() + 1]; + unsafe { + libc::pthread_getname_np(libc::pthread_self(), buf.as_mut_ptr().cast(), buf.len()); + } + let cstr = CStr::from_bytes_until_nul(&buf).unwrap(); + assert!(cstr.to_bytes().len() > 0); + assert!(long_name.as_bytes().starts_with(cstr.to_bytes())); + }); + result.unwrap().join().unwrap(); +} + #[test] #[should_panic] fn test_invalid_named_thread() {