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Auto merge of #123265 - joboet:guardians_of_the_unix, r=ChrisDenton
Refactor stack overflow handling Currently, every platform must implement a `Guard` that protects a thread from stack overflow. However, UNIX is the only platform that actually does so. Windows has a different mechanism for detecting stack overflow, while the other platforms don't detect it at all. Also, the UNIX stack overflow handling is split between `sys::pal::unix::stack_overflow`, which implements the signal handler, and `sys::pal::unix::thread`, which detects/installs guard pages. This PR cleans this by getting rid of `Guard` and unifying UNIX stack overflow handling inside `stack_overflow` (commit 1). Therefore we can get rid of `sys_common::thread_info`, which stores `Guard` and the current `Thread` handle and move the `thread::current` TLS variable into `thread` (commit 2). The second commit is not strictly speaking necessary. To keep the implementation clean, I've included it here, but if it causes too much noise, I can split it out without any trouble.
2 parents 6bb6b81 + d7b55e4 commit c518e5a

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19 files changed

+327
-500
lines changed

19 files changed

+327
-500
lines changed

‎library/std/src/panicking.rs

+1-2
Original file line numberDiff line numberDiff line change
@@ -21,7 +21,6 @@ use crate::sync::atomic::{AtomicBool, Ordering};
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use crate::sync::{PoisonError, RwLock};
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use crate::sys::stdio::panic_output;
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use crate::sys_common::backtrace;
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use crate::sys_common::thread_info;
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use crate::thread;
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#[cfg(not(test))]
@@ -256,7 +255,7 @@ fn default_hook(info: &PanicInfo<'_>) {
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None => "Box<dyn Any>",
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},
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};
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let thread = thread_info::current_thread();
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let thread = thread::try_current();
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let name = thread.as_ref().and_then(|t| t.name()).unwrap_or("<unnamed>");
261260

262261
let write = |err: &mut dyn crate::io::Write| {

‎library/std/src/rt.rs

+3-8
Original file line numberDiff line numberDiff line change
@@ -24,8 +24,7 @@ pub use core::panicking::{panic_display, panic_fmt};
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use crate::sync::Once;
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use crate::sys;
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use crate::sys_common::thread_info;
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use crate::thread::Thread;
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use crate::thread::{self, Thread};
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// Prints to the "panic output", depending on the platform this may be:
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// - the standard error output
@@ -96,13 +95,9 @@ unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) {
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unsafe {
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sys::init(argc, argv, sigpipe);
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99-
let main_guard = sys::thread::guard::init();
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// Next, set up the current Thread with the guard information we just
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// created. Note that this isn't necessary in general for new threads,
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// but we just do this to name the main thread and to give it correct
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// info about the stack bounds.
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// Set up the current thread to give it the right name.
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let thread = Thread::new(Some(rtunwrap!(Ok, CString::new("main"))));
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thread_info::set(main_guard, thread);
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thread::set_current(thread);
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}
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}
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‎library/std/src/sys/pal/hermit/thread.rs

-10
Original file line numberDiff line numberDiff line change
@@ -104,13 +104,3 @@ impl Thread {
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pub fn available_parallelism() -> io::Result<NonZero<usize>> {
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unsafe { Ok(NonZero::new_unchecked(abi::get_processor_count())) }
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}
107-
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pub mod guard {
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pub type Guard = !;
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pub unsafe fn current() -> Option<Guard> {
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None
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}
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pub unsafe fn init() -> Option<Guard> {
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None
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}
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}

‎library/std/src/sys/pal/itron/thread.rs

-10
Original file line numberDiff line numberDiff line change
@@ -312,16 +312,6 @@ impl Drop for Thread {
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}
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}
314314

315-
pub mod guard {
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pub type Guard = !;
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pub unsafe fn current() -> Option<Guard> {
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None
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}
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pub unsafe fn init() -> Option<Guard> {
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None
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}
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}
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/// Terminate and delete the specified task.
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///
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/// This function will abort if `deleted_task` refers to the calling task.

‎library/std/src/sys/pal/sgx/thread.rs

-10
Original file line numberDiff line numberDiff line change
@@ -149,13 +149,3 @@ impl Thread {
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pub fn available_parallelism() -> io::Result<NonZero<usize>> {
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unsupported()
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}
152-
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pub mod guard {
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pub type Guard = !;
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pub unsafe fn current() -> Option<Guard> {
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None
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}
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pub unsafe fn init() -> Option<Guard> {
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None
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}
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}

‎library/std/src/sys/pal/teeos/thread.rs

-12
Original file line numberDiff line numberDiff line change
@@ -151,18 +151,6 @@ pub fn available_parallelism() -> io::Result<NonZero<usize>> {
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))
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}
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// stub
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pub mod guard {
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use crate::ops::Range;
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pub type Guard = Range<usize>;
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pub unsafe fn current() -> Option<Guard> {
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None
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}
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pub unsafe fn init() -> Option<Guard> {
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None
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}
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}
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fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {
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libc::PTHREAD_STACK_MIN.try_into().expect("Infallible")
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}

‎library/std/src/sys/pal/uefi/thread.rs

-10
Original file line numberDiff line numberDiff line change
@@ -52,13 +52,3 @@ pub fn available_parallelism() -> io::Result<NonZero<usize>> {
5252
// UEFI is single threaded
5353
Ok(NonZero::new(1).unwrap())
5454
}
55-
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pub mod guard {
57-
pub type Guard = !;
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pub unsafe fn current() -> Option<Guard> {
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None
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}
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pub unsafe fn init() -> Option<Guard> {
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None
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}
64-
}

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