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fixup(#7160 / tokio_epoll_uring_ext): double-panic caused by info! in thread-local's drop() (#7164)

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Manual testing of the changes in #7160 revealed that, if the
thread-local destructor ever runs (it apparently doesn't in our test
suite runs, otherwise #7160 would not have auto-merged), we can
encounter an `abort()` due to a double-panic in the tracing code.

This github comment here contains the stack trace:
https://github.com/neondatabase/neon/pull/7160#issuecomment-2003778176

This PR reverts #7160 and uses a atomic counter to identify the
thread-local in log messages, instead of the memory address of the
thread local, which may be re-used.
This commit is contained in:
Christian Schwarz
2024-03-18 16:12:01 +01:00
committed by Arpad Müller
parent fb2b1ce57b
commit 41fc96e20f
1 changed files with 8 additions and 21 deletions
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29
pageserver/src/virtual_file/io_engine/tokio_epoll_uring_ext.rs
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@@ -5,8 +5,8 @@
//! on older kernels, such as some (but not all) older kernels in the Linux 5.10 series.
//! See <https://github.com/neondatabase/neon/issues/6373#issuecomment-1905814391> for more details.
use std::sync::atomic::AtomicU32;
use std::sync::{Arc, Weak};
use std::sync::atomic::{AtomicU32, AtomicU64, Ordering};
use std::sync::Arc;
use tokio_util::sync::CancellationToken;
use tracing::{error, info, info_span, warn, Instrument};
@@ -24,38 +24,25 @@ struct ThreadLocalState(Arc<ThreadLocalStateInner>);
struct ThreadLocalStateInner {
cell: tokio::sync::OnceCell<SystemHandle>,
launch_attempts: AtomicU32,
weak_self: Weak<ThreadLocalStateInner>,
/// populated through fetch_add from [`THREAD_LOCAL_STATE_ID`]
thread_local_state_id: u64,
}
impl ThreadLocalState {
pub fn new() -> Self {
Self(Arc::new_cyclic(|weak| ThreadLocalStateInner {
Self(Arc::new(ThreadLocalStateInner {
cell: tokio::sync::OnceCell::default(),
launch_attempts: AtomicU32::new(0),
weak_self: Weak::clone(weak),
thread_local_state_id: THREAD_LOCAL_STATE_ID.fetch_add(1, Ordering::Relaxed),
}))
}
}
impl ThreadLocalStateInner {
pub fn make_id_string(&self) -> String {
format!("0x{:p}", self.weak_self.as_ptr())
format!("{}", self.0.thread_local_state_id)
}
}
impl Drop for ThreadLocalStateInner {
fn drop(&mut self) {
info!(parent: None, id=%self.make_id_string(), "tokio_epoll_uring_ext: thread-local state is being dropped and id might be re-used in the future");
}
}
impl std::ops::Deref for ThreadLocalState {
type Target = ThreadLocalStateInner;
fn deref(&self) -> &Self::Target {
&self.0
}
}
static THREAD_LOCAL_STATE_ID: AtomicU64 = AtomicU64::new(0);
thread_local! {
static THREAD_LOCAL: ThreadLocalState = ThreadLocalState::new();