From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug alb_break_llc() decides whether to break LLC preference during active load balance. It does so by testing that every runnable fair task on the source rq prefers its LLC: env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable But the two counters cover different sets. nr_pref_llc_running is updated in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued, so it follows queued tasks. h_nr_runnable is updated in set_delayed()/ clear_delayed() and drops delay-dequeued tasks. So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks, alb_break_llc() returns false, and active balance is free to pull a task off its preferred LLC. Active balance only moves runnable tasks, and this is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB skips the per-task test in can_migrate_task(). The runnable set is the one we want. Fix it on the counter side. A task should be counted in nr_pref_llc_running exactly while it is both queued on its preferred LLC (pref_llc_queued) and runnable (!sched_delayed). Define that membership once in task_pref_llc_runnable(), and adjust the counter only through pref_llc_running_inc()/pref_llc_running_dec() from the four sites that change either input: account_llc_enqueue(), account_llc_dequeue(), set_delayed() and clear_delayed(). Gating every update on the same predicate keeps the delay, wake and dequeue paths from double-counting or underflowing; see the comments at those sites for the ordering. nr_llc_running and sd->llc_counts are not touched and stay on queued semantics. Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC") Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/ Reported-by: Zhan Xusheng Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- rust/syn/export.rs | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) create mode 100644 rust/syn/export.rs (limited to 'rust/syn/export.rs') diff --git a/rust/syn/export.rs b/rust/syn/export.rs new file mode 100644 index 000000000..05dad324b --- /dev/null +++ b/rust/syn/export.rs @@ -0,0 +1,75 @@ +// SPDX-License-Identifier: Apache-2.0 OR MIT + +#[doc(hidden)] +pub use std::clone::Clone; +#[doc(hidden)] +pub use std::cmp::{Eq, PartialEq}; +#[doc(hidden)] +pub use std::concat; +#[doc(hidden)] +pub use std::default::Default; +#[doc(hidden)] +pub use std::fmt::Debug; +#[doc(hidden)] +pub use std::hash::{Hash, Hasher}; +#[doc(hidden)] +pub use std::marker::Copy; +#[doc(hidden)] +pub use std::option::Option::{None, Some}; +#[doc(hidden)] +pub use std::result::Result::{Err, Ok}; +#[doc(hidden)] +pub use std::stringify; + +#[doc(hidden)] +pub type Formatter<'a> = std::fmt::Formatter<'a>; +#[doc(hidden)] +pub type FmtResult = std::fmt::Result; + +#[doc(hidden)] +pub type bool = std::primitive::bool; +#[doc(hidden)] +pub type str = std::primitive::str; + +#[cfg(feature = "printing")] +#[doc(hidden)] +pub use quote; + +#[doc(hidden)] +pub type Span = proc_macro2::Span; +#[doc(hidden)] +pub type TokenStream2 = proc_macro2::TokenStream; + +#[cfg(feature = "parsing")] +#[doc(hidden)] +pub use crate::group::{parse_braces, parse_brackets, parse_parens}; + +#[doc(hidden)] +pub use crate::span::IntoSpans; + +#[cfg(all(feature = "parsing", feature = "printing"))] +#[doc(hidden)] +pub use crate::parse_quote::parse as parse_quote; + +#[cfg(feature = "parsing")] +#[doc(hidden)] +pub use crate::token::parsing::{peek_punct, punct as parse_punct}; + +#[cfg(feature = "printing")] +#[doc(hidden)] +pub use crate::token::printing::punct as print_punct; + +#[cfg(feature = "parsing")] +#[doc(hidden)] +pub use crate::token::private::CustomToken; + +#[cfg(feature = "proc-macro")] +#[doc(hidden)] +pub type TokenStream = proc_macro::TokenStream; + +#[cfg(feature = "printing")] +#[doc(hidden)] +pub use quote::{ToTokens, TokenStreamExt}; + +#[doc(hidden)] +pub struct private(pub(crate) ()); -- cgit v1.3.1