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/group.rs | 293 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 293 insertions(+) create mode 100644 rust/syn/group.rs (limited to 'rust/syn/group.rs') diff --git a/rust/syn/group.rs b/rust/syn/group.rs new file mode 100644 index 000000000..57586c58f --- /dev/null +++ b/rust/syn/group.rs @@ -0,0 +1,293 @@ +// SPDX-License-Identifier: Apache-2.0 OR MIT + +use crate::error::Result; +use crate::parse::ParseBuffer; +use crate::token; +use proc_macro2::extra::DelimSpan; +use proc_macro2::Delimiter; + +// Not public API. +#[doc(hidden)] +pub struct Parens<'a> { + #[doc(hidden)] + pub token: token::Paren, + #[doc(hidden)] + pub content: ParseBuffer<'a>, +} + +// Not public API. +#[doc(hidden)] +pub struct Braces<'a> { + #[doc(hidden)] + pub token: token::Brace, + #[doc(hidden)] + pub content: ParseBuffer<'a>, +} + +// Not public API. +#[doc(hidden)] +pub struct Brackets<'a> { + #[doc(hidden)] + pub token: token::Bracket, + #[doc(hidden)] + pub content: ParseBuffer<'a>, +} + +// Not public API. +#[cfg(any(feature = "full", feature = "derive"))] +#[doc(hidden)] +pub struct Group<'a> { + #[doc(hidden)] + pub token: token::Group, + #[doc(hidden)] + pub content: ParseBuffer<'a>, +} + +// Not public API. +#[doc(hidden)] +pub fn parse_parens<'a>(input: &ParseBuffer<'a>) -> Result> { + parse_delimited(input, Delimiter::Parenthesis).map(|(span, content)| Parens { + token: token::Paren(span), + content, + }) +} + +// Not public API. +#[doc(hidden)] +pub fn parse_braces<'a>(input: &ParseBuffer<'a>) -> Result> { + parse_delimited(input, Delimiter::Brace).map(|(span, content)| Braces { + token: token::Brace(span), + content, + }) +} + +// Not public API. +#[doc(hidden)] +pub fn parse_brackets<'a>(input: &ParseBuffer<'a>) -> Result> { + parse_delimited(input, Delimiter::Bracket).map(|(span, content)| Brackets { + token: token::Bracket(span), + content, + }) +} + +#[cfg(any(feature = "full", feature = "derive"))] +pub(crate) fn parse_group<'a>(input: &ParseBuffer<'a>) -> Result> { + parse_delimited(input, Delimiter::None).map(|(span, content)| Group { + token: token::Group(span.join()), + content, + }) +} + +fn parse_delimited<'a>( + input: &ParseBuffer<'a>, + delimiter: Delimiter, +) -> Result<(DelimSpan, ParseBuffer<'a>)> { + input.step(|cursor| { + if let Some((content, span, rest)) = cursor.group(delimiter) { + let scope = span.close(); + let nested = crate::parse::advance_step_cursor(cursor, content); + let unexpected = crate::parse::get_unexpected(input); + let content = crate::parse::new_parse_buffer(scope, nested, unexpected); + Ok(((span, content), rest)) + } else { + let message = match delimiter { + Delimiter::Parenthesis => "expected parentheses", + Delimiter::Brace => "expected curly braces", + Delimiter::Bracket => "expected square brackets", + Delimiter::None => "expected invisible group", + }; + Err(cursor.error(message)) + } + }) +} + +/// Parse a set of parentheses and expose their content to subsequent parsers. +/// +/// # Example +/// +/// ``` +/// # use quote::quote; +/// # +/// use syn::{parenthesized, token, Ident, Result, Token, Type}; +/// use syn::parse::{Parse, ParseStream}; +/// use syn::punctuated::Punctuated; +/// +/// // Parse a simplified tuple struct syntax like: +/// // +/// // struct S(A, B); +/// struct TupleStruct { +/// struct_token: Token![struct], +/// ident: Ident, +/// paren_token: token::Paren, +/// fields: Punctuated, +/// semi_token: Token![;], +/// } +/// +/// impl Parse for TupleStruct { +/// fn parse(input: ParseStream) -> Result { +/// let content; +/// Ok(TupleStruct { +/// struct_token: input.parse()?, +/// ident: input.parse()?, +/// paren_token: parenthesized!(content in input), +/// fields: content.parse_terminated(Type::parse, Token![,])?, +/// semi_token: input.parse()?, +/// }) +/// } +/// } +/// # +/// # fn main() { +/// # let input = quote! { +/// # struct S(A, B); +/// # }; +/// # syn::parse2::(input).unwrap(); +/// # } +/// ``` +#[macro_export] +#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))] +macro_rules! parenthesized { + ($content:ident in $cursor:expr) => { + match $crate::__private::parse_parens(&$cursor) { + $crate::__private::Ok(parens) => { + $content = parens.content; + parens.token + } + $crate::__private::Err(error) => { + return $crate::__private::Err(error); + } + } + }; +} + +/// Parse a set of curly braces and expose their content to subsequent parsers. +/// +/// # Example +/// +/// ``` +/// # use quote::quote; +/// # +/// use syn::{braced, token, Ident, Result, Token, Type}; +/// use syn::parse::{Parse, ParseStream}; +/// use syn::punctuated::Punctuated; +/// +/// // Parse a simplified struct syntax like: +/// // +/// // struct S { +/// // a: A, +/// // b: B, +/// // } +/// struct Struct { +/// struct_token: Token![struct], +/// ident: Ident, +/// brace_token: token::Brace, +/// fields: Punctuated, +/// } +/// +/// struct Field { +/// name: Ident, +/// colon_token: Token![:], +/// ty: Type, +/// } +/// +/// impl Parse for Struct { +/// fn parse(input: ParseStream) -> Result { +/// let content; +/// Ok(Struct { +/// struct_token: input.parse()?, +/// ident: input.parse()?, +/// brace_token: braced!(content in input), +/// fields: content.parse_terminated(Field::parse, Token![,])?, +/// }) +/// } +/// } +/// +/// impl Parse for Field { +/// fn parse(input: ParseStream) -> Result { +/// Ok(Field { +/// name: input.parse()?, +/// colon_token: input.parse()?, +/// ty: input.parse()?, +/// }) +/// } +/// } +/// # +/// # fn main() { +/// # let input = quote! { +/// # struct S { +/// # a: A, +/// # b: B, +/// # } +/// # }; +/// # syn::parse2::(input).unwrap(); +/// # } +/// ``` +#[macro_export] +#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))] +macro_rules! braced { + ($content:ident in $cursor:expr) => { + match $crate::__private::parse_braces(&$cursor) { + $crate::__private::Ok(braces) => { + $content = braces.content; + braces.token + } + $crate::__private::Err(error) => { + return $crate::__private::Err(error); + } + } + }; +} + +/// Parse a set of square brackets and expose their content to subsequent +/// parsers. +/// +/// # Example +/// +/// ``` +/// # use quote::quote; +/// # +/// use proc_macro2::TokenStream; +/// use syn::{bracketed, token, Result, Token}; +/// use syn::parse::{Parse, ParseStream}; +/// +/// // Parse an outer attribute like: +/// // +/// // #[repr(C, packed)] +/// struct OuterAttribute { +/// pound_token: Token![#], +/// bracket_token: token::Bracket, +/// content: TokenStream, +/// } +/// +/// impl Parse for OuterAttribute { +/// fn parse(input: ParseStream) -> Result { +/// let content; +/// Ok(OuterAttribute { +/// pound_token: input.parse()?, +/// bracket_token: bracketed!(content in input), +/// content: content.parse()?, +/// }) +/// } +/// } +/// # +/// # fn main() { +/// # let input = quote! { +/// # #[repr(C, packed)] +/// # }; +/// # syn::parse2::(input).unwrap(); +/// # } +/// ``` +#[macro_export] +#[cfg_attr(docsrs, doc(cfg(feature = "parsing")))] +macro_rules! bracketed { + ($content:ident in $cursor:expr) => { + match $crate::__private::parse_brackets(&$cursor) { + $crate::__private::Ok(brackets) => { + $content = brackets.content; + brackets.token + } + $crate::__private::Err(error) => { + return $crate::__private::Err(error); + } + } + }; +} -- cgit v1.3.1