From 9cc63f8bcd560c760d0b12e15bba8f81c86237cf Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <paulmck@kernel.org>
Date: Fri, 14 Aug 2026 15:43:51 -0700
Subject: Merge branches 'expcb.2026.07.24a', 'misc.2026.07.30a',
 'rcu-tasks.2026.07.30a', 'srcu.2026.08.11a' and 'torture.2026.08.14a' into
 HEAD

Changes:

Make expedited grace periods expedite normal RCU callbacks

Miscellaneous fixes:
 * Improve diagnostic output with character task states.
 * Mark accesses to inform KCSAN of concurrency design.
 * Move from kmalloc() to kmalloc_obj().
 * Documentation updates.
 * Improve handling of RCU deferred quiescent states.
 * Clean up unused function arguments and structure fields.
 * Reduce show_rcu_gp_kthreads() stack space.

Tasks RCU updates:
 * Clean up after SRCU re-implementation of Tasks Trace RCU.
 * Mark accesses to inform KCSAN of concurrency design.
 * Add ->lazy_timer status to diagnostic output.
 * Remove an unnecessary memory barrier.
 * Fix a data race, courtesy of KCSAN.
 * Documentation updates.
 * Convert cond_resched_tasks_rcu_qs() from macro to static inline
   function.

SRCU updates:
 * Add Rust helpers for SRCU.
 * Avoid losing queued work at cleanup_srcu_struct() time.

Torture-test updates:
 * Preparation work for immediate RCU priority deboosting.
 * Test RCU readers from real interrupt handlers (as opposed to softirq).
 * Simplify code through use of cpumask_next_wrap().
 * Improve diagnostic output with character task states.
 * Add rcutorture.nwriters parameter to allow lightweight stall testing,
   and rcutorture.stall_only to make doing so easier.
 * Test an RCU Tasks Trace grace period implying an RCU grace period.
 * Make RCU Tasks Trace torturing track reader batches.
 * Fix a data race, courtesy of KCSAN.
 * Plug a shuffle_tmp_mask memory leak on kthread spawn failure.
---
 rust/syn/ident.rs | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 rust/syn/ident.rs

(limited to 'rust/syn/ident.rs')

diff --git a/rust/syn/ident.rs b/rust/syn/ident.rs
new file mode 100644
index 000000000..03ccebf9c
--- /dev/null
+++ b/rust/syn/ident.rs
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+#[cfg(feature = "parsing")]
+use crate::lookahead;
+
+pub use proc_macro2::Ident;
+
+#[cfg(feature = "parsing")]
+pub_if_not_doc! {
+    #[doc(hidden)]
+    #[allow(non_snake_case)]
+    pub fn Ident(marker: lookahead::TokenMarker) -> Ident {
+        match marker {}
+    }
+}
+
+macro_rules! ident_from_token {
+    ($token:ident) => {
+        impl From<Token![$token]> for Ident {
+            fn from(token: Token![$token]) -> Ident {
+                Ident::new(stringify!($token), token.span)
+            }
+        }
+    };
+}
+
+ident_from_token!(self);
+ident_from_token!(Self);
+ident_from_token!(super);
+ident_from_token!(crate);
+ident_from_token!(extern);
+
+impl From<Token![_]> for Ident {
+    fn from(token: Token![_]) -> Ident {
+        Ident::new("_", token.span)
+    }
+}
+
+pub(crate) fn xid_ok(symbol: &str) -> bool {
+    let mut chars = symbol.chars();
+    let first = chars.next().unwrap();
+    if !(first == '_' || first.is_ascii_alphabetic()) {
+        return false;
+    }
+    for ch in chars {
+        if !(ch == '_' || ch.is_ascii_alphanumeric()) {
+            return false;
+        }
+    }
+    true
+}
+
+#[cfg(feature = "parsing")]
+mod parsing {
+    use crate::buffer::Cursor;
+    use crate::error::Result;
+    use crate::parse::{Parse, ParseStream};
+    use crate::token::Token;
+    use proc_macro2::Ident;
+
+    fn accept_as_ident(ident: &Ident) -> bool {
+        match ident.to_string().as_str() {
+            "_" |
+            // Based on https://doc.rust-lang.org/1.65.0/reference/keywords.html
+            "abstract" | "as" | "async" | "await" | "become" | "box" | "break" |
+            "const" | "continue" | "crate" | "do" | "dyn" | "else" | "enum" |
+            "extern" | "false" | "final" | "fn" | "for" | "if" | "impl" | "in" |
+            "let" | "loop" | "macro" | "match" | "mod" | "move" | "mut" |
+            "override" | "priv" | "pub" | "ref" | "return" | "Self" | "self" |
+            "static" | "struct" | "super" | "trait" | "true" | "try" | "type" |
+            "typeof" | "unsafe" | "unsized" | "use" | "virtual" | "where" |
+            "while" | "yield" => false,
+            _ => true,
+        }
+    }
+
+    #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
+    impl Parse for Ident {
+        fn parse(input: ParseStream) -> Result<Self> {
+            input.step(|cursor| {
+                if let Some((ident, rest)) = cursor.ident() {
+                    if accept_as_ident(&ident) {
+                        Ok((ident, rest))
+                    } else {
+                        Err(cursor.error(format_args!(
+                            "expected identifier, found keyword `{}`",
+                            ident,
+                        )))
+                    }
+                } else {
+                    Err(cursor.error("expected identifier"))
+                }
+            })
+        }
+    }
+
+    impl Token for Ident {
+        fn peek(cursor: Cursor) -> bool {
+            if let Some((ident, _rest)) = cursor.ident() {
+                accept_as_ident(&ident)
+            } else {
+                false
+            }
+        }
+
+        fn display() -> &'static str {
+            "identifier"
+        }
+    }
+}
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