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 HEADgrafted

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.

1 files changed, 75 insertions, 0 deletions

diff --git a/include/asm-generic/atomic64.h b/include/asm-generic/atomic64.h
new file mode 100644
index 000000000..f22ccfc0d
--- /dev/null
+++ b/include/asm-generic/atomic64.h
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Generic implementation of 64-bit atomics using spinlocks,
+ * useful on processors that don't have 64-bit atomic instructions.
+ *
+ * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
+ */
+#ifndef _ASM_GENERIC_ATOMIC64_H
+#define _ASM_GENERIC_ATOMIC64_H
+#include <linux/types.h>
+
+typedef struct {
+	s64 __aligned(sizeof(s64)) counter;
+} atomic64_t;
+
+#define ATOMIC64_INIT(i)	{ (i) }
+
+extern s64 generic_atomic64_read(const atomic64_t *v);
+extern void generic_atomic64_set(atomic64_t *v, s64 i);
+
+#define ATOMIC64_OP(op)							\
+extern void generic_atomic64_##op(s64 a, atomic64_t *v);
+
+#define ATOMIC64_OP_RETURN(op)						\
+extern s64 generic_atomic64_##op##_return(s64 a, atomic64_t *v);
+
+#define ATOMIC64_FETCH_OP(op)						\
+extern s64 generic_atomic64_fetch_##op(s64 a, atomic64_t *v);
+
+#define ATOMIC64_OPS(op)	ATOMIC64_OP(op) ATOMIC64_OP_RETURN(op) ATOMIC64_FETCH_OP(op)
+
+ATOMIC64_OPS(add)
+ATOMIC64_OPS(sub)
+
+#undef ATOMIC64_OPS
+#define ATOMIC64_OPS(op)	ATOMIC64_OP(op) ATOMIC64_FETCH_OP(op)
+
+ATOMIC64_OPS(and)
+ATOMIC64_OPS(or)
+ATOMIC64_OPS(xor)
+
+#undef ATOMIC64_OPS
+#undef ATOMIC64_FETCH_OP
+#undef ATOMIC64_OP_RETURN
+#undef ATOMIC64_OP
+
+extern s64 generic_atomic64_dec_if_positive(atomic64_t *v);
+extern s64 generic_atomic64_cmpxchg(atomic64_t *v, s64 o, s64 n);
+extern s64 generic_atomic64_xchg(atomic64_t *v, s64 new);
+extern s64 generic_atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u);
+
+#define arch_atomic64_read		generic_atomic64_read
+#define arch_atomic64_set		generic_atomic64_set
+#define arch_atomic64_set_release	generic_atomic64_set
+
+#define arch_atomic64_add		generic_atomic64_add
+#define arch_atomic64_add_return	generic_atomic64_add_return
+#define arch_atomic64_fetch_add		generic_atomic64_fetch_add
+#define arch_atomic64_sub		generic_atomic64_sub
+#define arch_atomic64_sub_return	generic_atomic64_sub_return
+#define arch_atomic64_fetch_sub		generic_atomic64_fetch_sub
+
+#define arch_atomic64_and		generic_atomic64_and
+#define arch_atomic64_fetch_and		generic_atomic64_fetch_and
+#define arch_atomic64_or		generic_atomic64_or
+#define arch_atomic64_fetch_or		generic_atomic64_fetch_or
+#define arch_atomic64_xor		generic_atomic64_xor
+#define arch_atomic64_fetch_xor		generic_atomic64_fetch_xor
+
+#define arch_atomic64_dec_if_positive	generic_atomic64_dec_if_positive
+#define arch_atomic64_cmpxchg		generic_atomic64_cmpxchg
+#define arch_atomic64_xchg		generic_atomic64_xchg
+#define arch_atomic64_fetch_add_unless	generic_atomic64_fetch_add_unless
+
+#endif  /*  _ASM_GENERIC_ATOMIC64_H  */