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, 52 insertions, 0 deletions

diff --git a/scripts/Makefile.debug b/scripts/Makefile.debug
new file mode 100644
index 000000000..107db997c
--- /dev/null
+++ b/scripts/Makefile.debug
@@ -0,0 +1,52 @@
+DEBUG_CFLAGS	:=
+DEBUG_RUSTFLAGS	:=
+
+debug-flags-y	:= -g
+
+ifdef CONFIG_DEBUG_INFO_SPLIT
+DEBUG_CFLAGS	+= -gsplit-dwarf
+endif
+
+debug-flags-$(CONFIG_DEBUG_INFO_DWARF4)	+= -gdwarf-4
+debug-flags-$(CONFIG_DEBUG_INFO_DWARF5)	+= -gdwarf-5
+ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_AS_IS_GNU),yy)
+# Clang does not pass -g or -gdwarf-* option down to GAS.
+# Add -Wa, prefix to explicitly specify the flags.
+KBUILD_AFLAGS	+= $(addprefix -Wa$(comma), $(debug-flags-y))
+endif
+DEBUG_CFLAGS	+= $(debug-flags-y)
+KBUILD_AFLAGS	+= $(debug-flags-y)
+
+ifdef CONFIG_DEBUG_INFO_DWARF4
+DEBUG_RUSTFLAGS	+= -Zdwarf-version=4
+else ifdef CONFIG_DEBUG_INFO_DWARF5
+DEBUG_RUSTFLAGS	+= -Zdwarf-version=5
+endif
+
+ifdef CONFIG_DEBUG_INFO_REDUCED
+DEBUG_CFLAGS	+= -fno-var-tracking
+DEBUG_RUSTFLAGS	+= -Cdebuginfo=1
+ifdef CONFIG_CC_IS_GCC
+DEBUG_CFLAGS	+= -femit-struct-debug-baseonly
+endif
+else
+DEBUG_RUSTFLAGS	+= -Cdebuginfo=2
+endif
+
+ifdef CONFIG_DEBUG_INFO_COMPRESSED_ZLIB
+DEBUG_CFLAGS	+= -gz=zlib
+DEBUG_RUSTFLAGS	+= -Zdebuginfo-compression=zlib
+KBUILD_AFLAGS	+= -gz=zlib
+KBUILD_LDFLAGS	+= --compress-debug-sections=zlib
+else ifdef CONFIG_DEBUG_INFO_COMPRESSED_ZSTD
+DEBUG_CFLAGS	+= -gz=zstd
+DEBUG_RUSTFLAGS	+= -Zdebuginfo-compression=zstd
+KBUILD_AFLAGS	+= -gz=zstd
+KBUILD_LDFLAGS	+= --compress-debug-sections=zstd
+endif
+
+KBUILD_CFLAGS	+= $(DEBUG_CFLAGS)
+export DEBUG_CFLAGS
+
+KBUILD_RUSTFLAGS += $(DEBUG_RUSTFLAGS)
+export DEBUG_RUSTFLAGS