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, 108 insertions, 0 deletions

diff --git a/arch/arc/Makefile b/arch/arc/Makefile
new file mode 100644
index 000000000..868805ffc
--- /dev/null
+++ b/arch/arc/Makefile
@@ -0,0 +1,108 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+#
+
+KBUILD_DEFCONFIG := haps_hs_smp_defconfig
+
+ifeq ($(CROSS_COMPILE),)
+CROSS_COMPILE := $(call cc-cross-prefix, arc-linux- arceb-linux- arc-linux-gnu-)
+endif
+
+cflags-y	+= -fno-common -pipe -fno-builtin -mmedium-calls -mswape -D__linux__
+
+tune-mcpu-def-$(CONFIG_ISA_ARCOMPACT)	:= -mcpu=arc700
+tune-mcpu-def-$(CONFIG_ISA_ARCV2)	:= -mcpu=hs38
+
+ifeq ($(CONFIG_ARC_TUNE_MCPU),)
+cflags-y				+= $(tune-mcpu-def-y)
+else
+tune-mcpu				:= $(CONFIG_ARC_TUNE_MCPU)
+ifneq ($(call cc-option,$(tune-mcpu)),)
+cflags-y				+= $(tune-mcpu)
+else
+# The flag provided by 'CONFIG_ARC_TUNE_MCPU' option isn't known by this compiler
+# (probably the compiler is too old). Use ISA default mcpu flag instead as a safe option.
+$(warning ** WARNING ** CONFIG_ARC_TUNE_MCPU flag '$(tune-mcpu)' is unknown, fallback to '$(tune-mcpu-def-y)')
+cflags-y				+= $(tune-mcpu-def-y)
+endif
+endif
+
+ifdef CONFIG_ARC_CURR_IN_REG
+# For a global register definition, make sure it gets passed to every file
+# We had a customer reported bug where some code built in kernel was NOT using
+# any kernel headers, and missing the global register
+# Can't do unconditionally because of recursive include issues
+# due to <linux/thread_info.h>
+LINUXINCLUDE	+=  -include $(srctree)/arch/arc/include/asm/current.h
+cflags-y	+= -ffixed-gp
+endif
+
+cflags-y				+= -fsection-anchors
+
+cflags-$(CONFIG_ARC_HAS_LLSC)		+= -mlock
+
+ifdef CONFIG_ISA_ARCV2
+
+ifdef CONFIG_ARC_USE_UNALIGNED_MEM_ACCESS
+cflags-y				+= -munaligned-access
+else
+cflags-y				+= -mno-unaligned-access
+endif
+
+ifndef CONFIG_ARC_HAS_LL64
+cflags-y				+= -mno-ll64
+endif
+
+ifndef CONFIG_ARC_HAS_DIV_REM
+cflags-y				+= -mno-div-rem
+endif
+
+endif
+
+cfi := $(call as-instr,.cfi_startproc\n.cfi_endproc,-DARC_DW2_UNWIND_AS_CFI)
+cflags-$(CONFIG_ARC_DW2_UNWIND)		+= -fasynchronous-unwind-tables $(cfi)
+
+# small data is default for elf32 tool-chain. If not usable, disable it
+# This also allows repurposing GP as scratch reg to gcc reg allocator
+disable_small_data := y
+cflags-$(disable_small_data)		+= -mno-sdata
+
+cflags-$(CONFIG_CPU_BIG_ENDIAN)		+= -mbig-endian
+ldflags-$(CONFIG_CPU_BIG_ENDIAN)	+= -EB
+
+LIBGCC	= $(shell $(CC) $(cflags-y) --print-libgcc-file-name)
+
+# Modules with short calls might break for calls into builtin-kernel
+KBUILD_CFLAGS_MODULE	+= -mlong-calls -mno-millicode
+
+# Finally dump eveything into kernel build system
+KBUILD_CFLAGS	+= $(cflags-y)
+KBUILD_AFLAGS	+= $(KBUILD_CFLAGS)
+KBUILD_LDFLAGS	+= $(ldflags-y)
+
+core-y				+= arch/arc/plat-sim/
+core-$(CONFIG_ARC_PLAT_TB10X)	+= arch/arc/plat-tb10x/
+core-$(CONFIG_ARC_PLAT_AXS10X)	+= arch/arc/plat-axs10x/
+core-$(CONFIG_ARC_SOC_HSDK)	+= arch/arc/plat-hsdk/
+
+libs-y		+= arch/arc/lib/ $(LIBGCC)
+
+boot		:= arch/arc/boot
+
+boot_targets := uImage.bin uImage.gz uImage.lzma
+
+PHONY += $(boot_targets)
+$(boot_targets): vmlinux
+	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
+
+uimage-default-y			:= uImage.bin
+uimage-default-$(CONFIG_KERNEL_GZIP)	:= uImage.gz
+uimage-default-$(CONFIG_KERNEL_LZMA)	:= uImage.lzma
+
+PHONY += uImage
+uImage: $(uimage-default-y)
+	@ln -sf $< $(boot)/uImage
+	@$(kecho) '  Image $(boot)/uImage is ready'
+
+CLEAN_FILES += $(boot)/uImage