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, 311 insertions, 0 deletions

diff --git a/arch/mips/dec/int-handler.S b/arch/mips/dec/int-handler.S
new file mode 100644
index 000000000..a0b439c90
--- /dev/null
+++ b/arch/mips/dec/int-handler.S
@@ -0,0 +1,311 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 1995, 1996, 1997 Paul M. Antoine and Harald Koerfgen
+ * Copyright (C) 2000, 2001, 2002, 2003, 2005  Maciej W. Rozycki
+ *
+ * Written by Ralf Baechle and Andreas Busse, modified for DECstation
+ * support by Paul Antoine and Harald Koerfgen.
+ *
+ * completely rewritten:
+ * Copyright (C) 1998 Harald Koerfgen
+ *
+ * Rewritten extensively for controller-driven IRQ support
+ * by Maciej W. Rozycki.
+ */
+
+#include <asm/addrspace.h>
+#include <asm/asm.h>
+#include <asm/mipsregs.h>
+#include <asm/regdef.h>
+#include <asm/stackframe.h>
+
+#include <asm/dec/interrupts.h>
+#include <asm/dec/ioasic_addrs.h>
+#include <asm/dec/ioasic_ints.h>
+#include <asm/dec/kn01.h>
+#include <asm/dec/kn02.h>
+#include <asm/dec/kn02xa.h>
+#include <asm/dec/kn03.h>
+
+#define KN02_CSR_BASE		CKSEG1ADDR(KN02_SLOT_BASE + KN02_CSR)
+#define KN02XA_IOASIC_BASE	CKSEG1ADDR(KN02XA_SLOT_BASE + IOASIC_IOCTL)
+#define KN03_IOASIC_BASE	CKSEG1ADDR(KN03_SLOT_BASE + IOASIC_IOCTL)
+
+		.text
+		.set	noreorder
+/*
+ * plat_irq_dispatch: Interrupt handler for DECstations
+ *
+ * We follow the model in the Indy interrupt code by David Miller, where he
+ * says: a lot of complication here is taken away because:
+ *
+ * 1) We handle one interrupt and return, sitting in a loop
+ *    and moving across all the pending IRQ bits in the cause
+ *    register is _NOT_ the answer, the common case is one
+ *    pending IRQ so optimize in that direction.
+ *
+ * 2) We need not check against bits in the status register
+ *    IRQ mask, that would make this routine slow as hell.
+ *
+ * 3) Linux only thinks in terms of all IRQs on or all IRQs
+ *    off, nothing in between like BSD spl() brain-damage.
+ *
+ * Furthermore, the IRQs on the DECstations look basically (barring
+ * software IRQs which we don't use at all) like...
+ *
+ * DS2100/3100's, aka kn01, aka Pmax:
+ *
+ *	MIPS IRQ	Source
+ *	--------	------
+ *	       0	Software (ignored)
+ *	       1	Software (ignored)
+ *	       2	SCSI
+ *	       3	Lance Ethernet
+ *	       4	DZ11 serial
+ *	       5	RTC
+ *	       6	Memory Controller & Video
+ *	       7	FPU
+ *
+ * DS5000/200, aka kn02, aka 3max:
+ *
+ *	MIPS IRQ	Source
+ *	--------	------
+ *	       0	Software (ignored)
+ *	       1	Software (ignored)
+ *	       2	TurboChannel
+ *	       3	RTC
+ *	       4	Reserved
+ *	       5	Memory Controller
+ *	       6	Reserved
+ *	       7	FPU
+ *
+ * DS5000/1xx's, aka kn02ba, aka 3min:
+ *
+ *	MIPS IRQ	Source
+ *	--------	------
+ *	       0	Software (ignored)
+ *	       1	Software (ignored)
+ *	       2	TurboChannel Slot 0
+ *	       3	TurboChannel Slot 1
+ *	       4	TurboChannel Slot 2
+ *	       5	TurboChannel Slot 3 (ASIC)
+ *	       6	Halt button
+ *	       7	FPU/R4k timer
+ *
+ * DS5000/2x's, aka kn02ca, aka maxine:
+ *
+ *	MIPS IRQ	Source
+ *	--------	------
+ *	       0	Software (ignored)
+ *	       1	Software (ignored)
+ *	       2	Periodic Interrupt (100usec)
+ *	       3	RTC
+ *	       4	I/O write timeout
+ *	       5	TurboChannel (ASIC)
+ *	       6	Halt Keycode from Access.Bus keyboard (CTRL-ALT-ENTER)
+ *	       7	FPU/R4k timer
+ *
+ * DS5000/2xx's, aka kn03, aka 3maxplus:
+ *
+ *	MIPS IRQ	Source
+ *	--------	------
+ *	       0	Software (ignored)
+ *	       1	Software (ignored)
+ *	       2	System Board (ASIC)
+ *	       3	RTC
+ *	       4	Reserved
+ *	       5	Memory
+ *	       6	Halt Button
+ *	       7	FPU/R4k timer
+ *
+ * We handle the IRQ according to _our_ priority (see setup.c),
+ * then we just return.  If multiple IRQs are pending then we will
+ * just take another exception, big deal.
+ */
+		.align	5
+		NESTED(plat_irq_dispatch, PT_SIZE, ra)
+		.set	noreorder
+
+		/*
+		 * Get pending Interrupts
+		 */
+		mfc0	t0,CP0_CAUSE		# get pending interrupts
+		mfc0	t1,CP0_STATUS
+#if defined(CONFIG_32BIT) && defined(CONFIG_MIPS_FP_SUPPORT)
+		lw	t2,cpu_fpu_mask
+#endif
+		andi	t0,ST0_IM		# CAUSE.CE may be non-zero!
+		and	t0,t1			# isolate allowed ones
+
+		beqz	t0,spurious
+
+#if defined(CONFIG_32BIT) && defined(CONFIG_MIPS_FP_SUPPORT)
+		 and	t2,t0
+		bnez	t2,fpu			# handle FPU immediately
+#endif
+
+		/*
+		 * Find irq with highest priority
+		 */
+		# open coded PTR_LA t1, cpu_mask_nr_tbl
+#if defined(CONFIG_32BIT) || defined(KBUILD_64BIT_SYM32)
+		# open coded la t1, cpu_mask_nr_tbl
+		lui	t1, %hi(cpu_mask_nr_tbl)
+		addiu	t1, %lo(cpu_mask_nr_tbl)
+#else
+#error GCC `-msym32' option required for 64-bit DECstation builds
+#endif
+1:		lw	t2,(t1)
+		nop
+		and	t2,t0
+		beqz	t2,1b
+		 addu	t1,2*PTRSIZE		# delay slot
+
+		/*
+		 * Do the low-level stuff
+		 */
+		lw	a0,(-PTRSIZE)(t1)
+		nop
+		bgez	a0,handle_it		# irq_nr >= 0?
+						# irq_nr < 0: it is an address
+		 nop
+		jr	a0
+						# a trick to save a branch:
+		 lui	t2,(KN03_IOASIC_BASE>>16)&0xffff
+						# upper part of IOASIC Address
+
+/*
+ * Handle "IRQ Controller" Interrupts
+ * Masked Interrupts are still visible and have to be masked "by hand".
+ */
+		FEXPORT(kn02_io_int)		# 3max
+		lui	t0,(KN02_CSR_BASE>>16)&0xffff
+						# get interrupt status and mask
+		lw	t0,(t0)
+		nop
+		andi	t1,t0,KN02_IRQ_ALL
+		b	1f
+		 srl	t0,16			# shift interrupt mask
+
+		FEXPORT(kn02xa_io_int)		# 3min/maxine
+		lui	t2,(KN02XA_IOASIC_BASE>>16)&0xffff
+						# upper part of IOASIC Address
+
+		FEXPORT(kn03_io_int)		# 3max+ (t2 loaded earlier)
+		lw	t0,IO_REG_SIR(t2)	# get status: IOASIC sir
+		lw	t1,IO_REG_SIMR(t2)	# get mask:   IOASIC simr
+		nop
+
+1:		and	t0,t1			# mask out allowed ones
+
+		beqz	t0,spurious
+
+		/*
+		 * Find irq with highest priority
+		 */
+		# open coded PTR_LA t1,asic_mask_nr_tbl
+#if defined(CONFIG_32BIT) || defined(KBUILD_64BIT_SYM32)
+		# open coded la t1, asic_mask_nr_tbl
+		lui	t1, %hi(asic_mask_nr_tbl)
+		addiu	t1, %lo(asic_mask_nr_tbl)
+#else
+#error GCC `-msym32' option required for 64-bit DECstation builds
+#endif
+2:		lw	t2,(t1)
+		nop
+		and	t2,t0
+		beq	zero,t2,2b
+		 addu	t1,2*PTRSIZE		# delay slot
+
+		/*
+		 * Do the low-level stuff
+		 */
+		lw	a0,%lo(-PTRSIZE)(t1)
+		nop
+		bgez	a0,handle_it		# irq_nr >= 0?
+						# irq_nr < 0: it is an address
+		 nop
+		jr	a0
+		 nop				# delay slot
+
+/*
+ * Dispatch low-priority interrupts.  We reconsider all status
+ * bits again, which looks like a lose, but it makes the code
+ * simple and O(log n), so it gets compensated.
+ */
+		FEXPORT(cpu_all_int)		# HALT, timers, software junk
+		li	a0,DEC_CPU_IRQ_BASE
+		srl	t0,CAUSEB_IP
+		li	t1,CAUSEF_IP>>CAUSEB_IP	# mask
+		b	1f
+		 li	t2,4			# nr of bits / 2
+
+		FEXPORT(kn02_all_int)		# impossible ?
+		li	a0,KN02_IRQ_BASE
+		li	t1,KN02_IRQ_ALL		# mask
+		b	1f
+		 li	t2,4			# nr of bits / 2
+
+		FEXPORT(asic_all_int)		# various I/O ASIC junk
+		li	a0,IO_IRQ_BASE
+		li	t1,IO_IRQ_ALL		# mask
+		b	1f
+		 li	t2,8			# nr of bits / 2
+
+/*
+ * Dispatch DMA interrupts -- O(log n).
+ */
+		FEXPORT(asic_dma_int)		# I/O ASIC DMA events
+		li	a0,IO_IRQ_BASE+IO_INR_DMA
+		srl	t0,IO_INR_DMA
+		li	t1,IO_IRQ_DMA>>IO_INR_DMA # mask
+		li	t2,8			# nr of bits / 2
+
+		/*
+		 * Find irq with highest priority.
+		 * Highest irq number takes precedence.
+		 */
+1:		srlv	t3,t1,t2
+2:		xor	t1,t3
+		and	t3,t0,t1
+		beqz	t3,3f
+		 nop
+		move	t0,t3
+		addu	a0,t2
+3:		srl	t2,1
+		bnez	t2,2b
+		 srlv	t3,t1,t2
+
+handle_it:
+		j	do_IRQ
+		 nop
+
+#if defined(CONFIG_32BIT) && defined(CONFIG_MIPS_FP_SUPPORT)
+fpu:
+		lw	t0,fpu_kstat_irq
+		nop
+		lw	t1,(t0)
+		nop
+		addu	t1,1
+		j	handle_fpe_int
+		 sw	t1,(t0)
+#endif
+
+spurious:
+		j	spurious_interrupt
+		 nop
+		END(plat_irq_dispatch)
+
+/*
+ * Generic unimplemented interrupt routines -- cpu_mask_nr_tbl
+ * and asic_mask_nr_tbl are initialized to point all interrupts here.
+ * The tables are then filled in by machine-specific initialisation
+ * in dec_setup().
+ */
+		FEXPORT(dec_intr_unimplemented)
+		move	a1,t0			# cheats way of printing an arg!
+		ASM_PANIC("Unimplemented cpu interrupt! CP0_CAUSE: 0x%08x");
+
+		FEXPORT(asic_intr_unimplemented)
+		move	a1,t0			# cheats way of printing an arg!
+		ASM_PANIC("Unimplemented asic interrupt! ASIC ISR: 0x%08x");