tile: support CONFIG_PREEMPT

This change adds support for CONFIG_PREEMPT (full kernel preemption).
In addition to the core support, this change includes a number
of places where we fix up uses of smp_processor_id() and per-cpu
variables.  I also eliminate the PAGE_HOME_HERE and PAGE_HOME_UNKNOWN
values for page homing, as it turns out they weren't being used.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

9 files changed, 67 insertions, 29 deletions

diff --git a/arch/tile/kernel/asm-offsets.c b/arch/tile/kernel/asm-offsets.c
index 8652b0be4685..97ea6ac0a47b 100644
--- a/arch/tile/kernel/asm-offsets.c
+++ b/arch/tile/kernel/asm-offsets.c
@@ -58,6 +58,8 @@ void foo(void)
 	       offsetof(struct thread_info, status));
 	DEFINE(THREAD_INFO_HOMECACHE_CPU_OFFSET,
 	       offsetof(struct thread_info, homecache_cpu));
+	DEFINE(THREAD_INFO_PREEMPT_COUNT_OFFSET,
+	       offsetof(struct thread_info, preempt_count));
 	DEFINE(THREAD_INFO_STEP_STATE_OFFSET,
 	       offsetof(struct thread_info, step_state));
 #ifdef __tilegx__
diff --git a/arch/tile/kernel/hardwall.c b/arch/tile/kernel/hardwall.c
index 7db8893d4fc5..df27a1fd94a3 100644
--- a/arch/tile/kernel/hardwall.c
+++ b/arch/tile/kernel/hardwall.c
@@ -272,9 +272,9 @@ static void hardwall_setup_func(void *info)
 	struct hardwall_info *r = info;
 	struct hardwall_type *hwt = r->type;
 
-	int cpu = smp_processor_id();
-	int x = cpu % smp_width;
-	int y = cpu / smp_width;
+	int cpu = smp_processor_id();  /* on_each_cpu disables preemption */
+	int x = cpu_x(cpu);
+	int y = cpu_y(cpu);
 	int bits = 0;
 	if (x == r->ulhc_x)
 		bits |= W_PROTECT;
@@ -317,6 +317,7 @@ static void hardwall_protect_rectangle(struct hardwall_info *r)
 	on_each_cpu_mask(&rect_cpus, hardwall_setup_func, r, 1);
 }
 
+/* Entered from INT_xDN_FIREWALL interrupt vector with irqs disabled. */
 void __kprobes do_hardwall_trap(struct pt_regs* regs, int fault_num)
 {
 	struct hardwall_info *rect;
@@ -325,7 +326,6 @@ void __kprobes do_hardwall_trap(struct pt_regs* regs, int fault_num)
 	struct siginfo info;
 	int cpu = smp_processor_id();
 	int found_processes;
-	unsigned long flags;
 	struct pt_regs *old_regs = set_irq_regs(regs);
 
 	irq_enter();
@@ -346,7 +346,7 @@ void __kprobes do_hardwall_trap(struct pt_regs* regs, int fault_num)
 	BUG_ON(hwt->disabled);
 
 	/* This tile trapped a network access; find the rectangle. */
-	spin_lock_irqsave(&hwt->lock, flags);
+	spin_lock(&hwt->lock);
 	list_for_each_entry(rect, &hwt->list, list) {
 		if (cpumask_test_cpu(cpu, &rect->cpumask))
 			break;
@@ -401,7 +401,7 @@ void __kprobes do_hardwall_trap(struct pt_regs* regs, int fault_num)
 		pr_notice("hardwall: no associated processes!\n");
 
  done:
-	spin_unlock_irqrestore(&hwt->lock, flags);
+	spin_unlock(&hwt->lock);
 
 	/*
 	 * We have to disable firewall interrupts now, or else when we
@@ -661,7 +661,7 @@ static int hardwall_deactivate(struct hardwall_type *hwt,
 		return -EINVAL;
 
 	printk(KERN_DEBUG "Pid %d (%s) deactivated for %s hardwall: cpu %d\n",
-	       task->pid, task->comm, hwt->name, smp_processor_id());
+	       task->pid, task->comm, hwt->name, raw_smp_processor_id());
 	return 0;
 }
 
@@ -803,8 +803,8 @@ static void reset_xdn_network_state(struct hardwall_type *hwt)
 	/* Reset UDN coordinates to their standard value */
 	{
 		unsigned int cpu = smp_processor_id();
-		unsigned int x = cpu % smp_width;
-		unsigned int y = cpu / smp_width;
+		unsigned int x = cpu_x(cpu);
+		unsigned int y = cpu_y(cpu);
 		__insn_mtspr(SPR_UDN_TILE_COORD, (x << 18) | (y << 7));
 	}
 
diff --git a/arch/tile/kernel/intvec_32.S b/arch/tile/kernel/intvec_32.S
index 388061319c4c..10767655689e 100644
--- a/arch/tile/kernel/intvec_32.S
+++ b/arch/tile/kernel/intvec_32.S
@@ -28,10 +28,6 @@
 #include <arch/interrupts.h>
 #include <arch/spr_def.h>
 
-#ifdef CONFIG_PREEMPT
-# error "No support for kernel preemption currently"
-#endif
-
 #define PTREGS_PTR(reg, ptreg) addli reg, sp, C_ABI_SAVE_AREA_SIZE + (ptreg)
 
 #define PTREGS_OFFSET_SYSCALL PTREGS_OFFSET_REG(TREG_SYSCALL_NR)
@@ -812,17 +808,34 @@ STD_ENTRY(interrupt_return)
 	}
 	lw      r29, r29
 	andi    r29, r29, SPR_EX_CONTEXT_1_1__PL_MASK  /* mask off ICS */
+	bzt     r29, .Lresume_userspace
+
+#ifdef CONFIG_PREEMPT
+	/* Returning to kernel space. Check if we need preemption. */
+	GET_THREAD_INFO(r29)
+	addli   r28, r29, THREAD_INFO_FLAGS_OFFSET
 	{
-	 bzt    r29, .Lresume_userspace
-	 PTREGS_PTR(r29, PTREGS_OFFSET_PC)
+	 lw     r28, r28
+	 addli  r29, r29, THREAD_INFO_PREEMPT_COUNT_OFFSET
+	}
+	{
+	 andi   r28, r28, _TIF_NEED_RESCHED
+	 lw     r29, r29
 	}
+	bzt     r28, 1f
+	bnz     r29, 1f
+	jal     preempt_schedule_irq
+	FEEDBACK_REENTER(interrupt_return)
+1:
+#endif
 
 	/* If we're resuming to _cpu_idle_nap, bump PC forward by 8. */
 	{
-	 lw     r28, r29
+	 PTREGS_PTR(r29, PTREGS_OFFSET_PC)
 	 moveli r27, lo16(_cpu_idle_nap)
 	}
 	{
+	 lw     r28, r29
 	 auli   r27, r27, ha16(_cpu_idle_nap)
 	}
 	{
diff --git a/arch/tile/kernel/intvec_64.S b/arch/tile/kernel/intvec_64.S
index 884af9ea5bed..38a60f27707c 100644
--- a/arch/tile/kernel/intvec_64.S
+++ b/arch/tile/kernel/intvec_64.S
@@ -30,10 +30,6 @@
 #include <arch/interrupts.h>
 #include <arch/spr_def.h>
 
-#ifdef CONFIG_PREEMPT
-# error "No support for kernel preemption currently"
-#endif
-
 #define PTREGS_PTR(reg, ptreg) addli reg, sp, C_ABI_SAVE_AREA_SIZE + (ptreg)
 
 #define PTREGS_OFFSET_SYSCALL PTREGS_OFFSET_REG(TREG_SYSCALL_NR)
@@ -820,11 +816,33 @@ STD_ENTRY(interrupt_return)
 	andi    r29, r29, SPR_EX_CONTEXT_1_1__PL_MASK  /* mask off ICS */
 	{
 	 beqzt  r29, .Lresume_userspace
-	 PTREGS_PTR(r29, PTREGS_OFFSET_PC)
+	 move   r29, sp
+	}
+
+#ifdef CONFIG_PREEMPT
+	/* Returning to kernel space. Check if we need preemption. */
+	EXTRACT_THREAD_INFO(r29)
+	addli   r28, r29, THREAD_INFO_FLAGS_OFFSET
+	{
+	 ld     r28, r28
+	 addli  r29, r29, THREAD_INFO_PREEMPT_COUNT_OFFSET
 	}
+	{
+	 andi   r28, r28, _TIF_NEED_RESCHED
+	 ld4s   r29, r29
+	}
+	beqzt   r28, 1f
+	bnez    r29, 1f
+	jal     preempt_schedule_irq
+	FEEDBACK_REENTER(interrupt_return)
+1:
+#endif
 
 	/* If we're resuming to _cpu_idle_nap, bump PC forward by 8. */
-	moveli  r27, hw2_last(_cpu_idle_nap)
+	{
+	 moveli r27, hw2_last(_cpu_idle_nap)
+	 PTREGS_PTR(r29, PTREGS_OFFSET_PC)
+	}
 	{
 	 ld     r28, r29
 	 shl16insli r27, r27, hw1(_cpu_idle_nap)
diff --git a/arch/tile/kernel/irq.c b/arch/tile/kernel/irq.c
index 02e628065012..c90de6c3cb7f 100644
--- a/arch/tile/kernel/irq.c
+++ b/arch/tile/kernel/irq.c
@@ -74,6 +74,7 @@ static DEFINE_SPINLOCK(available_irqs_lock);
 /*
  * The interrupt handling path, implemented in terms of HV interrupt
  * emulation on TILE64 and TILEPro, and IPI hardware on TILE-Gx.
+ * Entered with interrupts disabled.
  */
 void tile_dev_intr(struct pt_regs *regs, int intnum)
 {
diff --git a/arch/tile/kernel/smp.c b/arch/tile/kernel/smp.c
index cbc73a8b8fe1..6cc520d71d2b 100644
--- a/arch/tile/kernel/smp.c
+++ b/arch/tile/kernel/smp.c
@@ -100,8 +100,8 @@ static void smp_start_cpu_interrupt(void)
 /* Handler to stop the current cpu. */
 static void smp_stop_cpu_interrupt(void)
 {
-	set_cpu_online(smp_processor_id(), 0);
 	arch_local_irq_disable_all();
+	set_cpu_online(smp_processor_id(), 0);
 	for (;;)
 		asm("nap; nop");
 }
diff --git a/arch/tile/kernel/smpboot.c b/arch/tile/kernel/smpboot.c
index 44bab29bf2f3..dee7f13c5854 100644
--- a/arch/tile/kernel/smpboot.c
+++ b/arch/tile/kernel/smpboot.c
@@ -142,13 +142,15 @@ static struct cpumask cpu_started __cpuinitdata;
  */
 static void __cpuinit start_secondary(void)
 {
-	int cpuid = smp_processor_id();
+	int cpuid;
+
+	preempt_disable();
+
+	cpuid = smp_processor_id();
 
 	/* Set our thread pointer appropriately. */
 	set_my_cpu_offset(__per_cpu_offset[cpuid]);
 
-	preempt_disable();
-
 	/*
 	 * In large machines even this will slow us down, since we
 	 * will be contending for for the printk spinlock.
diff --git a/arch/tile/kernel/stack.c b/arch/tile/kernel/stack.c
index c972689231ef..176ffe48eee9 100644
--- a/arch/tile/kernel/stack.c
+++ b/arch/tile/kernel/stack.c
@@ -194,7 +194,7 @@ static int KBacktraceIterator_next_item_inclusive(
  */
 static void validate_stack(struct pt_regs *regs)
 {
-	int cpu = smp_processor_id();
+	int cpu = raw_smp_processor_id();
 	unsigned long ksp0 = get_current_ksp0();
 	unsigned long ksp0_base = ksp0 - THREAD_SIZE;
 	unsigned long sp = stack_pointer;
@@ -392,7 +392,7 @@ void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
 		pr_err("Starting stack dump of tid %d, pid %d (%s)"
 		       " on cpu %d at cycle %lld\n",
 		       kbt->task->pid, kbt->task->tgid, kbt->task->comm,
-		       smp_processor_id(), get_cycles());
+		       raw_smp_processor_id(), get_cycles());
 	}
 	kbt->verbose = 1;
 	i = 0;
diff --git a/arch/tile/kernel/sys.c b/arch/tile/kernel/sys.c
index b881a7be24bd..38debe706061 100644
--- a/arch/tile/kernel/sys.c
+++ b/arch/tile/kernel/sys.c
@@ -38,8 +38,10 @@
 SYSCALL_DEFINE3(cacheflush, unsigned long, addr, unsigned long, len,
 		unsigned long, flags)
 {
+	/* DCACHE is not particularly effective if not bound to one cpu. */
 	if (flags & DCACHE)
-		homecache_evict(cpumask_of(smp_processor_id()));
+		homecache_evict(cpumask_of(raw_smp_processor_id()));
+
 	if (flags & ICACHE)
 		flush_remote(0, HV_FLUSH_EVICT_L1I, mm_cpumask(current->mm),
 			     0, 0, 0, NULL, NULL, 0);