schedule(): do not preempt while holding spinlocks or while in offloaded syscall

arch/x86/kernel/include/arch-lock.h

@@ -14,6 +14,9 @@ int __kprintf(const char *format, ...);
 
 typedef int ihk_spinlock_t;
 
+extern void preempt_enable(void);
+extern void preempt_disable(void);
+
 #define IHK_STATIC_SPINLOCK_FUNCS
 
 static void ihk_mc_spinlock_init(ihk_spinlock_t *lock)
@@ -45,6 +48,9 @@ static void ihk_mc_spinlock_lock_noirq(ihk_spinlock_t *lock)
 	__kprintf("[%d] trying to grab lock: 0x%lX\n", 
 	          ihk_mc_get_processor_id(), lock);
 #endif
+
+	preempt_disable();
+
 	asm volatile("lock; xaddl %0, %1\n"
 			"movzwl %w0, %2\n\t"
 			"shrl $16, %0\n\t"
@@ -79,6 +85,8 @@ static unsigned long ihk_mc_spinlock_lock(ihk_spinlock_t *lock)
 static void ihk_mc_spinlock_unlock_noirq(ihk_spinlock_t *lock)
 {
 	asm volatile ("lock incw %0" : "+m"(*lock) : : "memory", "cc");
+	
+	preempt_enable();
 }
 
 static void ihk_mc_spinlock_unlock(ihk_spinlock_t *lock, unsigned long flags)

kernel/cls.c

@@ -23,6 +23,7 @@
 extern int num_processors;
 
 struct cpu_local_var *clv;
+static int cpu_local_var_initialized = 0;
 
 void cpu_local_var_init(void)
 {
@@ -33,9 +34,22 @@ void cpu_local_var_init(void)
 
 	clv = allocate_pages(z, IHK_MC_AP_CRITICAL);
 	memset(clv, 0, z * PAGE_SIZE);
+	cpu_local_var_initialized = 1;
 }
 
 struct cpu_local_var *get_cpu_local_var(int id)
 {
 	return clv + id;
 }
+
+void preempt_enable(void)
+{
+	if (cpu_local_var_initialized)
+		--cpu_local_var(no_preempt);
+}
+
+void preempt_disable(void)
+{
+	if (cpu_local_var_initialized)
+		++cpu_local_var(no_preempt);
+}

kernel/include/cls.h

@@ -68,6 +68,7 @@ struct cpu_local_var {
 	ihk_spinlock_t migq_lock;
 	struct list_head migq;
 	int in_interrupt;
+	int no_preempt;
 } __attribute__((aligned(64)));
 
 

kernel/include/process.h

@@ -411,6 +411,7 @@ struct process {
 	fp_regs_struct *fp_regs;
 	char *saved_cmdline;
 	long saved_cmdline_len;
+	int in_syscall_offload;
 };
 
 struct process_vm {

kernel/mem.c

@@ -370,6 +370,8 @@ static void page_fault_handler(void *fault_addr, uint64_t reason, void *regs)
 	dkprintf("[%d]page_fault_handler(%p,%lx,%p)\n",
 			ihk_mc_get_processor_id(), fault_addr, reason, regs);
 
+	preempt_disable();
+
 	cpu_enable_interrupt();
 
 	error = page_fault_process_vm(proc->vm, fault_addr, reason);
@@ -422,6 +424,7 @@ static void page_fault_handler(void *fault_addr, uint64_t reason, void *regs)
 
 	error = 0;
 out:
+	preempt_enable();
 	dkprintf("[%d]page_fault_handler(%p,%lx,%p): (%d)\n",
 			ihk_mc_get_processor_id(), fault_addr, reason,
 			regs, error);

kernel/process.c

@@ -2225,6 +2225,16 @@ void schedule(void)
 	unsigned long irqstate;
 	struct process *last;
 
+	if (cpu_local_var(no_preempt)) {
+		dkprintf("no schedule() while no preemption! \n");
+		return;
+	}
+	
+	if (cpu_local_var(current)->in_syscall_offload) {
+		dkprintf("no schedule() while syscall offload!\n");
+		return;
+	}
+	
 redo:
 	irqstate = ihk_mc_spinlock_lock(&(get_this_cpu_local_var()->runq_lock));
 	v = get_this_cpu_local_var();

kernel/syscall.c

@@ -192,6 +192,7 @@ long do_syscall(struct syscall_request *req, int cpu, int pid)
 	unsigned long irqstate;
 	struct process *proc = cpu_local_var(current);
 
+	++proc->in_syscall_offload;
 	dkprintf("SC(%d)[%3d] sending syscall\n",
 	        ihk_mc_get_processor_id(),
 	        req->number);
@@ -252,6 +253,7 @@ long do_syscall(struct syscall_request *req, int cpu, int pid)
 		ihk_mc_spinlock_unlock(&syscall_lock, irqstate);
 	}
 
+	--proc->in_syscall_offload;
 	return rc;
 }