x86: preempt-rt preparatory patches for x86 (32bit)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/include/asm/spinlock.h

@@ -298,9 +298,9 @@ static inline void __raw_write_unlock(raw_rwlock_t *rw)
 #define __raw_read_lock_flags(lock, flags) __raw_read_lock(lock)
 #define __raw_write_lock_flags(lock, flags) __raw_write_lock(lock)
 
-#define _raw_spin_relax(lock)	cpu_relax()
-#define _raw_read_relax(lock)	cpu_relax()
-#define _raw_write_relax(lock)	cpu_relax()
+#define __raw_spin_relax(lock)	cpu_relax()
+#define __raw_read_relax(lock)	cpu_relax()
+#define __raw_write_relax(lock)	cpu_relax()
 
 /* The {read|write|spin}_lock() on x86 are full memory barriers. */
 static inline void smp_mb__after_lock(void) { }

arch/x86/include/asm/tlbflush.h

@@ -17,7 +17,9 @@
 
 static inline void __native_flush_tlb(void)
 {
+	preempt_disable();
 	native_write_cr3(native_read_cr3());
+	preempt_enable();
 }
 
 static inline void __native_flush_tlb_global(void)

arch/x86/kernel/apic/nmi.c

@@ -90,7 +90,9 @@ static inline unsigned int get_timer_irqs(int cpu)
  */
 static __init void nmi_cpu_busy(void *data)
 {
+#ifndef CONFIG_PREEMPT_RT
 	local_irq_enable_in_hardirq();
+#endif
 	/*
 	 * Intentionally don't use cpu_relax here. This is
 	 * to make sure that the performance counter really ticks,

arch/x86/kernel/early_printk.c

@@ -881,7 +881,7 @@ static int __initdata early_console_initialized;
 
 asmlinkage void early_printk(const char *fmt, ...)
 {
-	char buf[512];
+	static char buf[512];
 	int n;
 	va_list ap;
 

arch/x86/kernel/head64.c

@@ -30,7 +30,11 @@ static void __init zap_identity_mappings(void)
 {
 	pgd_t *pgd = pgd_offset_k(0UL);
 	pgd_clear(pgd);
-	__flush_tlb_all();
+	/*
+	 * preempt_disable/enable does not work this early in the
+	 * bootup yet:
+	 */
+	write_cr3(read_cr3());
 }
 
 /* Don't add a printk in there. printk relies on the PDA which is not initialized 

arch/x86/kernel/process_64.c

@@ -152,9 +152,11 @@ void cpu_idle(void)
 		}
 
 		tick_nohz_restart_sched_tick();
+		local_irq_disable();
 		__preempt_enable_no_resched();
-		schedule();
+		__schedule();
 		preempt_disable();
+		local_irq_enable();
 	}
 }
 

arch/x86/kernel/signal.c

@@ -782,6 +782,13 @@ static void do_signal(struct pt_regs *regs)
 	int signr;
 	sigset_t *oldset;
 
+#ifdef CONFIG_PREEMPT_RT
+	/*
+	 * Fully-preemptible kernel does not need interrupts disabled:
+	 */
+	local_irq_enable();
+	preempt_check_resched();
+#endif
 	/*
 	 * We want the common case to go fast, which is why we may in certain
 	 * cases get here from kernel mode. Just return without doing anything

arch/x86/kernel/smp.c

@@ -120,6 +120,16 @@ static void native_smp_send_reschedule(int cpu)
 	apic->send_IPI_mask(cpumask_of(cpu), RESCHEDULE_VECTOR);
 }
 
+/*
+ * this function sends a 'reschedule' IPI to all other CPUs.
+ * This is used when RT tasks are starving and other CPUs
+ * might be able to run them:
+ */
+void smp_send_reschedule_allbutself(void)
+{
+	apic->send_IPI_allbutself(RESCHEDULE_VECTOR);
+}
+
 void native_send_call_func_single_ipi(int cpu)
 {
 	apic->send_IPI_mask(cpumask_of(cpu), CALL_FUNCTION_SINGLE_VECTOR);