[PATCH] lockdep: irqtrace subsystem, core

Accurate hard-IRQ-flags and softirq-flags state tracing.

This allows us to attach extra functionality to IRQ flags on/off
events (such as trace-on/off).

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 140 insertions, 20 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 1cd46a4..b7db7fb 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -968,6 +968,10 @@ static task_t *copy_process(unsigned long clone_flags,
 	if (!p)
 		goto fork_out;
 
+#ifdef CONFIG_TRACE_IRQFLAGS
+	DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
+	DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
+#endif
 	retval = -EAGAIN;
 	if (atomic_read(&p->user->processes) >=
 			p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
@@ -1042,6 +1046,21 @@ static task_t *copy_process(unsigned long clone_flags,
  	}
 	mpol_fix_fork_child_flag(p);
 #endif
+#ifdef CONFIG_TRACE_IRQFLAGS
+	p->irq_events = 0;
+	p->hardirqs_enabled = 0;
+	p->hardirq_enable_ip = 0;
+	p->hardirq_enable_event = 0;
+	p->hardirq_disable_ip = _THIS_IP_;
+	p->hardirq_disable_event = 0;
+	p->softirqs_enabled = 1;
+	p->softirq_enable_ip = _THIS_IP_;
+	p->softirq_enable_event = 0;
+	p->softirq_disable_ip = 0;
+	p->softirq_disable_event = 0;
+	p->hardirq_context = 0;
+	p->softirq_context = 0;
+#endif
 
 	rt_mutex_init_task(p);
 
diff --git a/kernel/sched.c b/kernel/sched.c
index 48c1faa..9118299 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4462,7 +4462,9 @@ int __sched cond_resched_softirq(void)
 	BUG_ON(!in_softirq());
 
 	if (need_resched() && __resched_legal()) {
-		__local_bh_enable();
+		raw_local_irq_disable();
+		_local_bh_enable();
+		raw_local_irq_enable();
 		__cond_resched();
 		local_bh_disable();
 		return 1;
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 8f03e3b..584609b 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -62,6 +62,119 @@ static inline void wakeup_softirqd(void)
 }
 
 /*
+ * This one is for softirq.c-internal use,
+ * where hardirqs are disabled legitimately:
+ */
+static void __local_bh_disable(unsigned long ip)
+{
+	unsigned long flags;
+
+	WARN_ON_ONCE(in_irq());
+
+	raw_local_irq_save(flags);
+	add_preempt_count(SOFTIRQ_OFFSET);
+	/*
+	 * Were softirqs turned off above:
+	 */
+	if (softirq_count() == SOFTIRQ_OFFSET)
+		trace_softirqs_off(ip);
+	raw_local_irq_restore(flags);
+}
+
+void local_bh_disable(void)
+{
+	__local_bh_disable((unsigned long)__builtin_return_address(0));
+}
+
+EXPORT_SYMBOL(local_bh_disable);
+
+void __local_bh_enable(void)
+{
+	WARN_ON_ONCE(in_irq());
+
+	/*
+	 * softirqs should never be enabled by __local_bh_enable(),
+	 * it always nests inside local_bh_enable() sections:
+	 */
+	WARN_ON_ONCE(softirq_count() == SOFTIRQ_OFFSET);
+
+	sub_preempt_count(SOFTIRQ_OFFSET);
+}
+EXPORT_SYMBOL_GPL(__local_bh_enable);
+
+/*
+ * Special-case - softirqs can safely be enabled in
+ * cond_resched_softirq(), or by __do_softirq(),
+ * without processing still-pending softirqs:
+ */
+void _local_bh_enable(void)
+{
+	WARN_ON_ONCE(in_irq());
+	WARN_ON_ONCE(!irqs_disabled());
+
+	if (softirq_count() == SOFTIRQ_OFFSET)
+		trace_softirqs_on((unsigned long)__builtin_return_address(0));
+	sub_preempt_count(SOFTIRQ_OFFSET);
+}
+
+EXPORT_SYMBOL(_local_bh_enable);
+
+void local_bh_enable(void)
+{
+	unsigned long flags;
+
+	WARN_ON_ONCE(in_irq());
+	WARN_ON_ONCE(irqs_disabled());
+
+	local_irq_save(flags);
+	/*
+	 * Are softirqs going to be turned on now:
+	 */
+	if (softirq_count() == SOFTIRQ_OFFSET)
+		trace_softirqs_on((unsigned long)__builtin_return_address(0));
+	/*
+	 * Keep preemption disabled until we are done with
+	 * softirq processing:
+ 	 */
+ 	sub_preempt_count(SOFTIRQ_OFFSET - 1);
+
+	if (unlikely(!in_interrupt() && local_softirq_pending()))
+		do_softirq();
+
+	dec_preempt_count();
+	local_irq_restore(flags);
+	preempt_check_resched();
+}
+EXPORT_SYMBOL(local_bh_enable);
+
+void local_bh_enable_ip(unsigned long ip)
+{
+	unsigned long flags;
+
+	WARN_ON_ONCE(in_irq());
+
+	local_irq_save(flags);
+	/*
+	 * Are softirqs going to be turned on now:
+	 */
+	if (softirq_count() == SOFTIRQ_OFFSET)
+		trace_softirqs_on(ip);
+	/*
+	 * Keep preemption disabled until we are done with
+	 * softirq processing:
+ 	 */
+ 	sub_preempt_count(SOFTIRQ_OFFSET - 1);
+
+	if (unlikely(!in_interrupt() && local_softirq_pending()))
+		do_softirq();
+
+	dec_preempt_count();
+	local_irq_restore(flags);
+	preempt_check_resched();
+}
+EXPORT_SYMBOL(local_bh_enable_ip);
+
+/*
  * We restart softirq processing MAX_SOFTIRQ_RESTART times,
  * and we fall back to softirqd after that.
  *
@@ -80,8 +193,9 @@ asmlinkage void __do_softirq(void)
 	int cpu;
 
 	pending = local_softirq_pending();
+	__local_bh_disable((unsigned long)__builtin_return_address(0));
+	trace_softirq_enter();
 
-	local_bh_disable();
 	cpu = smp_processor_id();
 restart:
 	/* Reset the pending bitmask before enabling irqs */
@@ -109,7 +223,8 @@ restart:
 	if (pending)
 		wakeup_softirqd();
 
-	__local_bh_enable();
+	trace_softirq_exit();
+	_local_bh_enable();
 }
 
 #ifndef __ARCH_HAS_DO_SOFTIRQ
@@ -136,23 +251,6 @@ EXPORT_SYMBOL(do_softirq);
 
 #endif
 
-void local_bh_enable(void)
-{
-	WARN_ON(irqs_disabled());
-	/*
-	 * Keep preemption disabled until we are done with
-	 * softirq processing:
- 	 */
- 	sub_preempt_count(SOFTIRQ_OFFSET - 1);
-
-	if (unlikely(!in_interrupt() && local_softirq_pending()))
-		do_softirq();
-
-	dec_preempt_count();
-	preempt_check_resched();
-}
-EXPORT_SYMBOL(local_bh_enable);
-
 #ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED
 # define invoke_softirq()	__do_softirq()
 #else
@@ -165,6 +263,7 @@ EXPORT_SYMBOL(local_bh_enable);
 void irq_exit(void)
 {
 	account_system_vtime(current);
+	trace_hardirq_exit();
 	sub_preempt_count(IRQ_EXIT_OFFSET);
 	if (!in_interrupt() && local_softirq_pending())
 		invoke_softirq();