/**
* preempt_schedule_context - preempt_schedule called by tracing
*
* The tracing infrastructure uses preempt_enable_notrace to prevent
* recursion and tracing preempt enabling caused by the tracing
* infrastructure itself. But as tracing can happen in areas coming
* from userspace or just about to enter userspace, a preempt enable
* can occur before user_exit() is called. This will cause the scheduler
* to be called when the system is still in usermode.
*
* To prevent this, the preempt_enable_notrace will use this function
* instead of preempt_schedule() to exit user context if needed before
* calling the scheduler.
*/
asmlinkage void __sched notrace preempt_schedule_context(void)
{
enum ctx_state prev_ctx;
if (likely(!preemptible()))
return;
/*
* Need to disable preemption in case user_exit() is traced
* and the tracer calls preempt_enable_notrace() causing
* an infinite recursion.
*/
preempt_disable_notrace();
prev_ctx = exception_enter();
preempt_enable_no_resched_notrace();
preempt_schedule();
preempt_disable_notrace();
exception_exit(prev_ctx);
preempt_enable_notrace();
}
/*
* do_IRQ handles all normal device IRQ's (the special
* SMP cross-CPU interrupts have their own specific
* handlers).
*/
asmlinkage unsigned int __noinstrument do_IRQ(int irq, struct pt_regs *regs)
{
/*
* We ack quickly, we don't want the irq controller
* thinking we're snobs just because some other CPU has
* disabled global interrupts (we have already done the
* INT_ACK cycles, it's too late to try to pretend to the
* controller that we aren't taking the interrupt).
*
* 0 return value means that this irq is already being
* handled by some other CPU. (or is disabled)
*/
int cpu = smp_processor_id();
irq_desc_t *desc = irq_desc + irq;
struct irqaction * action;
unsigned int status;
#ifdef CONFIG_ILATENCY
{
extern void interrupt_overhead_start(void);
interrupt_overhead_start();
}
#endif /* CONFIG_ILATENCY */
preempt_disable();
TRACE_IRQ_ENTRY(irq, !user_mode(regs));
kstat.irqs[cpu][irq]++;
spin_lock(&desc->lock);
desc->handler->ack(irq);
/*
REPLAY is when Linux resends an IRQ that was dropped earlier
WAITING is used by probe to mark irqs that are being tested
*/
status = desc->status & ~(IRQ_REPLAY | IRQ_WAITING);
status |= IRQ_PENDING; /* we _want_ to handle it */
/*
* If the IRQ is disabled for whatever reason, we cannot
* use the action we have.
*/
action = NULL;
if (!(status & (IRQ_DISABLED | IRQ_INPROGRESS))) {
action = desc->action;
status &= ~IRQ_PENDING; /* we commit to handling */
status |= IRQ_INPROGRESS; /* we are handling it */
}
desc->status = status;
/*
* If there is no IRQ handler or it was disabled, exit early.
Since we set PENDING, if another processor is handling
a different instance of this same irq, the other processor
will take care of it.
*/
if (!action)
goto out;
/*
* Edge triggered interrupts need to remember
* pending events.
* This applies to any hw interrupts that allow a second
* instance of the same irq to arrive while we are in do_IRQ
* or in the handler. But the code here only handles the _second_
* instance of the irq, not the third or fourth. So it is mostly
* useful for irq hardware that does not mask cleanly in an
* SMP environment.
*/
#ifdef CONFIG_ILATENCY
{
extern void interrupt_overhead_stop(void);
interrupt_overhead_stop();
}
#endif /* CONFIG_ILATENCY */
for (;;) {
spin_unlock(&desc->lock);
handle_IRQ_event(irq, regs, action);
spin_lock(&desc->lock);
if (!(desc->status & IRQ_PENDING))
break;
desc->status &= ~IRQ_PENDING;
}
desc->status &= ~IRQ_INPROGRESS;
out:
/*
* The ->end() handler has to deal with interrupts which got
* disabled while the handler was running.
*/
desc->handler->end(irq);
spin_unlock(&desc->lock);
TRACE_IRQ_EXIT();
if (softirq_pending(cpu))
do_softirq();
#if defined(CONFIG_PREEMPT)
for(;;) {
preempt_enable_no_resched();
if (preempt_is_disabled() || !need_resched())
break;
db_assert(intr_off());
db_assert(!in_interrupt());
preempt_disable();
__sti();
preempt_schedule();
__cli();
}
#endif
#ifdef CONFIG_ILATENCY
intr_ret_from_exception();
#endif
return 1;
}
