/**************************************************************************** * sched/irq/irq_csection.c * * Copyright (C) 2016 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name NuttX nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include "sched/sched.h" #include "irq/irq.h" #ifdef CONFIG_SMP /**************************************************************************** * Public Data ****************************************************************************/ /* This is the spinlock that enforces critical sections when interrupts are * disabled. */ volatile spinlock_t g_cpu_irqlock = SP_UNLOCKED; /* Used to keep track of which CPU(s) hold the IRQ lock. */ volatile spinlock_t g_cpu_irqsetlock; volatile cpu_set_t g_cpu_irqset; /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: enter_critical_section * * Description: * Take the CPU IRQ lock and disable interrupts on all CPUs. A thread- * specific counter is increment to indicate that the thread has IRQs * disabled and to support nested calls to enter_critical_section(). * ****************************************************************************/ irqstate_t enter_critical_section(void) { FAR struct tcb_s *rtcb; /* Do nothing if called from an interrupt handler */ if (up_interrupt_context()) { /* The value returned does not matter. We assume only that it is a * scalar here. */ return (irqstate_t)0; } /* Do we already have interrupts disabled? */ rtcb = this_task(); if (rtcb->irqcount > 0) { /* Yes... make sure that the spinlock is set and increment the IRQ * lock count. */ DEBUGASSERT(g_cpu_irqlock == SP_LOCKED && rtcb->irqcount < INT16_MAX); rtcb->irqcount++; } else { /* NO.. Take the spinlock to get exclusive access and set the lock * count to 1. * * We must avoid that case where a context occurs between taking the * g_cpu_irqlock and disabling interrupts. Also interrupts disables * must follow a stacked order. We cannot other context switches to * re-order the enabling/disabling of interrupts. * * The scheduler accomplishes this by treating the irqcount like * lockcount: Both will disable pre-emption. */ spin_setbit(&g_cpu_irqset, this_cpu(), &g_cpu_irqsetlock, &g_cpu_irqlock); rtcb->irqcount = 1; #ifdef CONFIG_SCHED_INSTRUMENTATION_CSECTION /* Note that we have entered the critical section */ sched_note_csection(rtcb, true); #endif } /* Then disable interrupts (they may already be disabled, be we need to * return valid interrupt status in any event). */ return up_irq_save(); } /**************************************************************************** * Name: leave_critical_section * * Description: * Decrement the IRQ lock count and if it decrements to zero then release * the spinlock. * ****************************************************************************/ void leave_critical_section(irqstate_t flags) { /* Do nothing if called from an interrupt handler */ if (!up_interrupt_context()) { FAR struct tcb_s *rtcb = this_task(); DEBUGASSERT(rtcb->irqcount > 0); /* Will we still have interrupts disabled after decrementing the * count? */ if (rtcb->irqcount > 1) { /* Yes... make sure that the spinlock is set */ DEBUGASSERT(g_cpu_irqlock == SP_LOCKED); rtcb->irqcount--; } else { #ifdef CONFIG_SCHED_INSTRUMENTATION_CSECTION /* No.. Note that we have entered the critical section */ sched_note_csection(rtcb, false); #endif /* Decrement our count on the lock. If all CPUs have released, * then unlock the spinlock. */ rtcb->irqcount = 0; spin_clrbit(&g_cpu_irqset, this_cpu(), &g_cpu_irqsetlock, &g_cpu_irqlock); /* Have all CPUs release the lock? */ if (!spin_islocked(&g_cpu_irqlock)) { /* Check if there are pending tasks and that pre-emption is * also enabled. */ if (g_pendingtasks.head != NULL && !spin_islocked(&g_cpu_schedlock)) { /* Release any ready-to-run tasks that have collected in * g_pendingtasks if the scheduler is not locked. * * NOTE: This operation has a very high likelihood of causing * this task to be switched out! */ up_release_pending(); } } } /* Restore the previous interrupt state which may still be interrupts * disabled (but we don't have a mechanism to verify that now) */ up_irq_restore(flags); } } #endif /* CONFIG_SMP */