e2df52390a
Situation:
Assume we have 2 cpus, and busy run task0.
CPU0 CPU1
task0 -> task1 task2 -> task0
1. remove task0 form runninglist
2. take task1 as new tcb
3. add task0 to blocklist
4. clear spinlock
4.1 remove task2 form runninglist
4.2 take task0 as new tcb
4.3 add task2 to blocklist
4.4 use svc ISR swith to task0
4.5 crash
5. use svc ISR swith to task1
Fix:
Move clear spinlock to the end of svc ISR
Signed-off-by: ligd <liguiding1@xiaomi.com>
759 lines
24 KiB
C
759 lines
24 KiB
C
/****************************************************************************
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* sched/irq/irq_csection.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <assert.h>
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#include <nuttx/init.h>
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#include <nuttx/spinlock.h>
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#include <nuttx/sched_note.h>
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#include <arch/irq.h>
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#include "sched/sched.h"
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#include "irq/irq.h"
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#ifdef CONFIG_IRQCOUNT
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/****************************************************************************
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* Public Data
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****************************************************************************/
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#ifdef CONFIG_SMP
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/* This is the spinlock that enforces critical sections when interrupts are
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* disabled.
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*/
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volatile spinlock_t g_cpu_irqlock = SP_UNLOCKED;
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/* Used to keep track of which CPU(s) hold the IRQ lock. */
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volatile spinlock_t g_cpu_irqsetlock;
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volatile cpu_set_t g_cpu_irqset;
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/* Handles nested calls to enter_critical section from interrupt handlers */
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volatile uint8_t g_cpu_nestcount[CONFIG_SMP_NCPUS];
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#endif
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: irq_waitlock
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*
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* Description:
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* Spin to get g_cpu_irqlock, handling a known deadlock condition:
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*
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* A deadlock may occur if enter_critical_section is called from an
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* interrupt handler. Suppose:
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*
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* - CPUn is in a critical section and has the g_cpu_irqlock spinlock.
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* - CPUm takes an interrupt and attempts to enter the critical section.
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* - It spins waiting on g_cpu_irqlock with interrupts disabled.
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* - CPUn calls up_cpu_pause() to pause operation on CPUm. This will
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* issue an inter-CPU interrupt to CPUm
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* - But interrupts are disabled on CPUm so the up_cpu_pause() is never
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* handled, causing the deadlock.
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*
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* This same deadlock can occur in the normal tasking case:
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*
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* - A task on CPUn enters a critical section and has the g_cpu_irqlock
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* spinlock.
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* - Another task on CPUm attempts to enter the critical section but has
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* to wait, spinning to get g_cpu_irqlock with interrupts disabled.
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* - The task on CPUn causes a new task to become ready-to-run and the
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* scheduler selects CPUm. CPUm is requested to pause via a pause
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* interrupt.
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* - But the task on CPUm is also attempting to enter the critical
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* section. Since it is spinning with interrupts disabled, CPUm cannot
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* process the pending pause interrupt, causing the deadlock.
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*
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* This function detects this deadlock condition while spinning with
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* interrupts disabled.
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*
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* Input Parameters:
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* cpu - The index of CPU that is trying to enter the critical section.
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*
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* Returned Value:
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* True: The g_cpu_irqlock spinlock has been taken.
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* False: The g_cpu_irqlock spinlock has not been taken yet, but there is
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* a pending pause interrupt request.
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*
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****************************************************************************/
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#ifdef CONFIG_SMP
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static bool irq_waitlock(int cpu)
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{
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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FAR struct tcb_s *tcb = current_task(cpu);
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/* Notify that we are waiting for a spinlock */
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sched_note_spinlock(tcb, &g_cpu_irqlock);
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#endif
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/* Duplicate the spin_lock() logic from spinlock.c, but adding the check
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* for the deadlock condition.
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*/
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while (spin_trylock_wo_note(&g_cpu_irqlock) == SP_LOCKED)
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{
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/* Is a pause request pending? */
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if (up_cpu_pausereq(cpu))
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{
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/* Yes.. some other CPU is requesting to pause this CPU!
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* Abort the wait and return false.
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*/
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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/* Notify that we have aborted the wait for the spinlock */
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sched_note_spinabort(tcb, &g_cpu_irqlock);
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#endif
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return false;
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}
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}
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/* We have g_cpu_irqlock! */
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#ifdef CONFIG_SCHED_INSTRUMENTATION_SPINLOCKS
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/* Notify that we have the spinlock */
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sched_note_spinlocked(tcb, &g_cpu_irqlock);
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#endif
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return true;
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}
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#endif
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: enter_critical_section
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*
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* Description:
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* Take the CPU IRQ lock and disable interrupts on all CPUs. A thread-
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* specific counter is incremented to indicate that the thread has IRQs
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* disabled and to support nested calls to enter_critical_section().
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*
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****************************************************************************/
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#ifdef CONFIG_SMP
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irqstate_t enter_critical_section(void)
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{
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FAR struct tcb_s *rtcb;
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irqstate_t ret;
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int cpu;
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/* Disable interrupts.
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*
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* NOTE 1: Ideally this should disable interrupts on all CPUs, but most
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* architectures only support disabling interrupts on the local CPU.
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* NOTE 2: Interrupts may already be disabled, but we call up_irq_save()
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* unconditionally because we need to return valid interrupt status in any
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* event.
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* NOTE 3: We disable local interrupts BEFORE taking the spinlock in order
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* to prevent possible waits on the spinlock from interrupt handling on
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* the local CPU.
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*/
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try_again:
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ret = up_irq_save();
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/* Verify that the system has sufficiently initialized so that the task
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* lists are valid.
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*/
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if (g_nx_initstate >= OSINIT_TASKLISTS)
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{
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/* If called from an interrupt handler, then just take the spinlock.
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* If we are already in a critical section, this will lock the CPU
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* in the interrupt handler. Sounds worse than it is.
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*/
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if (up_interrupt_context())
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{
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/* We are in an interrupt handler. How can this happen?
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*
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* 1. We were not in a critical section when the interrupt
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* occurred. In this case, the interrupt was entered with:
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*
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* g_cpu_irqlock = SP_UNLOCKED.
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* g_cpu_nestcount = 0
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* All CPU bits in g_cpu_irqset should be zero
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*
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* 2. We were in a critical section and interrupts on this
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* this CPU were disabled -- this is an impossible case.
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*
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* 3. We were in critical section, but up_irq_save() only
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* disabled local interrupts on a different CPU;
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* Interrupts could still be enabled on this CPU.
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*
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* g_cpu_irqlock = SP_LOCKED.
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* g_cpu_nestcount = 0
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* The bit in g_cpu_irqset for this CPU should be zero
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*
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* 4. An extension of 3 is that we may be re-entered numerous
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* times from the same interrupt handler. In that case:
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*
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* g_cpu_irqlock = SP_LOCKED.
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* g_cpu_nestcount > 0
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* The bit in g_cpu_irqset for this CPU should be zero
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*
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* NOTE: However, the interrupt entry conditions can change due
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* to previous processing by the interrupt handler that may
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* instantiate a new thread that has irqcount > 0 and may then
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* set the bit in g_cpu_irqset and g_cpu_irqlock = SP_LOCKED
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*/
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/* Handle nested calls to enter_critical_section() from the same
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* interrupt.
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*/
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cpu = this_cpu();
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if (g_cpu_nestcount[cpu] > 0)
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{
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DEBUGASSERT(spin_islocked(&g_cpu_irqlock) &&
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g_cpu_nestcount[cpu] < UINT8_MAX);
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g_cpu_nestcount[cpu]++;
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}
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/* This is the first call to enter_critical_section from the
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* interrupt handler.
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*/
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else
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{
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/* Make sure that the g_cpu_irqset was not already set
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* by previous logic on this CPU that was executed by the
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* interrupt handler. We know that the bit in g_cpu_irqset
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* for this CPU was zero on entry into the interrupt handler,
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* so if it is non-zero now then we know that was the case.
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*/
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if ((g_cpu_irqset & (1 << cpu)) == 0)
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{
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/* Wait until we can get the spinlock (meaning that we are
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* no longer blocked by the critical section).
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*/
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try_again_in_irq:
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if (!irq_waitlock(cpu))
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{
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/* We are in a deadlock condition due to a pending
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* pause request interrupt. Break the deadlock by
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* handling the pause request now.
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*/
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DEBUGVERIFY(up_cpu_paused(cpu));
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/* NOTE: As the result of up_cpu_paused(cpu), this CPU
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* might set g_cpu_irqset in nxsched_resume_scheduler()
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* However, another CPU might hold g_cpu_irqlock.
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* To avoid this situation, releae g_cpu_irqlock first.
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*/
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if ((g_cpu_irqset & (1 << cpu)) != 0)
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{
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spin_clrbit(&g_cpu_irqset, cpu, &g_cpu_irqsetlock,
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&g_cpu_irqlock);
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}
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/* NOTE: Here, this CPU does not hold g_cpu_irqlock,
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* so call irq_waitlock(cpu) to acquire g_cpu_irqlock.
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*/
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goto try_again_in_irq;
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}
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}
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/* In any event, the nesting count is now one */
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g_cpu_nestcount[cpu] = 1;
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/* Also set the CPU bit so that other CPUs will be aware that
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* this CPU holds the critical section.
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*/
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spin_setbit(&g_cpu_irqset, cpu, &g_cpu_irqsetlock,
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&g_cpu_irqlock);
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}
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}
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else
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{
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/* Normal tasking environment.
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*
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* Get the TCB of the currently executing task on this CPU (avoid
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* using this_task() which can recurse.
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*/
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cpu = this_cpu();
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rtcb = current_task(cpu);
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DEBUGASSERT(rtcb != NULL);
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/* Do we already have interrupts disabled? */
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if (rtcb->irqcount > 0)
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{
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/* Yes... make sure that the spinlock is set and increment the
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* IRQ lock count.
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*
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* NOTE: If irqcount > 0 then (1) we are in a critical section,
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* and (2) this CPU should hold the lock.
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*/
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DEBUGASSERT(spin_islocked(&g_cpu_irqlock) &&
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(g_cpu_irqset & (1 << this_cpu())) != 0 &&
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rtcb->irqcount < INT16_MAX);
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rtcb->irqcount++;
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}
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else
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{
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/* If we get here with irqcount == 0, then we know that the
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* current task running on this CPU is not in a critical
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* section. However other tasks on other CPUs may be in a
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* critical section. If so, we must wait until they release
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* the spinlock.
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*/
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DEBUGASSERT((g_cpu_irqset & (1 << cpu)) == 0);
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if (!irq_waitlock(cpu))
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{
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/* We are in a deadlock condition due to a pending pause
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* request interrupt. Re-enable interrupts on this CPU
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* and try again. Briefly re-enabling interrupts should
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* be sufficient to permit processing the pending pause
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* request.
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*/
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up_irq_restore(ret);
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goto try_again;
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}
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/* Then set the lock count to 1.
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*
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* Interrupts disables must follow a stacked order. We
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* cannot other context switches to re-order the enabling
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* disabling of interrupts.
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*
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* The scheduler accomplishes this by treating the irqcount
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* like lockcount: Both will disable pre-emption.
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*/
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spin_setbit(&g_cpu_irqset, cpu, &g_cpu_irqsetlock,
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&g_cpu_irqlock);
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rtcb->irqcount = 1;
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/* Note that we have entered the critical section */
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#ifdef CONFIG_SCHED_CRITMONITOR
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nxsched_critmon_csection(rtcb, true);
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#endif
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#ifdef CONFIG_SCHED_INSTRUMENTATION_CSECTION
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sched_note_csection(rtcb, true);
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#endif
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}
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}
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}
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/* Return interrupt status */
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return ret;
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}
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#else
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irqstate_t enter_critical_section(void)
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{
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irqstate_t ret;
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/* Disable interrupts */
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ret = up_irq_save();
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/* Check if we were called from an interrupt handler and that the task
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* lists have been initialized.
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*/
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if (!up_interrupt_context() && g_nx_initstate >= OSINIT_TASKLISTS)
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{
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FAR struct tcb_s *rtcb = this_task();
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DEBUGASSERT(rtcb != NULL);
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/* Have we just entered the critical section? Or is this a nested
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* call to enter_critical_section.
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*/
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DEBUGASSERT(rtcb->irqcount >= 0 && rtcb->irqcount < INT16_MAX);
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if (++rtcb->irqcount == 1)
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{
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/* Note that we have entered the critical section */
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#ifdef CONFIG_SCHED_CRITMONITOR
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nxsched_critmon_csection(rtcb, true);
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#endif
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#ifdef CONFIG_SCHED_INSTRUMENTATION_CSECTION
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sched_note_csection(rtcb, true);
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#endif
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}
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}
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/* Return interrupt status */
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return ret;
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}
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#endif
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/****************************************************************************
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* Name: leave_critical_section
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*
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* Description:
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* Decrement the IRQ lock count and if it decrements to zero then release
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* the spinlock.
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*
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****************************************************************************/
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#ifdef CONFIG_SMP
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void leave_critical_section(irqstate_t flags)
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{
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int cpu;
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/* Verify that the system has sufficiently initialized so that the task
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* lists are valid.
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*/
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if (g_nx_initstate >= OSINIT_TASKLISTS)
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{
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/* If called from an interrupt handler, then just release the
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* spinlock. The interrupt handling logic should already hold the
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* spinlock if enter_critical_section() has been called. Unlocking
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* the spinlock will allow interrupt handlers on other CPUs to execute
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* again.
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*/
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if (up_interrupt_context())
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{
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/* We are in an interrupt handler. Check if the last call to
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* enter_critical_section() was nested.
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*/
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cpu = this_cpu();
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if (g_cpu_nestcount[cpu] > 1)
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{
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/* Yes.. then just decrement the nesting count */
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DEBUGASSERT(spin_islocked(&g_cpu_irqlock));
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g_cpu_nestcount[cpu]--;
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}
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else
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{
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/* No, not nested. Restore the g_cpu_irqset for this CPU
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* and release the spinlock (if necessary).
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*/
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DEBUGASSERT(spin_islocked(&g_cpu_irqlock) &&
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g_cpu_nestcount[cpu] == 1);
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FAR struct tcb_s *rtcb = current_task(cpu);
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DEBUGASSERT(rtcb != NULL);
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if (rtcb->irqcount <= 0)
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{
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spin_clrbit(&g_cpu_irqset, cpu, &g_cpu_irqsetlock,
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&g_cpu_irqlock);
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}
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g_cpu_nestcount[cpu] = 0;
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}
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}
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else
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{
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FAR struct tcb_s *rtcb;
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/* Get the TCB of the currently executing task on this CPU (avoid
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* using this_task() which can recurse.
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*/
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cpu = this_cpu();
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rtcb = current_task(cpu);
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DEBUGASSERT(rtcb != NULL && rtcb->irqcount > 0);
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|
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/* Normal tasking context. We need to coordinate with other
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* tasks.
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*
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* Will we still have interrupts disabled after decrementing the
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* count?
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*/
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if (rtcb->irqcount > 1)
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{
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/* Yes... the spinlock should remain set */
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DEBUGASSERT(spin_islocked(&g_cpu_irqlock));
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rtcb->irqcount--;
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}
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else
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{
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/* No.. Note that we have left the critical section */
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#ifdef CONFIG_SCHED_CRITMONITOR
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nxsched_critmon_csection(rtcb, false);
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#endif
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#ifdef CONFIG_SCHED_INSTRUMENTATION_CSECTION
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sched_note_csection(rtcb, false);
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#endif
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/* Decrement our count on the lock. If all CPUs have
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* released, then unlock the spinlock.
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*/
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DEBUGASSERT(spin_islocked(&g_cpu_irqlock) &&
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(g_cpu_irqset & (1 << cpu)) != 0);
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/* Check if releasing the lock held by this CPU will unlock the
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* critical section.
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*/
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if ((g_cpu_irqset & ~(1 << cpu)) == 0)
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{
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/* Yes.. Check if there are pending tasks and that pre-
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|
* emption is also enabled. This is necessary because we
|
|
* may have deferred the up_release_pending() call in
|
|
* sched_unlock() because we were within a critical
|
|
* section then.
|
|
*/
|
|
|
|
if (g_pendingtasks.head != NULL &&
|
|
!nxsched_islocked_global())
|
|
{
|
|
/* Release any ready-to-run tasks that have collected
|
|
* in g_pendingtasks. NOTE: This operation has a very
|
|
* high likelihood of causing this task to be switched
|
|
* out!
|
|
*/
|
|
|
|
up_release_pending();
|
|
}
|
|
}
|
|
|
|
/* Now, possibly on return from a context switch, clear our
|
|
* count on the lock. If all CPUs have released the lock,
|
|
* then unlock the global IRQ spinlock.
|
|
*/
|
|
|
|
rtcb->irqcount = 0;
|
|
spin_clrbit(&g_cpu_irqset, cpu, &g_cpu_irqsetlock,
|
|
&g_cpu_irqlock);
|
|
|
|
/* Have all CPUs released the lock? */
|
|
}
|
|
}
|
|
}
|
|
|
|
/* 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);
|
|
}
|
|
|
|
#else
|
|
|
|
void leave_critical_section(irqstate_t flags)
|
|
{
|
|
/* Check if we were called from an interrupt handler and that the tasks
|
|
* lists have been initialized.
|
|
*/
|
|
|
|
if (!up_interrupt_context() && g_nx_initstate >= OSINIT_TASKLISTS)
|
|
{
|
|
FAR struct tcb_s *rtcb = this_task();
|
|
DEBUGASSERT(rtcb != NULL);
|
|
|
|
/* Have we left entered the critical section? Or are we still
|
|
* nested.
|
|
*/
|
|
|
|
DEBUGASSERT(rtcb->irqcount > 0);
|
|
if (--rtcb->irqcount <= 0)
|
|
{
|
|
/* Note that we have left the critical section */
|
|
|
|
#ifdef CONFIG_SCHED_CRITMONITOR
|
|
nxsched_critmon_csection(rtcb, false);
|
|
#endif
|
|
#ifdef CONFIG_SCHED_INSTRUMENTATION_CSECTION
|
|
sched_note_csection(rtcb, false);
|
|
#endif
|
|
}
|
|
}
|
|
|
|
/* Restore the previous interrupt state. */
|
|
|
|
up_irq_restore(flags);
|
|
}
|
|
#endif
|
|
|
|
/****************************************************************************
|
|
* Name: irq_cpu_locked
|
|
*
|
|
* Description:
|
|
* Test if the IRQ lock set OR if this CPU holds the IRQ lock
|
|
* There is an interaction with pre-emption controls and IRQ locking:
|
|
* Even if the pre-emption is enabled, tasks will be forced to pend if
|
|
* the IRQ lock is also set UNLESS the CPU starting the task is the
|
|
* holder of the IRQ lock.
|
|
*
|
|
* Input Parameters:
|
|
* cpu - Points to which cpu
|
|
*
|
|
* Returned Value:
|
|
* true - IRQs are locked by a different CPU.
|
|
* false - IRQs are unlocked OR if they are locked BUT this CPU
|
|
* is the holder of the lock.
|
|
*
|
|
* Warning: This values are volatile at only valid at the instance that
|
|
* the CPU set was queried.
|
|
*
|
|
****************************************************************************/
|
|
|
|
#ifdef CONFIG_SMP
|
|
bool irq_cpu_locked(int cpu)
|
|
{
|
|
cpu_set_t irqset;
|
|
|
|
/* g_cpu_irqset is not valid in early phases of initialization */
|
|
|
|
if (g_nx_initstate < OSINIT_OSREADY)
|
|
{
|
|
/* We are still single threaded. In either state of g_cpu_irqlock,
|
|
* the correct return value should always be false.
|
|
*/
|
|
|
|
return false;
|
|
}
|
|
|
|
/* Test if g_cpu_irqlock is locked. We don't really need to use check
|
|
* g_cpu_irqlock to do this, we can use the g_cpu_set.
|
|
*
|
|
* Sample the g_cpu_irqset once. That is an atomic operation. All
|
|
* subsequent operations will operate on the sampled cpu set.
|
|
*/
|
|
|
|
irqset = (cpu_set_t)g_cpu_irqset;
|
|
if (irqset != 0)
|
|
{
|
|
/* Some CPU holds the lock. So g_cpu_irqlock should be locked.
|
|
* Return false if the 'cpu' is the holder of the lock; return
|
|
* true if g_cpu_irqlock is locked, but this CPU is not the
|
|
* holder of the lock.
|
|
*/
|
|
|
|
return ((irqset & (1 << cpu)) == 0);
|
|
}
|
|
|
|
/* No CPU holds the lock */
|
|
|
|
else
|
|
{
|
|
/* In this case g_cpu_irqlock should be unlocked. However, if
|
|
* the lock was established in the interrupt handler AND there are
|
|
* no bits set in g_cpu_irqset, that probably means only that
|
|
* critical section was established from an interrupt handler.
|
|
* Return false in either case.
|
|
*/
|
|
|
|
return false;
|
|
}
|
|
}
|
|
#endif
|
|
|
|
/****************************************************************************
|
|
* Name: restore_critical_section
|
|
*
|
|
* Description:
|
|
* Restore the critical_section
|
|
*
|
|
* Input Parameters:
|
|
* None
|
|
*
|
|
* Returned Value:
|
|
* None
|
|
*
|
|
****************************************************************************/
|
|
|
|
#ifdef CONFIG_SMP
|
|
void restore_critical_section(void)
|
|
{
|
|
/* NOTE: The following logic for adjusting global IRQ controls were
|
|
* derived from nxsched_add_readytorun() and sched_removedreadytorun()
|
|
* Here, we only handles clearing logic to defer unlocking IRQ lock
|
|
* followed by context switching.
|
|
*/
|
|
|
|
FAR struct tcb_s *tcb = this_task();
|
|
int me = this_cpu();
|
|
|
|
/* Adjust global IRQ controls. If irqcount is greater than zero,
|
|
* then this task/this CPU holds the IRQ lock
|
|
*/
|
|
|
|
if (tcb->irqcount > 0)
|
|
{
|
|
/* Do notihing here
|
|
* NOTE: spin_setbit() is done in nxsched_add_readytorun()
|
|
* and nxsched_remove_readytorun()
|
|
*/
|
|
}
|
|
|
|
/* No.. This CPU will be relinquishing the lock. But this works
|
|
* differently if we are performing a context switch from an
|
|
* interrupt handler and the interrupt handler has established
|
|
* a critical section. We can detect this case when
|
|
* g_cpu_nestcount[me] > 0.
|
|
*/
|
|
|
|
else if (g_cpu_nestcount[me] <= 0)
|
|
{
|
|
/* Release our hold on the IRQ lock. */
|
|
|
|
if ((g_cpu_irqset & (1 << me)) != 0)
|
|
{
|
|
spin_clrbit(&g_cpu_irqset, me, &g_cpu_irqsetlock,
|
|
&g_cpu_irqlock);
|
|
}
|
|
}
|
|
}
|
|
#endif /* CONFIG_SMP */
|
|
|
|
#endif /* CONFIG_IRQCOUNT */
|