349 lines
11 KiB
C
349 lines
11 KiB
C
/****************************************************************************
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* sched/sched/sched_unlock.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 <assert.h>
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#include <nuttx/irq.h>
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#include <nuttx/clock.h>
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#include <nuttx/arch.h>
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#include <nuttx/sched_note.h>
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#include "irq/irq.h"
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#include "sched/sched.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: sched_unlock
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*
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* Description:
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* This function decrements the preemption lock count. Typically this
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* is paired with sched_lock() and concludes a critical section of
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* code. Preemption will not be unlocked until sched_unlock() has
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* been called as many times as sched_lock(). When the lockcount is
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* decremented to zero, any tasks that were eligible to preempt the
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* current task will execute.
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*
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****************************************************************************/
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#ifdef CONFIG_SMP
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int sched_unlock(void)
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{
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FAR struct tcb_s *rtcb;
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/* This operation is safe because the scheduler is locked and no context
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* switch may occur.
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*/
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rtcb = this_task();
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/* Check for some special cases: (1) rtcb may be NULL only during
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* early boot-up phases, and (2) sched_unlock() should have no
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* effect if called from the interrupt level.
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*/
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if (rtcb != NULL && !up_interrupt_context())
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{
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/* Prevent context switches throughout the following. */
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irqstate_t flags = enter_critical_section();
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int cpu = this_cpu();
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/* Decrement the preemption lock counter */
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if (rtcb->lockcount > 0)
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{
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rtcb->lockcount--;
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}
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/* Check if the lock counter has decremented to zero. If so,
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* then pre-emption has been re-enabled.
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*/
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if (rtcb->lockcount <= 0)
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{
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/* Note that we no longer have pre-emption disabled. */
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#ifdef CONFIG_SCHED_CRITMONITOR
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nxsched_critmon_preemption(rtcb, false);
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#endif
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#ifdef CONFIG_SCHED_INSTRUMENTATION_PREEMPTION
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sched_note_premption(rtcb, false);
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#endif
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/* Set the lock count to zero */
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rtcb->lockcount = 0;
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/* The lockcount has decremented to zero and we need to perform
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* release our hold on the lock.
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*/
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DEBUGASSERT(g_cpu_schedlock == SP_LOCKED &&
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(g_cpu_lockset & (1 << cpu)) != 0);
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spin_clrbit(&g_cpu_lockset, cpu, &g_cpu_locksetlock,
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&g_cpu_schedlock);
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/* Release any ready-to-run tasks that have collected in
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* g_pendingtasks.
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*
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* NOTE: This operation has a very high likelihood of causing
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* this task to be switched out!
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*/
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/* In the SMP case, the tasks remains pend(1) if we are
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* in a critical section, i.e., g_cpu_irqlock is locked by other
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* CPUs, or (2) other CPUs still have pre-emption disabled, i.e.,
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* g_cpu_schedlock is locked. In those cases, the release of the
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* pending tasks must be deferred until those conditions are met.
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*
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* There are certain conditions that we must avoid by preventing
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* releasing the pending tasks while within the critical section
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* of other CPUs. This logic does that and there is matching
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* logic in nxsched_add_readytorun to avoid starting new tasks
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* within the critical section (unless the CPU is the holder of
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* the lock).
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*
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* REVISIT: If this CPU is only one that holds the IRQ lock, then
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* we should go ahead and release the pending tasks. See the logic
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* leave_critical_section(): It will call up_release_pending()
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* BEFORE it clears IRQ lock.
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*/
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if (!nxsched_islocked_global() && !irq_cpu_locked(cpu) &&
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g_pendingtasks.head != NULL)
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{
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up_release_pending();
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}
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#if CONFIG_RR_INTERVAL > 0
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/* If (1) the task that was running supported round-robin
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* scheduling and (2) if its time slice has already expired, but
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* (3) it could not slice out because pre-emption was disabled,
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* then we need to swap the task out now and reassess the interval
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* timer for the next time slice.
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*/
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if ((rtcb->flags & TCB_FLAG_POLICY_MASK) == TCB_FLAG_SCHED_RR &&
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rtcb->timeslice == 0)
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{
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/* Yes.. that is the situation. But one more thing. The call
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* to up_release_pending() above may have actually replaced
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* the task at the head of the ready-to-run list. In that
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* case, we need only to reset the timeslice value back to the
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* maximum.
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*/
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if (rtcb != current_task(cpu))
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{
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rtcb->timeslice = MSEC2TICK(CONFIG_RR_INTERVAL);
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}
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#ifdef CONFIG_SCHED_TICKLESS
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else
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{
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nxsched_reassess_timer();
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}
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#endif
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}
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#endif
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#ifdef CONFIG_SCHED_SPORADIC
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#if CONFIG_RR_INTERVAL > 0
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else
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#endif
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/* If (1) the task that was running supported sporadic scheduling
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* and (2) if its budget slice has already expired, but (3) it
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* could not slice out because pre-emption was disabled, then we
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* need to swap the task out now and reassess the interval timer
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* for the next time slice.
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*/
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if ((rtcb->flags & TCB_FLAG_POLICY_MASK) == TCB_FLAG_SCHED_SPORADIC
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&& rtcb->timeslice < 0)
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{
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/* Yes.. that is the situation. Force the low-priority state
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* now
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*/
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nxsched_sporadic_lowpriority(rtcb);
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#ifdef CONFIG_SCHED_TICKLESS
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/* Make sure that the call to up_release_pending() did not
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* change the currently active task.
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*/
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if (rtcb == current_task(cpu))
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{
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nxsched_reassess_timer();
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}
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#endif
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}
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#endif
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}
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leave_critical_section(flags);
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}
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return OK;
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}
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#else /* CONFIG_SMP */
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int sched_unlock(void)
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{
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FAR struct tcb_s *rtcb = this_task();
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/* Check for some special cases: (1) rtcb may be NULL only during
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* early boot-up phases, and (2) sched_unlock() should have no
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* effect if called from the interrupt level.
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*/
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if (rtcb != NULL && !up_interrupt_context())
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{
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/* Prevent context switches throughout the following. */
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irqstate_t flags = enter_critical_section();
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/* Decrement the preemption lock counter */
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if (rtcb->lockcount > 0)
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{
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rtcb->lockcount--;
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}
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/* Check if the lock counter has decremented to zero. If so,
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* then pre-emption has been re-enabled.
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*/
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if (rtcb->lockcount <= 0)
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{
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/* Note that we no longer have pre-emption disabled. */
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#ifdef CONFIG_SCHED_CRITMONITOR
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nxsched_critmon_preemption(rtcb, false);
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#endif
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#ifdef CONFIG_SCHED_INSTRUMENTATION_PREEMPTION
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sched_note_premption(rtcb, false);
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#endif
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/* Set the lock count to zero */
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rtcb->lockcount = 0;
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/* Release any ready-to-run tasks that have collected in
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* g_pendingtasks.
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*
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* NOTE: This operation has a very high likelihood of causing
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* this task to be switched out!
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*
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* In the single CPU case, decrementing irqcount to zero is
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* sufficient to release the pending tasks. Further, in that
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* configuration, critical sections and pre-emption can operate
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* fully independently.
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*/
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if (g_pendingtasks.head != NULL)
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{
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up_release_pending();
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}
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#if CONFIG_RR_INTERVAL > 0
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/* If (1) the task that was running supported round-robin
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* scheduling and (2) if its time slice has already expired, but
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* (3) it could not slice out because pre-emption was disabled,
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* then we need to swap the task out now and reassess the interval
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* timer for the next time slice.
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*/
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if ((rtcb->flags & TCB_FLAG_POLICY_MASK) == TCB_FLAG_SCHED_RR &&
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rtcb->timeslice == 0)
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{
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/* Yes.. that is the situation. But one more thing. The call
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* to up_release_pending() above may have actually replaced
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* the task at the head of the ready-to-run list. In that
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* case, we need only to reset the timeslice value back to the
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* maximum.
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*/
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if (rtcb != this_task())
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{
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rtcb->timeslice = MSEC2TICK(CONFIG_RR_INTERVAL);
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}
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#ifdef CONFIG_SCHED_TICKLESS
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else
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{
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nxsched_reassess_timer();
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}
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#endif
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}
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#endif
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#ifdef CONFIG_SCHED_SPORADIC
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#if CONFIG_RR_INTERVAL > 0
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else
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#endif
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/* If (1) the task that was running supported sporadic scheduling
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* and (2) if its budget slice has already expired, but (3) it
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* could not slice out because pre-emption was disabled, then we
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* need to swap the task out now and reassess the interval timer
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* for the next time slice.
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*/
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if ((rtcb->flags & TCB_FLAG_POLICY_MASK) == TCB_FLAG_SCHED_SPORADIC
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&& rtcb->timeslice < 0)
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{
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/* Yes.. that is the situation. Force the low-priority state
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* now
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*/
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nxsched_sporadic_lowpriority(rtcb);
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#ifdef CONFIG_SCHED_TICKLESS
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/* Make sure that the call to up_release_pending() did not
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* change the currently active task.
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*/
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if (rtcb == this_task())
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{
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nxsched_reassess_timer();
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}
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#endif
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}
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#endif
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}
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leave_critical_section(flags);
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}
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return OK;
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}
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#endif /* CONFIG_SMP */
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