nuttx/arch/xtensa/src/common/xtensa_cpupause.c

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/****************************************************************************
* arch/xtensa/src/common/xtensa_cpupause.c
*
* Copyright (C) 2016 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 <nuttx/config.h>
#include <stdint.h>
#include <nuttx/arch.h>
#include <nuttx/sched.h>
#include <nuttx/spinlock.h>
#include <nuttx/sched_note.h>
#include "xtensa.h"
#include "sched/sched.h"
#ifdef CONFIG_SMP
/****************************************************************************
* Private Data
****************************************************************************/
static spinlock_t g_cpu_wait[CONFIG_SMP_NCPUS] SP_SECTION;
static spinlock_t g_cpu_paused[CONFIG_SMP_NCPUS] SP_SECTION;
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: up_cpu_pausereq
*
* Description:
* Return true if a pause request is pending for this CPU.
*
* Input Parameters:
* cpu - The index of the CPU to be queried
*
* Returned Value:
* true = a pause request is pending.
* false = no pasue request is pending.
*
****************************************************************************/
bool up_cpu_pausereq(int cpu)
{
return spin_islocked(&g_cpu_paused[cpu]);
}
/****************************************************************************
* Name: up_cpu_paused
*
* Description:
* Handle a pause request from another CPU. Normally, this logic is
* executed from interrupt handling logic within the architecture-specific
* However, it is sometimes necessary necessary to perform the pending
* pause operation in other contexts where the interrupt cannot be taken
* in order to avoid deadlocks.
*
* This function performs the following operations:
*
* 1. It saves the current task state at the head of the current assigned
* task list.
* 2. It waits on a spinlock, then
* 3. Returns from interrupt, restoring the state of the new task at the
* head of the ready to run list.
*
* Input Parameters:
* cpu - The index of the CPU to be paused
*
* Returned Value:
* On success, OK is returned. Otherwise, a negated errno value indicating
* the nature of the failure is returned.
*
****************************************************************************/
int up_cpu_paused(int cpu)
{
FAR struct tcb_s *otcb = this_task();
FAR struct tcb_s *ntcb;
/* Update scheduler parameters */
sched_suspend_scheduler(otcb);
#ifdef CONFIG_SCHED_INSTRUMENTATION
/* Notify that we are paused */
sched_note_cpu_paused(otcb);
#endif
/* Copy the CURRENT_REGS into the OLD TCB (otcb). The co-processor state
* will be saved as part of the return from xtensa_irq_dispatch().
*/
xtensa_savestate(otcb->xcp.regs);
/* Wait for the spinlock to be released */
spin_unlock(&g_cpu_paused[cpu]);
spin_lock(&g_cpu_wait[cpu]);
/* Upon return, we will restore the exception context of the new TCB
* (ntcb) at the head of the ready-to-run task list.
*/
ntcb = this_task();
#ifdef CONFIG_SCHED_INSTRUMENTATION
/* Notify that we have resumed */
sched_note_cpu_resumed(ntcb);
#endif
/* Reset scheduler parameters */
sched_resume_scheduler(ntcb);
/* Did the task at the head of the list change? */
if (otcb != ntcb)
{
/* Set CURRENT_REGS to the context save are of the new TCB to start.
* This will inform the return-from-interrupt logic that a context
* switch must be performed.
*/
xtensa_restorestate(ntcb->xcp.regs);
}
spin_unlock(&g_cpu_wait[cpu]);
}
/****************************************************************************
* Name: xtensa_pause_handler
*
* Description:
* This is the handler for CPU_INTCODE_PAUSE CPU interrupt. This
* implements up_cpu_pause() by performing the following operations:
*
* 1. The current task state at the head of the current assigned task
* list was saved when the interrupt was entered.
* 2. This function simply waits on a spinlock, then returns.
* 3. Upon return, the interrupt exit logic will restore the state of
* the new task at the head of the ready to run list.
*
* Input Parameters:
* None
*
* Returned Value:
* None
*
****************************************************************************/
void xtensa_pause_handler(void)
{
(void)up_cpu_paused(up_cpu_index());
}
/****************************************************************************
* Name: up_cpu_pause
*
* Description:
* Save the state of the current task at the head of the
* g_assignedtasks[cpu] task list and then pause task execution on the
* CPU.
*
* This function is called by the OS when the logic executing on one CPU
* needs to modify the state of the g_assignedtasks[cpu] list for another
* CPU.
*
* Input Parameters:
* cpu - The index of the CPU to be stopped.
*
* Returned Value:
* Zero on success; a negated errno value on failure.
*
****************************************************************************/
int up_cpu_pause(int cpu)
{
int ret;
#ifdef CONFIG_SCHED_INSTRUMENTATION
/* Notify of the pause event */
sched_note_cpu_pause(this_task(), cpu);
#endif
DEBUGASSERT(cpu >= 0 && cpu < CONFIG_SMP_NCPUS && cpu != this_cpu());
/* Take the both spinlocks. The g_cpu_wait spinlock will prevent the SGI2
* handler from returning until up_cpu_resume() is called; g_cpu_paused
* is a handshake that will prefent this function from returning until
* the CPU is actually paused.
*/
DEBUGASSERT(!spin_islocked(&g_cpu_wait[cpu]) &&
!spin_islocked(&g_cpu_paused[cpu]));
spin_lock(&g_cpu_wait[cpu]);
spin_lock(&g_cpu_paused[cpu]);
/* Execute SGI2 */
2016-10-31 15:29:28 +01:00
ret = xtensa_intercpu_interrupt(cpu, CPU_INTCODE_PAUSE);
if (ret < 0)
{
/* What happened? Unlock the g_cpu_wait spinlock */
spin_unlock(&g_cpu_wait[cpu]);
}
else
{
/* Wait for the other CPU to unlock g_cpu_paused meaning that
* it is fully paused and ready for up_cpu_resume();
*/
spin_lock(&g_cpu_paused[cpu]);
}
spin_unlock(&g_cpu_paused[cpu]);
/* On successful return g_cpu_wait will be locked, the other CPU will be
* spinninf on g_cpu_wait and will not continue until g_cpu_resume() is
* called. g_cpu_paused will be unlocked in any case.
*/
return ret;
}
/****************************************************************************
* Name: up_cpu_resume
*
* Description:
* Restart the cpu after it was paused via up_cpu_pause(), restoring the
* state of the task at the head of the g_assignedtasks[cpu] list, and
* resume normal tasking.
*
* This function is called after up_cpu_pause in order resume operation of
* the CPU after modifying its g_assignedtasks[cpu] list.
*
* Input Parameters:
* cpu - The index of the CPU being re-started.
*
* Returned Value:
* Zero on success; a negated errno value on failure.
*
****************************************************************************/
int up_cpu_resume(int cpu)
{
#ifdef CONFIG_SCHED_INSTRUMENTATION
/* Notify of the resume event */
sched_note_cpu_resume(this_task(), cpu);
#endif
DEBUGASSERT(cpu >= 0 && cpu < CONFIG_SMP_NCPUS && cpu != this_cpu());
/* Release the spinlock. Releasing the spinlock will cause the SGI2
* handler on 'cpu' to continue and return from interrupt to the newly
* established thread.
*/
DEBUGASSERT(spin_islocked(&g_cpu_wait[cpu]) &&
!spin_islocked(&g_cpu_paused[cpu]));
spin_unlock(&g_cpu_wait[cpu]);
return OK;
}
#endif /* CONFIG_SMP */