/****************************************************************************
 * arch/ceva/src/common/ceva_schedulesigaction.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <string.h>
#include <debug.h>

#include <nuttx/irq.h>
#include <nuttx/arch.h>

#include "sched/sched.h"
#include "ceva_internal.h"

#ifndef CONFIG_DISABLE_SIGNALS

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: up_schedule_sigaction
 *
 * Description:
 *   This function is called by the OS when one or more
 *   signal handling actions have been queued for execution.
 *   The architecture specific code must configure things so
 *   that the 'sigdeliver' callback is executed on the thread
 *   specified by 'tcb' as soon as possible.
 *
 *   This function may be called from interrupt handling logic.
 *
 *   This operation should not cause the task to be unblocked
 *   nor should it cause any immediate execution of sigdeliver.
 *   Typically, a few cases need to be considered:
 *
 *   (1) This function may be called from an interrupt handler
 *       During interrupt processing, all xcptcontext structures
 *       should be valid for all tasks.  That structure should
 *       be modified to invoke sigdeliver() either on return
 *       from (this) interrupt or on some subsequent context
 *       switch to the recipient task.
 *   (2) If not in an interrupt handler and the tcb is NOT
 *       the currently executing task, then again just modify
 *       the saved xcptcontext structure for the recipient
 *       task so it will invoke sigdeliver when that task is
 *       later resumed.
 *   (3) If not in an interrupt handler and the tcb IS the
 *       currently executing task -- just call the signal
 *       handler now.
 *
 ****************************************************************************/

void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
{
  sinfo("tcb=%p sigdeliver=%p\n", tcb, sigdeliver);
  DEBUGASSERT(tcb != NULL && sigdeliver != NULL);

  /* Refuse to handle nested signal actions */

  if (tcb->xcp.sigdeliver == NULL)
    {
      /* First, handle some special cases when the signal is being delivered
       * to task that is currently executing on any CPU.
       */

      sinfo("rtcb=%p CURRENT_REGS=%p\n", this_task(), CURRENT_REGS);

      if (tcb->task_state == TSTATE_TASK_RUNNING)
        {
          uint8_t me  = this_cpu();
#ifdef CONFIG_SMP
          uint8_t cpu = tcb->cpu;
#else
          uint8_t cpu = 0;
#endif

          /* CASE 1:  We are not in an interrupt handler and a task is
           * signaling itself for some reason.
           */

          if (cpu == me && !CURRENT_REGS)
            {
              /* In this case just deliver the signal now. */

              sigdeliver(tcb);
            }

          /* CASE 2:  The task that needs to receive the signal is running.
           * This could happen if the task is running on another CPU OR if
           * we are in an interrupt handler and the task is running on this
           * CPU.  In the former case, we will have to PAUSE the other CPU
           * first.  But in either case, we will have to modify the return
           * state as well as the state in the TCB.
           */

          else
            {
#ifdef CONFIG_SMP
              /* If we signaling a task running on the other CPU, we have
               * to PAUSE the other CPU.
               */

              if (cpu != me)
                {
                  /* Pause the CPU */

                  up_cpu_pause(cpu);

                  /* Wait while the pause request is pending */

                  while (up_cpu_pausereq(cpu))
                    {
                    }
                }

              /* Now tcb on the other CPU can be accessed safely */
#endif

              /* Save the current register context location */

              tcb->xcp.saved_regs = g_current_regs[cpu];
              tcb->xcp.sigdeliver = (void *)sigdeliver;

              /* Duplicate the register context.  These will be
               * restored by the signal trampoline after the signal has been
               * delivered.
               */

              g_current_regs[cpu] -= XCPTCONTEXT_REGS;
              memcpy(g_current_regs[cpu], g_current_regs[cpu]
                    + XCPTCONTEXT_REGS, XCPTCONTEXT_SIZE);

              g_current_regs[cpu][REG_SP]  = (uint32_t)g_current_regs[cpu];

              /* Then set up to vector to the trampoline with interrupts
               * unchanged.  We must already be in privileged thread mode
               * to be here.
               */

              g_current_regs[cpu][REG_PC]  = (uint32_t)ceva_sigdeliver;
#ifdef REG_OM
              g_current_regs[cpu][REG_OM] &= ~REG_OM_MASK;
              g_current_regs[cpu][REG_OM] |=  REG_OM_KERNEL;
#endif

#ifdef CONFIG_SMP
              /* RESUME the other CPU if it was PAUSED */

              if (cpu != me)
                {
                  up_cpu_resume(cpu);
                }
#endif
            }
        }

      /* Otherwise, we are (1) signaling a task is not running from an
       * interrupt handler or (2) we are not in an interrupt handler and the
       * running task is signaling some other non-running task.
       */

      else
        {
          /* Save the current register context location */

          tcb->xcp.saved_regs = tcb->xcp.regs;
          tcb->xcp.sigdeliver = (void *)sigdeliver;

          /* Duplicate the register context.  These will be restored
           * by the signal trampoline after the signal has been delivered.
           */

          tcb->xcp.regs -= XCPTCONTEXT_REGS;
          memcpy(tcb->xcp.regs, tcb->xcp.regs
                + XCPTCONTEXT_REGS, XCPTCONTEXT_SIZE);

          tcb->xcp.regs[REG_SP]  = (uint32_t)tcb->xcp.regs;

          /* Then set up to vector to the trampoline with interrupts
           * unchanged.  We must already be in privileged thread mode to be
           * here.
           */

          tcb->xcp.regs[REG_PC]  = (uint32_t)ceva_sigdeliver;
#ifdef REG_OM
          tcb->xcp.regs[REG_OM] &= ~REG_OM_MASK;
          tcb->xcp.regs[REG_OM] |=  REG_OM_KERNEL;
#endif
        }
    }
}

#endif /* !CONFIG_DISABLE_SIGNALS */
