Boot Linux faster!

Check our new training course

Boot Linux faster!

Check our new training course
and Creative Commons CC-BY-SA
lecture and lab materials

Bootlin logo

Elixir Cross Referencer

 * Copyright (c) 2013-2014 Wind River Systems, Inc.
 * Licensed 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
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.

 * @file
 * @brief ARM CORTEX-M3 exception/interrupt exit API
 * Provides functions for performing kernel handling when exiting exceptions or
 * interrupts that are installed directly in the vector table (i.e. that are not
 * wrapped around by _isr_wrapper()).


#include <nano_private.h>
#include <offsets.h>
#include <toolchain.h>
#include <arch/cpu.h>



  #define _EXIT_EXC_IF_FIBER_PREEMPTED beq _ExcExitWithGdbStub
                                     it eq
                                     bxeq lr

 * @brief Kernel housekeeping when exiting interrupt handler installed
 *            directly in vector table
 * Kernel allows installing interrupt handlers (ISRs) directly into the vector
 * table to get the lowest interrupt latency possible. This allows the ISR to be
 * invoked directly without going through a software interrupt table. However,
 * upon exiting the ISR, some kernel work must still be performed, namely
 * possible context switching. While ISRs connected in the software interrupt
 * table do this automatically via a wrapper, ISRs connected directly in the
 * vector table must invoke _IntExit() as the *very last* action before
 * returning.
 * e.g.
 * void myISR(void)
 *     {
 *     printk("in %s\n", __FUNCTION__);
 *     doStuff();
 *     _IntExit();
 *     }
 * @return N/A

SECTION_SUBSEC_FUNC(TEXT, _HandlerModeExit, _IntExit)

/* _IntExit falls through to _ExcExit (they are aliases of each other) */

 * @brief Kernel housekeeping when exiting exception handler installed
 *            directly in vector table
 * See _IntExit().
 * @return N/A

SECTION_SUBSEC_FUNC(TEXT, _HandlerModeExit, _ExcExit)

    ldr r1, =_nanokernel

    /* is the current thread preemptible (task) ? */
    ldr r2, [r1, #__tNANO_flags_OFFSET]
    ands.w r2, #PREEMPTIBLE

    /* is there a fiber ready ? */
    ldr r2, [r1, #__tNANO_fiber_OFFSET]
    cmp r2, #0

    /* context switch required, pend the PendSV exception */
    ldr r1, =_SCS_ICSR
    ldr r2, =_SCS_ICSR_PENDSV
    str r2, [r1]



    bx lr