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//==========================================================================

//

//      src/ecos/synch.c

//

//==========================================================================

//####BSDCOPYRIGHTBEGIN####

//

// -------------------------------------------

//

// Portions of this software may have been derived from OpenBSD, 

// FreeBSD or other sources, and are covered by the appropriate

// copyright disclaimers included herein.

//

// Portions created by Red Hat are

// Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.

//

// -------------------------------------------

//

//####BSDCOPYRIGHTEND####

//==========================================================================

//==========================================================================

//

//      ecos/synch.c

//

//      eCos wrapper and synch functions

//

//==========================================================================

//####BSDCOPYRIGHTBEGIN####

//

// -------------------------------------------

//

// Portions of this software may have been derived from OpenBSD or other sources,

// and are covered by the appropriate copyright disclaimers included herein.

//

// -------------------------------------------

//

//####BSDCOPYRIGHTEND####

//==========================================================================

//#####DESCRIPTIONBEGIN####

//

// Author(s):    gthomas, hmt

// Contributors: gthomas, hmt

// Date:         2000-01-10

// Purpose:      

// Description:  

//              

//

//####DESCRIPTIONEND####

//

//==========================================================================

// Synch routines, etc., used by network code

#include <sys/param.h>

#include <pkgconf/net.h>

#include <cyg/infra/diag.h>

#include <cyg/hal/hal_intr.h>

#include <cyg/kernel/kapi.h>

#include <cyg/infra/cyg_ass.h>

//---------------------------- splx() emulation ------------------------------

// This contains both the SPLX stuff and tsleep/wakeup - because those must

// be SPLX aware.  They release the SPLX lock when sleeping, and reclaim it

// (if needs be) at wakeup.

//

// The variable spl_state (and the associated bit patterns) is used to keep

// track of the "splx()" level.  This is an artifact of the original stack,

// based on the BSD interrupt world (interrupts and processing could be

// masked based on a level value, supported by hardware).  This is not very

// real-time, so the emulation uses proper eCos tools and techniques to

// accomplish the same result.  The key here is in the analysis of the

// various "levels", why they are used, etc.

//

// SPL_IMP is called in order to protect internal data structures

// short-term, primarily so that interrupt processing does not interfere

// with them.

// 

// SPL_CLOCK is called in order to ensure that a timestamp is valid i.e. no

// time passes while the stamp is being taken (since it is a potentially

// non-idempotent data structure).

//

// SPL_SOFTNET is used to prevent all other stack processing, including

// interrupts (DSRs), etc.

//

// SPL_INTERNAL is used when running the pseudo-DSR in timeout.c - this

// runs what should really be the network interface device's DSR, and any

// timeout routines that are scheduled.  (They are broken out into a thread

// to isolate the network locking from the rest of the system)

//

// NB a thread in thi state can tsleep(); see below.  Tsleep releases and

// reclaims the locks and so on.  This necessary because of the possible

// conflict where

//     I splsoft

//     I tsleep

//     He runs, he is lower priority

//     He splsofts

//     He or something else awakens me

//     I want to run, but he has splsoft, so I wait

//     He runs and releases splsoft

//     I awaken and go.

static volatile cyg_uint32 spl_state = 0;

#define SPL_IMP      0x01

#define SPL_NET      0x02

#define SPL_CLOCK    0x04

#define SPL_SOFTNET  0x08

#define SPL_INTERNAL 0x10

static cyg_mutex_t splx_mutex;

static volatile cyg_handle_t splx_thread;

#ifdef CYGIMPL_TRACE_SPLX   

#define SPLXARGS const char *file, const int line

#define SPLXMOREARGS , const char *file, const int line

#define SPLXTRACE do_sched_event(__FUNCTION__, file, line, spl_state)

#else

#define SPLXARGS void

#define SPLXMOREARGS

#define SPLXTRACE

#endif

static inline cyg_uint32

spl_any( cyg_uint32 which )

{

    cyg_uint32 old_spl = spl_state;

    if ( cyg_thread_self() != splx_thread ) {

        cyg_mutex_lock( &splx_mutex );

        old_spl = 0; // Free when we unlock this context

        CYG_ASSERT( 0 == splx_thread, "Thread still owned" );

        CYG_ASSERT( 0 == spl_state, "spl still set" );

        splx_thread = cyg_thread_self();

    }

    CYG_ASSERT( splx_mutex.locked, "spl_any: mutex not locked" );

    CYG_ASSERT( (cyg_handle_t)splx_mutex.owner == cyg_thread_self(),

                "spl_any: mutex not mine" );

    spl_state |= which;

    return old_spl;

}

cyg_uint32

cyg_splimp(SPLXARGS)

{

    SPLXTRACE;

    return spl_any( SPL_IMP );

}

cyg_uint32

cyg_splclock(SPLXARGS)

{

    SPLXTRACE;

    return spl_any( SPL_CLOCK );

}

cyg_uint32

cyg_splnet(SPLXARGS)

{

    SPLXTRACE;

    return spl_any( SPL_NET );

}

cyg_uint32

cyg_splhigh(SPLXARGS)

{

    SPLXTRACE;

    // splhigh did SPLSOFTNET in the contrib, so this is the same

    return spl_any( SPL_SOFTNET );

}

cyg_uint32

cyg_splsoftnet(SPLXARGS)

{

    SPLXTRACE;

    return spl_any( SPL_SOFTNET );

}

cyg_uint32

cyg_splinternal(SPLXARGS)

{

    SPLXTRACE;

    return spl_any( SPL_INTERNAL );

}

//

// Return to a previous interrupt state/level.

//

void

cyg_splx(cyg_uint32 old_state SPLXMOREARGS)

{

    SPLXTRACE;

    CYG_ASSERT( 0 != spl_state, "No state set" );

    CYG_ASSERT( splx_mutex.locked, "splx: mutex not locked" );

    CYG_ASSERT( (cyg_handle_t)splx_mutex.owner == cyg_thread_self(),

                "splx: mutex not mine" );

    spl_state &= old_state;

    if ( 0 == spl_state ) {

        splx_thread = 0;

        cyg_mutex_unlock( &splx_mutex );

    }

}

//------------------ tsleep() and wakeup() emulation ---------------------------

//

// Structure used to keep track of 'tsleep' style events

//

struct wakeup_event {

    void *chan;

    cyg_sem_t sem;

};

static struct wakeup_event wakeup_list[CYGPKG_NET_NUM_WAKEUP_EVENTS];

// Called to initialize structures used by timeout functions

void

cyg_tsleep_init(void)

{

    int i;

    struct wakeup_event *ev;

    // Create list of "wakeup event" semaphores

    for (i = 0, ev = wakeup_list;  i < CYGPKG_NET_NUM_WAKEUP_EVENTS;  i++, ev++) {

        ev->chan = 0;

        cyg_semaphore_init(&ev->sem, 0);

    }

    // Initialize the mutex and thread id:

    cyg_mutex_init( &splx_mutex );

    splx_thread = 0;

}

//

// Signal an event

void

cyg_wakeup(void *chan)

{

    int i;

    struct wakeup_event *ev;

    cyg_scheduler_lock(); // Ensure scan is safe

    // NB this is broadcast semantics because a sleeper/wakee holds the

    // slot until they exit.  This avoids a race condition whereby the

    // semaphore can get an extra post - and then the slot is freed, so the

    // sem wait returns immediately, AOK, so the slot wasn't freed.

    for (i = 0, ev = wakeup_list;  i < CYGPKG_NET_NUM_WAKEUP_EVENTS;  i++, ev++)

        if (ev->chan == chan)

            cyg_semaphore_post(&ev->sem);

    cyg_scheduler_unlock();

}

// ------------------------------------------------------------------------

// Wait for an event with timeout

//   tsleep(event, priority, state, timeout)

//     event - the thing to wait for

//     priority - unused

//     state    - a descriptive message

//     timeout  - max time (in ticks) to wait

//   returns:

//     0         - event was "signalled"

//     ETIMEDOUT - timeout occurred

//     EINTR     - thread broken out of sleep

//

int

cyg_tsleep(void *chan, int pri, char *wmesg, int timo)

{

    int i, res = 0;

    struct wakeup_event *ev;

    cyg_tick_count_t sleep_time;

    cyg_handle_t self = cyg_thread_self();

    int old_splflags = 0; // no flags held

    cyg_scheduler_lock();

    // Safely find a free slot:

    for (i = 0, ev = wakeup_list;  i < CYGPKG_NET_NUM_WAKEUP_EVENTS;  i++, ev++) {

        if (ev->chan == 0) {

            ev->chan = chan;

            break;

        }

    }

    CYG_ASSERT( i <  CYGPKG_NET_NUM_WAKEUP_EVENTS, "no sleep slots" );

    CYG_ASSERT( 1 == cyg_scheduler_read_lock(),

                "Tsleep - called with scheduler locked" );

    // Defensive:

    if ( i >= CYGPKG_NET_NUM_WAKEUP_EVENTS ) {

        cyg_scheduler_unlock();

        return ETIMEDOUT;

    }

    // If we are the owner, then we must release the mutex when

    // we wait.

    if ( self == splx_thread ) {

        old_splflags = spl_state; // Keep them for restoration

        CYG_ASSERT( spl_state, "spl_state not set" );

        // Also want to assert that the mutex is locked...

        CYG_ASSERT( splx_mutex.locked, "Splx mutex not locked" );

        CYG_ASSERT( (cyg_handle_t)splx_mutex.owner == self, "Splx mutex not mine" );

        splx_thread = 0;

        spl_state = 0;

        cyg_mutex_unlock( &splx_mutex );

    }

    // Re-initialize the semaphore - it might have counted up arbitrarily

    // in the time between a prior sleeper being signalled and them

    // actually running.

    cyg_semaphore_init(&ev->sem, 0);

    // This part actually does the wait:

    // As of the new kernel, we can do this without unlocking the scheduler

    if (timo) {

        sleep_time = cyg_current_time() + timo;

        if (!cyg_semaphore_timed_wait(&ev->sem, sleep_time)) {

            if( cyg_current_time() >= sleep_time )

                res = ETIMEDOUT;

            else

                res = EINTR;

        }

    } else {

        if (!cyg_semaphore_wait(&ev->sem) ) {

            res = EINTR;

        }

    }

    ev->chan = 0;  // Free the slot - the wakeup call cannot do this.

    if ( old_splflags ) { // restore to previous state

        // As of the new kernel, we can do this with the scheduler locked

        cyg_mutex_lock( &splx_mutex ); // this might wait

        CYG_ASSERT( 0 == splx_thread, "Splx thread set in tsleep" );

        CYG_ASSERT( 0 == spl_state, "spl_state set in tsleep" );

        splx_thread = self; // got it now...

        spl_state = old_splflags;

    }

    cyg_scheduler_unlock();

    return res;

}

// ------------------------------------------------------------------------

// DEBUGGING ROUTINES

#ifdef CYGIMPL_TRACE_SPLX   

#undef cyg_scheduler_lock

#undef cyg_scheduler_safe_lock

#undef cyg_scheduler_unlock

#define MAX_SCHED_EVENTS 256

static struct _sched_event {

    char *fun, *file;

    int line, lock;

} sched_event[MAX_SCHED_EVENTS];

static int next_sched_event = 0;

static int total_sched_events = 0;

static void

do_sched_event(char *fun, char *file, int line, int lock)

{

    struct _sched_event *se = &sched_event[next_sched_event];

    if (++next_sched_event == MAX_SCHED_EVENTS) {

        next_sched_event = 0;

    }

    se->fun = fun;

    se->file = file;

    se->line = line;

    se->lock = lock;

    total_sched_events++;

}

static void

show_sched_events(void)

{

    int i;

    struct _sched_event *se;

    if (total_sched_events < MAX_SCHED_EVENTS) {

        i = 0;

    } else {

        i = next_sched_event + 1;

        if (i == MAX_SCHED_EVENTS) i = 0;

    }

    diag_printf("%d total scheduler events\n", total_sched_events);

    while (i != next_sched_event) {

        se = &sched_event[i];

        diag_printf("%s - lock: %d, called from %s.%d\n", se->fun, se->lock, se->file, se->line);

        if (++i == MAX_SCHED_EVENTS) i = 0;

    }

}

#define SPLX_TRACE_DATA() cyg_scheduler_read_lock()

void

_cyg_scheduler_lock(char *file, int line)

{

    cyg_scheduler_lock();

    do_sched_event(__FUNCTION__, file, line, SPLX_TRACE_DATA());

}

void

_cyg_scheduler_safe_lock(char *file, int line)

{

    cyg_scheduler_safe_lock();

    do_sched_event(__FUNCTION__, file, line, SPLX_TRACE_DATA());

}

void

_cyg_scheduler_unlock(char *file, int line)

{

    cyg_scheduler_unlock();

    do_sched_event(__FUNCTION__, file, line, SPLX_TRACE_DATA());

}

#endif // CYGIMPL_TRACE_SPLX

// EOF synch.c