76092ddf33
This can be turned back on when the library is compiled with -DMTHREAD_STRICT (which enables more sanity checks). However, always performing this check shows up in system profiling results.
217 lines
6.8 KiB
C
217 lines
6.8 KiB
C
#include <minix/mthread.h>
|
|
#include "global.h"
|
|
#include "proto.h"
|
|
|
|
#define MAIN_CTX &(mainthread.m_context)
|
|
#define MAIN_STATE mainthread.m_state
|
|
#define OLD_CTX &(threads[old_thread]->m_context)
|
|
#define CURRENT_CTX &(threads[current_thread]->m_context)
|
|
#define CURRENT_STATE threads[current_thread]->m_state
|
|
static int yield_all;
|
|
|
|
/*===========================================================================*
|
|
* mthread_getcontext *
|
|
*===========================================================================*/
|
|
int mthread_getcontext(ctx)
|
|
ucontext_t *ctx;
|
|
{
|
|
/* Retrieve this process' current state.*/
|
|
|
|
/* We're not interested in FPU state nor signals, so ignore them.
|
|
* Coincidentally, this significantly speeds up performance.
|
|
*/
|
|
ctx->uc_flags |= (UCF_IGNFPU | UCF_IGNSIGM);
|
|
return getcontext(ctx);
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* mthread_schedule *
|
|
*===========================================================================*/
|
|
void mthread_schedule(void)
|
|
{
|
|
/* Pick a new thread to run and run it. In practice, this involves taking the
|
|
* first thread off the (FIFO) run queue and resuming that thread.
|
|
*/
|
|
|
|
mthread_thread_t old_thread;
|
|
mthread_tcb_t *new_tcb, *old_tcb;
|
|
ucontext_t *new_ctx, *old_ctx;
|
|
|
|
MTHREAD_CHECK_INIT(); /* Make sure libmthread is initialized */
|
|
|
|
old_thread = current_thread;
|
|
|
|
if (mthread_queue_isempty(&run_queue)) {
|
|
/* No runnable threads. Let main thread run. */
|
|
|
|
/* We keep track whether we're running the program's 'main' thread or
|
|
* a spawned thread. In case we're already running the main thread and
|
|
* there are no runnable threads, we can't jump back to its context.
|
|
* Instead, we simply return.
|
|
*/
|
|
if (running_main_thread) return;
|
|
|
|
/* We're running the last runnable spawned thread. Return to main
|
|
* thread as there is no work left.
|
|
*/
|
|
current_thread = MAIN_THREAD;
|
|
} else {
|
|
current_thread = mthread_queue_remove(&run_queue);
|
|
}
|
|
|
|
/* Find thread entries in tcb... */
|
|
new_tcb = mthread_find_tcb(current_thread);
|
|
old_tcb = mthread_find_tcb(old_thread);
|
|
|
|
/* ...and subsequently their contexts */
|
|
new_ctx = &(new_tcb->m_context);
|
|
old_ctx = &(old_tcb->m_context);
|
|
|
|
/* Are we running the 'main' thread after swap? */
|
|
running_main_thread = (current_thread == MAIN_THREAD);
|
|
|
|
if (swapcontext(old_ctx, new_ctx) == -1)
|
|
mthread_panic("Could not swap context");
|
|
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* mthread_init_scheduler *
|
|
*===========================================================================*/
|
|
void mthread_init_scheduler(void)
|
|
{
|
|
/* Initialize the scheduler */
|
|
mthread_queue_init(&run_queue);
|
|
yield_all = 0;
|
|
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* mthread_suspend *
|
|
*===========================================================================*/
|
|
void mthread_suspend(state)
|
|
mthread_state_t state;
|
|
{
|
|
/* Stop the current thread from running. There can be multiple reasons for
|
|
* this; the process tries to lock a locked mutex (i.e., has to wait for it to
|
|
* become unlocked), the process has to wait for a condition, the thread
|
|
* volunteered to let another thread to run (i.e., it called yield and remains
|
|
* runnable itself), or the thread is dead.
|
|
*/
|
|
|
|
int continue_thread = 0;
|
|
mthread_tcb_t *tcb;
|
|
ucontext_t *ctx;
|
|
|
|
if (state == MS_DEAD) mthread_panic("Shouldn't suspend with MS_DEAD state");
|
|
tcb = mthread_find_tcb(current_thread);
|
|
tcb->m_state = state;
|
|
ctx = &(tcb->m_context);
|
|
|
|
/* Save current thread's context */
|
|
if (mthread_getcontext(ctx) != 0)
|
|
mthread_panic("Couldn't save current thread's context");
|
|
|
|
/* We return execution here with setcontext/swapcontext, but also when we
|
|
* simply return from the getcontext call. If continue_thread is non-zero, we
|
|
* are continuing the execution of this thread after a call from setcontext
|
|
* or swapcontext.
|
|
*/
|
|
|
|
if(!continue_thread) {
|
|
continue_thread = 1;
|
|
mthread_schedule(); /* Let other thread run. */
|
|
}
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* mthread_unsuspend *
|
|
*===========================================================================*/
|
|
void mthread_unsuspend(thread)
|
|
mthread_thread_t thread; /* Thread to make runnable */
|
|
{
|
|
/* Mark the state of a thread runnable and add it to the run queue */
|
|
mthread_tcb_t *tcb;
|
|
|
|
if (!isokthreadid(thread)) mthread_panic("Invalid thread id");
|
|
|
|
tcb = mthread_find_tcb(thread);
|
|
tcb->m_state = MS_RUNNABLE;
|
|
mthread_queue_add(&run_queue, thread);
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* mthread_yield *
|
|
*===========================================================================*/
|
|
int mthread_yield(void)
|
|
{
|
|
/* Defer further execution of the current thread and let another thread run. */
|
|
mthread_tcb_t *tcb;
|
|
mthread_thread_t t;
|
|
|
|
MTHREAD_CHECK_INIT(); /* Make sure libmthread is initialized */
|
|
|
|
/* Detached threads cannot clean themselves up. This is a perfect moment to
|
|
* do it */
|
|
for (t = (mthread_thread_t) 0; need_reset > 0 && t < no_threads; t++) {
|
|
tcb = mthread_find_tcb(t);
|
|
if (tcb->m_state == MS_NEEDRESET) {
|
|
mthread_thread_reset(t);
|
|
used_threads--;
|
|
need_reset--;
|
|
mthread_queue_add(&free_threads, t);
|
|
}
|
|
}
|
|
|
|
if (mthread_queue_isempty(&run_queue)) { /* No point in yielding. */
|
|
return(-1);
|
|
} else if (current_thread == NO_THREAD) {
|
|
/* Can't yield this thread */
|
|
return(-1);
|
|
}
|
|
|
|
mthread_queue_add(&run_queue, current_thread);
|
|
mthread_suspend(MS_RUNNABLE); /* We're still runnable, but we're just kind
|
|
* enough to let someone else run.
|
|
*/
|
|
return(0);
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* mthread_yield_all *
|
|
*===========================================================================*/
|
|
void mthread_yield_all(void)
|
|
{
|
|
/* Yield until there are no more runnable threads left. Two threads calling
|
|
* this function will lead to a deadlock.
|
|
*/
|
|
|
|
MTHREAD_CHECK_INIT(); /* Make sure libmthread is initialized */
|
|
|
|
if (yield_all) mthread_panic("Deadlock: two threads trying to yield_all");
|
|
yield_all = 1;
|
|
|
|
/* This works as follows. Thread A is running and threads B, C, and D are
|
|
* runnable. As A is running, it is NOT on the run_queue (see
|
|
* mthread_schedule). It calls mthread_yield and will be added to the run
|
|
* queue, allowing B to run. B runs and suspends eventually, possibly still
|
|
* in a runnable state. Then C and D run. Eventually A will run again (and is
|
|
* thus not on the list). If B, C, and D are dead, waiting for a condition,
|
|
* or waiting for a lock, they are not on the run queue either. At that
|
|
* point A is the only runnable thread left.
|
|
*/
|
|
while (!mthread_queue_isempty(&run_queue)) {
|
|
(void) mthread_yield();
|
|
}
|
|
|
|
/* Done yielding all threads. */
|
|
yield_all = 0;
|
|
}
|
|
|