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futex(): spin wait when CPU not oversubscribed and fix lost wake-up bug

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This commit is contained in:
Balazs Gerofi
2017-01-12 18:50:21 +09:00
parent d646c2a4b9
commit bd47b909bf
7 changed files with 163 additions and 142 deletions
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72
kernel/process.c
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@ -2668,6 +2668,65 @@ set_timer()
}
}
/*
* NOTE: it is assumed that a wait-queue (or futex queue) is
* set before calling this function.
* NOTE: one must set thread->spin_sleep to 1 before evaluating
* the wait condition to avoid lost wake-ups.
*/
void spin_sleep_or_schedule(void)
{
struct thread *thread = cpu_local_var(current);
struct cpu_local_var *v;
int do_schedule = 0;
int woken = 0;
long irqstate;
/* Try to spin sleep */
irqstate = ihk_mc_spinlock_lock(&thread->spin_sleep_lock);
if (thread->spin_sleep == 0) {
dkprintf("%s: caught a lost wake-up!\n", __FUNCTION__);
}
ihk_mc_spinlock_unlock(&thread->spin_sleep_lock, irqstate);
for (;;) {
/* Check if we need to reschedule */
irqstate =
ihk_mc_spinlock_lock(&(get_this_cpu_local_var()->runq_lock));
v = get_this_cpu_local_var();
if (v->flags & CPU_FLAG_NEED_RESCHED || v->runq_len > 1) {
do_schedule = 1;
}
ihk_mc_spinlock_unlock(&v->runq_lock, irqstate);
/* Check if we were woken up */
irqstate = ihk_mc_spinlock_lock(&thread->spin_sleep_lock);
if (thread->spin_sleep == 0) {
woken = 1;
}
/* Indicate that we are not spinning any more */
if (do_schedule) {
thread->spin_sleep = 0;
}
ihk_mc_spinlock_unlock(&thread->spin_sleep_lock, irqstate);
if (woken) {
return;
}
if (do_schedule) {
break;
}
cpu_pause();
}
schedule();
}
void schedule(void)
{
struct cpu_local_var *v;
@ -2834,7 +2893,6 @@ int
sched_wakeup_thread(struct thread *thread, int valid_states)
{
int status;
int spin_slept = 0;
unsigned long irqstate;
struct cpu_local_var *v = get_cpu_local_var(thread->cpu_id);
struct process *proc = thread->proc;
@ -2844,29 +2902,23 @@ sched_wakeup_thread(struct thread *thread, int valid_states)
proc->pid, valid_states, thread->status, thread->cpu_id, ihk_mc_get_processor_id());
irqstate = ihk_mc_spinlock_lock(&(thread->spin_sleep_lock));
if (thread->spin_sleep > 0) {
if (thread->spin_sleep == 1) {
dkprintf("sched_wakeup_process() spin wakeup: cpu_id: %d\n",
thread->cpu_id);
spin_slept = 1;
status = 0;
}
--thread->spin_sleep;
thread->spin_sleep = 0;
ihk_mc_spinlock_unlock(&(thread->spin_sleep_lock), irqstate);
if (spin_slept) {
return status;
}
irqstate = ihk_mc_spinlock_lock(&(v->runq_lock));
if (thread->status & valid_states) {
mcs_rwlock_writer_lock_noirq(&proc->update_lock, &updatelock);
if(proc->status != PS_EXITED)
if (proc->status != PS_EXITED)
proc->status = PS_RUNNING;
mcs_rwlock_writer_unlock_noirq(&proc->update_lock, &updatelock);
xchg4((int *)(&thread->status), PS_RUNNING);
barrier();
status = 0;
}
else {