> Date: Wed, 12 Jun 2019 23:57:27 +0200 (CEST)
> From: Mark Kettenis <[email protected]>
>
> > From: "Sven M. Hallberg" <[email protected]>
> > Date: Wed, 12 Jun 2019 23:18:24 +0200
> >
> > Mark Kettenis on Tue, Jun 11 2019:
> > > The drm(4) codebase really needs multi-threaded task queues [...]
> > >
> > > The diff also starts 4 threads for each workqueue that gets created by
> > > the drm(4) layer. The number 4 is a bit arbitrary but it is the
> > > number of threads that Linux creates per CPU for a so-called "unbound"
> > > workqueue which hopefully is enough to always make progress.
> > >
> > > Please test.
> >
> > Looks good and appears to work fine with two displays (one internal, one
> > external). Will test with three at work tomorrow.
> >
> >
> > > - dev_priv->hotplug.poll_init_work.tq = systq;
> >
> > Intentional?
>
> Yes. It removes a local modification that should no longer be necessary.
>
> Unfortunately the diff doesn't work with amdgpu. Some more thinking
> needed...
So here is a diff that fixes the problem as far as I can tell.
Jonathan, Sven, can you give this a go?
Index: dev/pci/drm/drm_linux.c
===================================================================
RCS file: /cvs/src/sys/dev/pci/drm/drm_linux.c,v
retrieving revision 1.38
diff -u -p -r1.38 drm_linux.c
--- dev/pci/drm/drm_linux.c 9 Jun 2019 12:58:30 -0000 1.38
+++ dev/pci/drm/drm_linux.c 13 Jun 2019 20:53:23 -0000
@@ -1399,15 +1399,15 @@ drm_linux_init(void)
{
if (system_wq == NULL) {
system_wq = (struct workqueue_struct *)
- taskq_create("drmwq", 1, IPL_HIGH, 0);
+ taskq_create("drmwq", 4, IPL_HIGH, 0);
}
if (system_unbound_wq == NULL) {
system_unbound_wq = (struct workqueue_struct *)
- taskq_create("drmubwq", 1, IPL_HIGH, 0);
+ taskq_create("drmubwq", 4, IPL_HIGH, 0);
}
if (system_long_wq == NULL) {
system_long_wq = (struct workqueue_struct *)
- taskq_create("drmlwq", 1, IPL_HIGH, 0);
+ taskq_create("drmlwq", 4, IPL_HIGH, 0);
}
if (taskletq == NULL)
Index: dev/pci/drm/i915/intel_hotplug.c
===================================================================
RCS file: /cvs/src/sys/dev/pci/drm/i915/intel_hotplug.c,v
retrieving revision 1.2
diff -u -p -r1.2 intel_hotplug.c
--- dev/pci/drm/i915/intel_hotplug.c 14 Apr 2019 10:14:52 -0000 1.2
+++ dev/pci/drm/i915/intel_hotplug.c 13 Jun 2019 20:53:23 -0000
@@ -619,7 +619,6 @@ void intel_hpd_init_work(struct drm_i915
INIT_WORK(&dev_priv->hotplug.hotplug_work, i915_hotplug_work_func);
INIT_WORK(&dev_priv->hotplug.dig_port_work, i915_digport_work_func);
INIT_WORK(&dev_priv->hotplug.poll_init_work, i915_hpd_poll_init_work);
- dev_priv->hotplug.poll_init_work.tq = systq;
INIT_DELAYED_WORK(&dev_priv->hotplug.reenable_work,
intel_hpd_irq_storm_reenable_work);
}
Index: kern/kern_task.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_task.c,v
retrieving revision 1.25
diff -u -p -r1.25 kern_task.c
--- kern/kern_task.c 28 Apr 2019 04:20:40 -0000 1.25
+++ kern/kern_task.c 13 Jun 2019 20:53:23 -0000
@@ -43,6 +43,7 @@ struct taskq {
TQ_S_DESTROYED
} tq_state;
unsigned int tq_running;
+ unsigned int tq_waiting;
unsigned int tq_nthreads;
unsigned int tq_flags;
const char *tq_name;
@@ -59,6 +60,7 @@ static const char taskq_sys_name[] = "sy
struct taskq taskq_sys = {
TQ_S_CREATED,
0,
+ 0,
1,
0,
taskq_sys_name,
@@ -77,6 +79,7 @@ static const char taskq_sys_mp_name[] =
struct taskq taskq_sys_mp = {
TQ_S_CREATED,
0,
+ 0,
1,
TASKQ_MPSAFE,
taskq_sys_mp_name,
@@ -122,6 +125,7 @@ taskq_create(const char *name, unsigned
tq->tq_state = TQ_S_CREATED;
tq->tq_running = 0;
+ tq->tq_waiting = 0;
tq->tq_nthreads = nthreads;
tq->tq_name = name;
tq->tq_flags = flags;
@@ -223,6 +227,7 @@ taskq_barrier(struct taskq *tq)
WITNESS_CHECKORDER(&tq->tq_lock_object, LOP_NEWORDER, NULL);
+ SET(t.t_flags, TASK_BARRIER);
task_add(tq, &t);
cond_wait(&c, "tqbar");
}
@@ -238,6 +243,7 @@ taskq_del_barrier(struct taskq *tq, stru
if (task_del(tq, del))
return;
+ SET(t.t_flags, TASK_BARRIER);
task_add(tq, &t);
cond_wait(&c, "tqbar");
}
@@ -304,13 +310,26 @@ taskq_next_work(struct taskq *tq, struct
struct task *next;
mtx_enter(&tq->tq_mtx);
+retry:
while ((next = TAILQ_FIRST(&tq->tq_worklist)) == NULL) {
if (tq->tq_state != TQ_S_RUNNING) {
mtx_leave(&tq->tq_mtx);
return (0);
}
+ tq->tq_waiting++;
msleep(tq, &tq->tq_mtx, PWAIT, "bored", 0);
+ tq->tq_waiting--;
+ }
+
+ if (ISSET(next->t_flags, TASK_BARRIER)) {
+ if (++tq->tq_waiting == tq->tq_nthreads) {
+ tq->tq_waiting--;
+ } else {
+ msleep(tq, &tq->tq_mtx, PWAIT, "tqblk", 0);
+ tq->tq_waiting--;
+ goto retry;
+ }
}
TAILQ_REMOVE(&tq->tq_worklist, next, t_entry);
Index: sys/task.h
===================================================================
RCS file: /cvs/src/sys/sys/task.h,v
retrieving revision 1.15
diff -u -p -r1.15 task.h
--- sys/task.h 28 Apr 2019 04:20:40 -0000 1.15
+++ sys/task.h 13 Jun 2019 20:53:23 -0000
@@ -31,6 +31,7 @@ struct task {
};
#define TASK_ONQUEUE 1
+#define TASK_BARRIER 2
TAILQ_HEAD(task_list, task);
