nouveau: push event block/allowing out of the fence context

There is a deadlock between the irq and fctx locks,
the irq handling takes irq then fctx lock
the fence signalling takes fctx then irq lock

This splits the fence signalling path so the code that hits
the irq lock is done in a separate work queue.

This seems to fix crashes/hangs when using nouveau gsp with
i915 primary GPU.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231222043308.3090089-11-airlied@gmail.com

diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c b/drivers/gpu/drm/nouveau/nouveau_fence.c
index ca762ea5541361bb023e8b0288470502797f1a15..5057d976fa578cebe2e9e847c6e78634d2b08968 100644 (file)
--- a/drivers/gpu/drm/nouveau/nouveau_fence.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
@@ -62,7 +62,7 @@ nouveau_fence_signal(struct nouveau_fence *fence)
        if (test_bit(DMA_FENCE_FLAG_USER_BITS, &fence->base.flags)) {
                struct nouveau_fence_chan *fctx = nouveau_fctx(fence);
 
-               if (!--fctx->notify_ref)
+               if (atomic_dec_and_test(&fctx->notify_ref))
                        drop = 1;
        }
 
@@ -103,6 +103,7 @@ nouveau_fence_context_kill(struct nouveau_fence_chan *fctx, int error)
 void
 nouveau_fence_context_del(struct nouveau_fence_chan *fctx)
 {
+       cancel_work_sync(&fctx->allow_block_work);
        nouveau_fence_context_kill(fctx, 0);
        nvif_event_dtor(&fctx->event);
        fctx->dead = 1;
@@ -167,6 +168,18 @@ nouveau_fence_wait_uevent_handler(struct nvif_event *event, void *repv, u32 repc
        return ret;
 }
 
+static void
+nouveau_fence_work_allow_block(struct work_struct *work)
+{
+       struct nouveau_fence_chan *fctx = container_of(work, struct nouveau_fence_chan,
+                                                      allow_block_work);
+
+       if (atomic_read(&fctx->notify_ref) == 0)
+               nvif_event_block(&fctx->event);
+       else
+               nvif_event_allow(&fctx->event);
+}
+
 void
 nouveau_fence_context_new(struct nouveau_channel *chan, struct nouveau_fence_chan *fctx)
 {
@@ -178,6 +191,7 @@ nouveau_fence_context_new(struct nouveau_channel *chan, struct nouveau_fence_cha
        } args;
        int ret;
 
+       INIT_WORK(&fctx->allow_block_work, nouveau_fence_work_allow_block);
        INIT_LIST_HEAD(&fctx->flip);
        INIT_LIST_HEAD(&fctx->pending);
        spin_lock_init(&fctx->lock);
@@ -521,15 +535,19 @@ static bool nouveau_fence_enable_signaling(struct dma_fence *f)
        struct nouveau_fence *fence = from_fence(f);
        struct nouveau_fence_chan *fctx = nouveau_fctx(fence);
        bool ret;
+       bool do_work;
 
-       if (!fctx->notify_ref++)
-               nvif_event_allow(&fctx->event);
+       if (atomic_inc_return(&fctx->notify_ref) == 0)
+               do_work = true;
 
        ret = nouveau_fence_no_signaling(f);
        if (ret)
                set_bit(DMA_FENCE_FLAG_USER_BITS, &fence->base.flags);
-       else if (!--fctx->notify_ref)
-               nvif_event_block(&fctx->event);
+       else if (atomic_dec_and_test(&fctx->notify_ref))
+               do_work = true;
+
+       if (do_work)
+               schedule_work(&fctx->allow_block_work);
 
        return ret;
 }

diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.h b/drivers/gpu/drm/nouveau/nouveau_fence.h
index 64d33ae7f35610fe763cd34f717335ab7b24ea4e..28f5cf013b8983240204d028c8367249a63912e0 100644 (file)
--- a/drivers/gpu/drm/nouveau/nouveau_fence.h
+++ b/drivers/gpu/drm/nouveau/nouveau_fence.h
@@ -3,6 +3,7 @@
 #define __NOUVEAU_FENCE_H__
 
 #include <linux/dma-fence.h>
+#include <linux/workqueue.h>
 #include <nvif/event.h>
 
 struct nouveau_drm;
@@ -45,7 +46,9 @@ struct nouveau_fence_chan {
        char name[32];
 
        struct nvif_event event;
-       int notify_ref, dead, killed;
+       struct work_struct allow_block_work;
+       atomic_t notify_ref;
+       int dead, killed;
 };
 
 struct nouveau_fence_priv {