6 files changed, 58 insertions, 16 deletions

diff --git a/drivers/gpu/nvgpu/common/linux/ioctl_as.c b/drivers/gpu/nvgpu/common/linux/ioctl_as.c
index 6fd0a3d2..d4242955 100644
--- a/drivers/gpu/nvgpu/common/linux/ioctl_as.c
+++ b/drivers/gpu/nvgpu/common/linux/ioctl_as.c
@@ -42,14 +42,19 @@ static int gk20a_as_ioctl_bind_channel(
         gk20a_dbg_fn("");
 
         ch = gk20a_get_channel_from_file(args->channel_fd);
-        if (!ch || gk20a_channel_as_bound(ch))
+        if (!ch)
                 return -EINVAL;
 
+        if (gk20a_channel_as_bound(ch)) {
+                err = -EINVAL;
+                goto out;
+        }
+
         /* this will set channel_gk20a->vm */
         err = ch->g->ops.mm.vm_bind_channel(as_share, ch);
-        if (err)
-                return err;
 
+out:
+        gk20a_channel_put(ch);
         return err;
 }
 
diff --git a/drivers/gpu/nvgpu/common/linux/ioctl_channel.c b/drivers/gpu/nvgpu/common/linux/ioctl_channel.c
index ab02dc42..5e09c677 100644
--- a/drivers/gpu/nvgpu/common/linux/ioctl_channel.c
+++ b/drivers/gpu/nvgpu/common/linux/ioctl_channel.c
@@ -260,8 +260,15 @@ static int gk20a_init_error_notifier(struct channel_gk20a *ch,
         return 0;
 }
 
+/*
+ * This returns the channel with a reference. The caller must
+ * gk20a_channel_put() the ref back after use.
+ *
+ * NULL is returned if the channel was not found.
+ */
 struct channel_gk20a *gk20a_get_channel_from_file(int fd)
 {
+        struct channel_gk20a *ch;
         struct channel_priv *priv;
         struct file *f = fget(fd);
 
@@ -274,8 +281,9 @@ struct channel_gk20a *gk20a_get_channel_from_file(int fd)
         }
 
         priv = (struct channel_priv *)f->private_data;
+        ch = gk20a_channel_get(priv->c);
         fput(f);
-        return priv->c;
+        return ch;
 }
 
 int gk20a_channel_release(struct inode *inode, struct file *filp)
diff --git a/drivers/gpu/nvgpu/common/linux/ioctl_ctrl.c b/drivers/gpu/nvgpu/common/linux/ioctl_ctrl.c
index 2c274f23..0d79b143 100644
--- a/drivers/gpu/nvgpu/common/linux/ioctl_ctrl.c
+++ b/drivers/gpu/nvgpu/common/linux/ioctl_ctrl.c
@@ -354,6 +354,8 @@ static int nvgpu_gpu_ioctl_inval_icache(
         nvgpu_mutex_acquire(&g->dbg_sessions_lock);
         err = g->ops.gr.inval_icache(g, ch);
         nvgpu_mutex_release(&g->dbg_sessions_lock);
+
+        gk20a_channel_put(ch);
         return err;
 }
 
@@ -393,6 +395,7 @@ static int nvgpu_gpu_ioctl_set_debug_mode(
                 err = -ENOSYS;
         nvgpu_mutex_release(&g->dbg_sessions_lock);
 
+        gk20a_channel_put(ch);
         return err;
 }
 
diff --git a/drivers/gpu/nvgpu/common/linux/ioctl_tsg.c b/drivers/gpu/nvgpu/common/linux/ioctl_tsg.c
index c68c907e..d35ea14c 100644
--- a/drivers/gpu/nvgpu/common/linux/ioctl_tsg.c
+++ b/drivers/gpu/nvgpu/common/linux/ioctl_tsg.c
@@ -49,6 +49,8 @@ static int gk20a_tsg_bind_channel_fd(struct tsg_gk20a *tsg, int ch_fd)
                 return -EINVAL;
 
         err = ch->g->ops.fifo.tsg_bind_channel(tsg, ch);
+
+        gk20a_channel_put(ch);
         return err;
 }
 
diff --git a/drivers/gpu/nvgpu/gk20a/dbg_gpu_gk20a.c b/drivers/gpu/nvgpu/gk20a/dbg_gpu_gk20a.c
index 00050850..19433df9 100644
--- a/drivers/gpu/nvgpu/gk20a/dbg_gpu_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/dbg_gpu_gk20a.c
@@ -514,7 +514,8 @@ static int dbg_unbind_channel_gk20a(struct dbg_session_gk20a *dbg_s,
 
         if (!channel_found) {
                 gk20a_dbg_fn("channel not bounded, fd=%d\n", args->channel_fd);
-                return -EINVAL;
+                err = -EINVAL;
+                goto out;
         }
 
         nvgpu_mutex_acquire(&g->dbg_sessions_lock);
@@ -523,6 +524,8 @@ static int dbg_unbind_channel_gk20a(struct dbg_session_gk20a *dbg_s,
         nvgpu_mutex_release(&dbg_s->ch_list_lock);
         nvgpu_mutex_release(&g->dbg_sessions_lock);
 
+out:
+        gk20a_channel_put(ch);
         return err;
 }
 
@@ -584,13 +587,16 @@ static int dbg_bind_channel_gk20a(struct dbg_session_gk20a *dbg_s,
         struct channel_gk20a *ch;
         struct dbg_session_channel_data *ch_data;
         struct dbg_session_data *session_data;
+        int err = 0;
 
         gk20a_dbg(gpu_dbg_fn|gpu_dbg_gpu_dbg, "%s fd=%d",
                    g->name, args->channel_fd);
 
-        /* even though get_file_channel is doing this it releases it as well */
-        /* by holding it here we'll keep it from disappearing while the
-         * debugger is in session */
+        /*
+         * Although gk20a_get_channel_from_file gives us a channel ref, need to
+         * hold a ref to the file during the session lifetime. See comment in
+         * struct dbg_session_channel_data.
+         */
         f = fget(args->channel_fd);
         if (!f)
                 return -ENODEV;
@@ -598,8 +604,8 @@ static int dbg_bind_channel_gk20a(struct dbg_session_gk20a *dbg_s,
         ch = gk20a_get_channel_from_file(args->channel_fd);
         if (!ch) {
                 gk20a_dbg_fn("no channel found for fd");
-                fput(f);
-                return -EINVAL;
+                err = -EINVAL;
+                goto out_fput;
         }
 
         gk20a_dbg_fn("%s hwchid=%d", g->name, ch->chid);
@@ -609,8 +615,8 @@ static int dbg_bind_channel_gk20a(struct dbg_session_gk20a *dbg_s,
 
         ch_data = nvgpu_kzalloc(g, sizeof(*ch_data));
         if (!ch_data) {
-                fput(f);
-                return -ENOMEM;
+                err = -ENOMEM;
+                goto out_chput;
         }
         ch_data->ch_f = f;
         ch_data->channel_fd = args->channel_fd;
@@ -619,9 +625,8 @@ static int dbg_bind_channel_gk20a(struct dbg_session_gk20a *dbg_s,
 
         session_data = nvgpu_kzalloc(g, sizeof(*session_data));
         if (!session_data) {
-                nvgpu_kfree(g, ch_data);
-                fput(f);
-                return -ENOMEM;
+                err = -ENOMEM;
+                goto out_kfree;
         }
         session_data->dbg_s = dbg_s;
         nvgpu_init_list_node(&session_data->dbg_s_entry);
@@ -636,7 +641,19 @@ static int dbg_bind_channel_gk20a(struct dbg_session_gk20a *dbg_s,
         nvgpu_mutex_release(&ch->dbg_s_lock);
         nvgpu_mutex_release(&g->dbg_sessions_lock);
 
+        gk20a_channel_put(ch);
+
         return 0;
+
+out_kfree:
+        nvgpu_kfree(g, ch_data);
+out_chput:
+        gk20a_channel_put(ch);
+        nvgpu_mutex_release(&ch->dbg_s_lock);
+        nvgpu_mutex_release(&g->dbg_sessions_lock);
+out_fput:
+        fput(f);
+        return err;
 }
 
 static int nvgpu_ioctl_channel_reg_ops(struct dbg_session_gk20a *dbg_s,
diff --git a/drivers/gpu/nvgpu/gk20a/dbg_gpu_gk20a.h b/drivers/gpu/nvgpu/gk20a/dbg_gpu_gk20a.h
index 827fb42f..4d2c0f94 100644
--- a/drivers/gpu/nvgpu/gk20a/dbg_gpu_gk20a.h
+++ b/drivers/gpu/nvgpu/gk20a/dbg_gpu_gk20a.h
@@ -93,7 +93,14 @@ dbg_session_data_from_dbg_s_entry(struct nvgpu_list_node *node)
 };
 
 struct dbg_session_channel_data {
-        struct file          *ch_f;
+        /*
+         * We have to keep a ref to the _file_, not the channel, because
+         * close(channel_fd) is synchronous and would deadlock if we had an
+         * open debug session fd holding a channel ref at that time. Holding a
+         * ref to the file makes close(channel_fd) just drop a kernel ref to
+         * the file; the channel will close when the last file ref is dropped.
+         */
+        struct file *ch_f;
         int channel_fd;
         int chid;
         struct nvgpu_list_node ch_entry;