1 files changed, 39 insertions, 13 deletions

diff --git a/drivers/gpu/nvgpu/os/linux/ioctl_ctrl.c b/drivers/gpu/nvgpu/os/linux/ioctl_ctrl.c
index f71921cb..b6cdffcb 100644
--- a/drivers/gpu/nvgpu/os/linux/ioctl_ctrl.c
+++ b/drivers/gpu/nvgpu/os/linux/ioctl_ctrl.c
@@ -2051,7 +2051,7 @@ int gk20a_ctrl_dev_mmap(struct file *filp, struct vm_area_struct *vma)
         return err;
 }
 
-static void alter_usermode_mapping(struct gk20a *g,
+static int alter_usermode_mapping(struct gk20a *g,
                 struct gk20a_ctrl_priv *priv,
                 bool poweroff)
 {
@@ -2059,23 +2059,34 @@ static void alter_usermode_mapping(struct gk20a *g,
         struct vm_area_struct *vma = priv->usermode_vma.vma;
         bool vma_mapped = priv->usermode_vma.vma_mapped;
         u64 addr;
-        int err;
+        int err = 0;
 
         if (!vma) {
                 /* Nothing to do - no mmap called */
-                return;
+                return 0;
         }
 
         addr = l->regs_bus_addr + g->ops.fifo.usermode_base(g);
 
-        down_write(&vma->vm_mm->mmap_sem);
-
         /*
          * This is a no-op for the below cases
          * a) poweroff and !vma_mapped - > do nothing as no map exists
          * b) !poweroff and vmap_mapped -> do nothing as already mapped
          */
-        if (poweroff && vma_mapped) {
+        if (poweroff != vma_mapped) {
+                return 0;
+        }
+
+        /*
+         * We use trylock due to lock inversion: we need to acquire
+         * mmap_lock while holding ctrl_privs_lock. usermode_vma_close
+         * does it in reverse order. Trylock is a way to avoid deadlock.
+         */
+        if (!down_write_trylock(&vma->vm_mm->mmap_sem)) {
+                return -EBUSY;
+        }
+
+        if (poweroff) {
                 err = zap_vma_ptes(vma, vma->vm_start, SZ_4K);
                 if (err == 0) {
                         vma->vm_flags = VM_NONE;
@@ -2083,7 +2094,7 @@ static void alter_usermode_mapping(struct gk20a *g,
                 } else {
                         nvgpu_err(g, "can't remove usermode mapping");
                 }
-        } else if (!poweroff && !vma_mapped) {
+        } else {
                 vma->vm_flags = priv->usermode_vma.flags;
                 err = io_remap_pfn_range(vma, vma->vm_start,
                                 addr >> PAGE_SHIFT,
@@ -2097,19 +2108,34 @@ static void alter_usermode_mapping(struct gk20a *g,
         }
 
         up_write(&vma->vm_mm->mmap_sem);
+
+        return err;
 }
 
 static void alter_usermode_mappings(struct gk20a *g, bool poweroff)
 {
         struct gk20a_ctrl_priv *priv;
         struct nvgpu_os_linux *l = nvgpu_os_linux_from_gk20a(g);
+        int err = 0;
 
-        nvgpu_mutex_acquire(&l->ctrl.privs_lock);
-        nvgpu_list_for_each_entry(priv, &l->ctrl.privs,
-                        gk20a_ctrl_priv, list) {
-                alter_usermode_mapping(g, priv, poweroff);
-        }
-        nvgpu_mutex_release(&l->ctrl.privs_lock);
+        do {
+                nvgpu_mutex_acquire(&l->ctrl.privs_lock);
+                nvgpu_list_for_each_entry(priv, &l->ctrl.privs,
+                                gk20a_ctrl_priv, list) {
+                        err = alter_usermode_mapping(g, priv, poweroff);
+                        if (err != 0) {
+                                break;
+                        }
+                }
+                nvgpu_mutex_release(&l->ctrl.privs_lock);
+
+                if (err == -EBUSY) {
+                        nvgpu_log_info(g, "ctrl_privs_lock lock contended. retry altering usermode mappings");
+                        nvgpu_udelay(10);
+                } else if (err != 0) {
+                        nvgpu_err(g, "can't alter usermode mapping. err = %d", err);
+                }
+        } while (err == -EBUSY);
 }
 
 void nvgpu_hide_usermode_for_poweroff(struct gk20a *g)