gpu: nvgpu: cde: restrict context count

Add an upper limit for cde contexts, and wait for a while if a new
context is queried and the limit has been exceeded. This happens only
under very high load. If the timeout is exceeded, report -EAGAIN.

Change-Id: I1fa47ad6cddf620eae00cea16ecea36cf4151cab
Signed-off-by: Konsta Holtta <kholtta@nvidia.com>
Reviewed-on: http://git-master/r/601719
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>

1 files changed, 31 insertions, 1 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/cde_gk20a.c b/drivers/gpu/nvgpu/gk20a/cde_gk20a.c
index 65d6dd4d..c96225c7 100644
--- a/drivers/gpu/nvgpu/gk20a/cde_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/cde_gk20a.c
@@ -39,6 +39,9 @@ static struct gk20a_cde_ctx *gk20a_cde_allocate_context(struct gk20a *g);
 
 #define CTX_DELETE_TIME 1000
 
+#define MAX_CTX_USE_COUNT 42
+#define MAX_CTX_RETRY_TIME 2000
+
 static void gk20a_deinit_cde_img(struct gk20a_cde_ctx *cde_ctx)
 {
         struct device *dev = &cde_ctx->pdev->dev;
@@ -782,12 +785,17 @@ out:
         gk20a_idle(pdev);
 }
 
-static struct gk20a_cde_ctx *gk20a_cde_get_context(struct gk20a *g)
+static struct gk20a_cde_ctx *gk20a_cde_do_get_context(struct gk20a *g)
 __must_hold(&cde_app->mutex)
 {
         struct gk20a_cde_app *cde_app = &g->cde_app;
         struct gk20a_cde_ctx *cde_ctx;
 
+        /* exhausted? */
+
+        if (cde_app->ctx_usecount >= MAX_CTX_USE_COUNT)
+                return ERR_PTR(-EAGAIN);
+
         /* idle context available? */
 
         if (!list_empty(&cde_app->free_contexts)) {
@@ -834,6 +842,28 @@ __must_hold(&cde_app->mutex)
         return cde_ctx;
 }
 
+static struct gk20a_cde_ctx *gk20a_cde_get_context(struct gk20a *g)
+__releases(&cde_app->mutex)
+__acquires(&cde_app->mutex)
+{
+        struct gk20a_cde_app *cde_app = &g->cde_app;
+        struct gk20a_cde_ctx *cde_ctx = NULL;
+        unsigned long end = jiffies + msecs_to_jiffies(MAX_CTX_RETRY_TIME);
+
+        do {
+                cde_ctx = gk20a_cde_do_get_context(g);
+                if (PTR_ERR(cde_ctx) != -EAGAIN)
+                        break;
+
+                /* exhausted, retry */
+                mutex_unlock(&cde_app->mutex);
+                cond_resched();
+                mutex_lock(&cde_app->mutex);
+        } while (time_before(jiffies, end));
+
+        return cde_ctx;
+}
+
 static struct gk20a_cde_ctx *gk20a_cde_allocate_context(struct gk20a *g)
 {
         struct gk20a_cde_ctx *cde_ctx;