nvmap: page pool: fix background thread

Fix a race condition in the background allocator where
wake_up_process could be called just before set_current_state
changed the state to TASK_INTERRUPTIBLE, causing the thread
not to wake.  Use a waitqueue instead.

Also make the background allocator nicer by marking it freezable
so it doesn't compete with suspend, and setting it SCHED_IDLE so
it only runs when no other threads want to run.

Change-Id: If95da005bb1fc4c9b5e802d40730803a57057fe1
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Krishna Reddy <vdumpa@nvidia.com>
Reviewed-on: http://git-master/r/664673
GVS: Gerrit_Virtual_Submit
Reviewed-on: http://git-master/r/736427
Reviewed-by: Alex Waterman <alexw@nvidia.com>
Tested-by: Alex Waterman <alexw@nvidia.com>

2 files changed, 27 insertions, 38 deletions

diff --git a/drivers/video/tegra/nvmap/nvmap_pp.c b/drivers/video/tegra/nvmap/nvmap_pp.c
index 1c2e1f715aff..c00d9f20edd4 100644
--- a/drivers/video/tegra/nvmap/nvmap_pp.c
+++ b/drivers/video/tegra/nvmap/nvmap_pp.c
@@ -28,6 +28,8 @@
 #include <linux/shrinker.h>
 #include <linux/kthread.h>
 #include <linux/debugfs.h>
+#include <linux/freezer.h>
+#include <linux/highmem.h>
 
 #include "nvmap_priv.h"
 
@@ -39,6 +41,7 @@ static bool enable_pp = 1;
 static int pool_size;
 
 static struct task_struct *background_allocator;
+static DECLARE_WAIT_QUEUE_HEAD(nvmap_bg_wait);
 static struct page *pending_pages[PENDING_PAGES_SIZE];
 static atomic_t bg_pages_to_fill;
 
@@ -74,6 +77,17 @@ static inline struct page *get_page_list_page(struct nvmap_page_pool *pool)
 	return page;
 }
 
+static inline bool nvmap_bg_should_run(struct nvmap_page_pool *pool)
+{
+	bool ret;
+
+	mutex_lock(&pool->lock);
+	ret = (pool->to_zero > 0 || atomic_read(&bg_pages_to_fill));
+	mutex_unlock(&pool->lock);
+
+	return ret;
+}
+
 /*
  * Allocate n pages one by one. Not the most efficient allocation scheme ever;
  * however, it will make it easier later on to handle single or small number of
@@ -155,17 +169,20 @@ static void nvmap_pp_do_background_fill(struct nvmap_page_pool *pool)
  */
 static int nvmap_background_zero_allocator(void *arg)
 {
+	struct nvmap_page_pool *pool = &nvmap_dev->pool;
+	struct sched_param param = { .sched_priority = 0 };
+
 	pr_info("PP alloc thread starting.\n");
 
-	while (1) {
-		if (kthread_should_stop())
-			break;
+	set_freezable();
+	sched_setscheduler(current, SCHED_IDLE, &param);
 
-		nvmap_pp_do_background_fill(&nvmap_dev->pool);
+	while (!kthread_should_stop()) {
+		nvmap_pp_do_background_fill(pool);
 
-		/* Pending work is done - go to sleep. */
-		set_current_state(TASK_INTERRUPTIBLE);
-		schedule();
+		wait_event_freezable(nvmap_bg_wait,
+				nvmap_bg_should_run(pool) ||
+				kthread_should_stop());
 	}
 
 	return 0;
@@ -206,7 +223,7 @@ static inline void nvmap_pp_wake_up_allocator(void)
 	/* Let the background thread know how much memory to fill. */
 	atomic_set(&bg_pages_to_fill,
 		   min(tmp, (int)(pool->max - pool->count)));
-	wake_up_process(background_allocator);
+	wake_up_interruptible(&nvmap_bg_wait);
 }
 
 /*
@@ -617,12 +634,6 @@ int nvmap_page_pool_init(struct nvmap_device *dev)
 	unsigned long totalram_mb;
 	struct sysinfo info;
 	struct nvmap_page_pool *pool = &dev->pool;
-#ifdef CONFIG_NVMAP_PAGE_POOLS_INIT_FILLUP
-	int i;
-	struct page *page;
-	int pages_to_fill;
-	int highmem_pages = 0;
-#endif
 
 	memset(pool, 0x0, sizeof(*pool));
 	mutex_init(&pool->lock);
@@ -655,30 +666,6 @@ int nvmap_page_pool_init(struct nvmap_device *dev)
 	if (IS_ERR_OR_NULL(background_allocator))
 		goto fail;
 
-#ifdef CONFIG_NVMAP_PAGE_POOLS_INIT_FILLUP
-	pages_to_fill = CONFIG_NVMAP_PAGE_POOLS_INIT_FILLUP_SIZE * SZ_1M /
-			PAGE_SIZE;
-	pages_to_fill = pages_to_fill ? : pool->count;
-
-	for (i = 0; i < pages_to_fill; i++) {
-		page = alloc_page(GFP_NVMAP);
-		if (!page)
-			goto done;
-		if (!nvmap_page_pool_fill_locked(pool, page)) {
-			__free_page(page);
-			goto done;
-		}
-		if (PageHighMem(page))
-			highmem_pages++;
-	}
-
-	si_meminfo(&info);
-	pr_info("highmem=%d, pool_size=%d,"
-		"totalram=%lu, freeram=%lu, totalhigh=%lu, freehigh=%lu\n",
-		highmem_pages, pool->count,
-		info.totalram, info.freeram, info.totalhigh, info.freehigh);
-done:
-#endif
 	return 0;
 fail:
 	nvmap_page_pool_fini(dev);
diff --git a/drivers/video/tegra/nvmap/nvmap_priv.h b/drivers/video/tegra/nvmap/nvmap_priv.h
index 27cb3290a599..8b715b42faac 100644
--- a/drivers/video/tegra/nvmap/nvmap_priv.h
+++ b/drivers/video/tegra/nvmap/nvmap_priv.h
@@ -173,7 +173,9 @@ struct nvmap_page_pool {
 	struct mutex lock;
 	u32 count;  /* Number of pages in the page list. */
 	u32 max;    /* Max length of the page list. */
+	int to_zero; /* Number of pages on the zero list */
 	struct list_head page_list;
+	struct list_head zero_list;
 
 #ifdef CONFIG_NVMAP_PAGE_POOL_DEBUG
 	u64 allocs;