gpu: nvgpu: Convert VIDMEM work_struct to thread

Convert the work_struct used by the vidmem background clearing to
a thread to make it more cross platform. The thread waits on a
condition variable to determine when work needs to be done. The
signal comes from the DMA API when it enqueues a new nvgpu_mem that
needs clearing.

Add logic for handling suspend: the CE cannot be accessed while
the GPU is suspended. As such the background thread must be paused
while the GPU is suspended and the CE is not available.

Several other changes were also made:

  o  Move the code that enqueues a nvgpu_mem from the DMA API
     code to a function in the VIDMEM code.
  o  Move nvgpu_vidmem_get_pending_alloc() to the Linux specific
     code as this function is only used there. It's a trivial
     function that QNX can easily implement as well.
  o  Remove the was_empty logic from the enqueue. Now just always
     signal the condition variable when anew nvgpu_mem comes in.
  o  Move CE suspend to after MM suspend.

JIRA NVGPU-30
JIRA NVGPU-138

Change-Id: Ie9286ae5a127c3fced86dfb9794e7d81eab0491c
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1574498
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>

1 files changed, 198 insertions, 17 deletions

diff --git a/drivers/gpu/nvgpu/common/mm/vidmem.c b/drivers/gpu/nvgpu/common/mm/vidmem.c
index d1c5a2e8..60b819d7 100644
--- a/drivers/gpu/nvgpu/common/mm/vidmem.c
+++ b/drivers/gpu/nvgpu/common/mm/vidmem.c
@@ -22,15 +22,55 @@
 
 #include <linux/scatterlist.h>
 
+#include <nvgpu/timers.h>
 #include <nvgpu/dma.h>
 #include <nvgpu/vidmem.h>
 #include <nvgpu/page_allocator.h>
+#include <nvgpu/enabled.h>
 
 #include "gk20a/gk20a.h"
 #include "gk20a/mm_gk20a.h"
 
+/*
+ * This is expected to be called from the shutdown path (or the error path in
+ * the vidmem init code). As such we do not expect new vidmem frees to be
+ * enqueued.
+ */
 void nvgpu_vidmem_destroy(struct gk20a *g)
 {
+        struct nvgpu_timeout timeout;
+
+        nvgpu_timeout_init(g, &timeout, 100, NVGPU_TIMER_RETRY_TIMER);
+
+        /*
+         * Ensure that the thread runs one last time to flush anything in the
+         * queue.
+         */
+        nvgpu_cond_signal_interruptible(&g->mm.vidmem.clearing_thread_cond);
+
+        /*
+         * Wait for at most 1 second before just continuing on. It doesn't make
+         * sense to hang the system over some potential memory leaks.
+         */
+        do {
+                bool empty;
+
+                nvgpu_mutex_acquire(&g->mm.vidmem.clear_list_mutex);
+                empty = nvgpu_list_empty(&g->mm.vidmem.clear_list_head);
+                nvgpu_mutex_release(&g->mm.vidmem.clear_list_mutex);
+
+                if (empty)
+                        break;
+
+                nvgpu_msleep(10);
+        } while (!nvgpu_timeout_expired(&timeout));
+
+        /*
+         * Kill the vidmem clearing thread now. This will wake the thread up
+         * automatically and cause the wait_interruptible condition trigger.
+         */
+        nvgpu_thread_stop(&g->mm.vidmem.clearing_thread);
+
         if (nvgpu_alloc_initialized(&g->mm.vidmem.allocator))
                 nvgpu_alloc_destroy(&g->mm.vidmem.allocator);
 }
@@ -107,6 +147,139 @@ static int __nvgpu_vidmem_do_clear_all(struct gk20a *g)
         return 0;
 }
 
+void nvgpu_vidmem_thread_pause_sync(struct mm_gk20a *mm)
+{
+        /*
+         * On the first increment of the pause_count (0 -> 1) take the pause
+         * lock and prevent the vidmem clearing thread from processing work
+         * items.
+         *
+         * Otherwise the increment is all that's needed - it's essentially a
+         * ref-count for the number of pause() calls.
+         *
+         * The sync component is implemented by waiting for the lock to be
+         * released by the clearing thread in case the thread is currently
+         * processing work items.
+         */
+        if (nvgpu_atomic_inc_return(&mm->vidmem.pause_count) == 1)
+                nvgpu_mutex_acquire(&mm->vidmem.clearing_thread_lock);
+}
+
+void nvgpu_vidmem_thread_unpause(struct mm_gk20a *mm)
+{
+        /*
+         * And on the last decrement (1 -> 0) release the pause lock and let
+         * the vidmem clearing thread continue.
+         */
+        if (nvgpu_atomic_dec_return(&mm->vidmem.pause_count) == 0)
+                nvgpu_mutex_release(&mm->vidmem.clearing_thread_lock);
+}
+
+int nvgpu_vidmem_clear_list_enqueue(struct gk20a *g, struct nvgpu_mem *mem)
+{
+        struct mm_gk20a *mm = &g->mm;
+
+        /*
+         * Crap. Can't enqueue new vidmem bufs! CE may be gone!
+         *
+         * However, an errant app can hold a vidmem dma_buf FD open past when
+         * the nvgpu driver has exited. Thus when the FD does get closed
+         * eventually the dma_buf release function will try to call the vidmem
+         * free function which will attempt to enqueue the vidmem into the
+         * vidmem clearing thread.
+         */
+        if (nvgpu_is_enabled(g, NVGPU_DRIVER_IS_DYING))
+                return -ENOSYS;
+
+        nvgpu_mutex_acquire(&mm->vidmem.clear_list_mutex);
+        nvgpu_list_add_tail(&mem->clear_list_entry,
+                            &mm->vidmem.clear_list_head);
+        nvgpu_atomic64_add(mem->aligned_size, &mm->vidmem.bytes_pending);
+        nvgpu_mutex_release(&mm->vidmem.clear_list_mutex);
+
+        nvgpu_cond_signal_interruptible(&mm->vidmem.clearing_thread_cond);
+
+        return 0;
+}
+
+static struct nvgpu_mem *nvgpu_vidmem_clear_list_dequeue(struct mm_gk20a *mm)
+{
+        struct nvgpu_mem *mem = NULL;
+
+        nvgpu_mutex_acquire(&mm->vidmem.clear_list_mutex);
+        if (!nvgpu_list_empty(&mm->vidmem.clear_list_head)) {
+                mem = nvgpu_list_first_entry(&mm->vidmem.clear_list_head,
+                                nvgpu_mem, clear_list_entry);
+                nvgpu_list_del(&mem->clear_list_entry);
+        }
+        nvgpu_mutex_release(&mm->vidmem.clear_list_mutex);
+
+        return mem;
+}
+
+static void nvgpu_vidmem_clear_pending_allocs(struct mm_gk20a *mm)
+{
+        struct gk20a *g = mm->g;
+        struct nvgpu_mem *mem;
+
+        while ((mem = nvgpu_vidmem_clear_list_dequeue(mm)) != NULL) {
+                nvgpu_vidmem_clear(g, mem);
+
+                WARN_ON(nvgpu_atomic64_sub_return(mem->aligned_size,
+                                        &g->mm.vidmem.bytes_pending) < 0);
+                mem->size = 0;
+                mem->aperture = APERTURE_INVALID;
+
+                __nvgpu_mem_free_vidmem_alloc(g, mem);
+                nvgpu_kfree(g, mem);
+        }
+}
+
+static int nvgpu_vidmem_clear_pending_allocs_thr(void *mm_ptr)
+{
+        struct mm_gk20a *mm = mm_ptr;
+
+        /*
+         * Simple thread who's sole job is to periodically clear userspace
+         * vidmem allocations that have been recently freed.
+         *
+         * Since it doesn't make sense to run unless there's pending work a
+         * condition field is used to wait for work. When the DMA API frees a
+         * userspace vidmem buf it enqueues it into the clear list and alerts us
+         * that we have some work to do.
+         */
+
+        while (!nvgpu_thread_should_stop(&mm->vidmem.clearing_thread)) {
+                int ret;
+
+                /*
+                 * Wait for work but also make sure we should not be paused.
+                 */
+                ret = NVGPU_COND_WAIT_INTERRUPTIBLE(
+                                &mm->vidmem.clearing_thread_cond,
+                                nvgpu_thread_should_stop(
+                                        &mm->vidmem.clearing_thread) ||
+                                !nvgpu_list_empty(&mm->vidmem.clear_list_head),
+                                0);
+                if (ret == -ERESTARTSYS)
+                        continue;
+
+                /*
+                 * Use this lock to implement a pause mechanism. By taking this
+                 * lock some other code can prevent this thread from processing
+                 * work items.
+                 */
+                if (!nvgpu_mutex_tryacquire(&mm->vidmem.clearing_thread_lock))
+                        continue;
+
+                nvgpu_vidmem_clear_pending_allocs(mm);
+
+                nvgpu_mutex_release(&mm->vidmem.clearing_thread_lock);
+        }
+
+        return 0;
+}
+
 int nvgpu_vidmem_init(struct mm_gk20a *mm)
 {
         struct gk20a *g = mm->g;
@@ -156,16 +329,39 @@ int nvgpu_vidmem_init(struct mm_gk20a *mm)
         mm->vidmem.bootstrap_base = bootstrap_base;
         mm->vidmem.bootstrap_size = bootstrap_size;
 
-        nvgpu_mutex_init(&mm->vidmem.first_clear_mutex);
+        err = nvgpu_cond_init(&mm->vidmem.clearing_thread_cond);
+        if (err)
+                goto fail;
 
-        INIT_WORK(&mm->vidmem.clear_mem_worker, nvgpu_vidmem_clear_mem_worker);
         nvgpu_atomic64_set(&mm->vidmem.bytes_pending, 0);
         nvgpu_init_list_node(&mm->vidmem.clear_list_head);
         nvgpu_mutex_init(&mm->vidmem.clear_list_mutex);
+        nvgpu_mutex_init(&mm->vidmem.clearing_thread_lock);
+        nvgpu_atomic_set(&mm->vidmem.pause_count, 0);
+
+        /*
+         * Start the thread off in the paused state. The thread doesn't have to
+         * be running for this to work. It will be woken up later on in
+         * finalize_poweron(). We won't necessarily have a CE context yet
+         * either, so hypothetically one could cause a race where we try to
+         * clear a vidmem struct before we have a CE context to do so.
+         */
+        nvgpu_vidmem_thread_pause_sync(mm);
+
+        err = nvgpu_thread_create(&mm->vidmem.clearing_thread, mm,
+                                  nvgpu_vidmem_clear_pending_allocs_thr,
+                                  "vidmem-clear");
+        if (err)
+                goto fail;
 
         gk20a_dbg_info("registered vidmem: %zu MB", size / SZ_1M);
 
         return 0;
+
+fail:
+        nvgpu_cond_destroy(&mm->vidmem.clearing_thread_cond);
+        nvgpu_vidmem_destroy(g);
+        return err;
 }
 
 int nvgpu_vidmem_get_space(struct gk20a *g, u64 *space)
@@ -244,21 +440,6 @@ int nvgpu_vidmem_clear(struct gk20a *g, struct nvgpu_mem *mem)
         return err;
 }
 
-struct nvgpu_mem *nvgpu_vidmem_get_pending_alloc(struct mm_gk20a *mm)
-{
-        struct nvgpu_mem *mem = NULL;
-
-        nvgpu_mutex_acquire(&mm->vidmem.clear_list_mutex);
-        if (!nvgpu_list_empty(&mm->vidmem.clear_list_head)) {
-                mem = nvgpu_list_first_entry(&mm->vidmem.clear_list_head,
-                                nvgpu_mem, clear_list_entry);
-                nvgpu_list_del(&mem->clear_list_entry);
-        }
-        nvgpu_mutex_release(&mm->vidmem.clear_list_mutex);
-
-        return mem;
-}
-
 static int nvgpu_vidmem_clear_all(struct gk20a *g)
 {
         int err;