V4L/DVB (7365): reduce stack usage of v4l1_compat_sync

poll_one allocated on stack struct poll_wqueues which is pretty big
structure (>500 bytes on x86_64). v4l1_compat_sync invokes poll_one
in a loop, so allocate struct poll_wqueues in v4l1_compat_sync (with
kmalloc) and pass it to poll_one.

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 8 insertions, 6 deletions

diff --git a/drivers/media/video/v4l1-compat.c b/drivers/media/video/v4l1-compat.c
index e42cea987964..a0f6c60279ec 100644
--- a/drivers/media/video/v4l1-compat.c
+++ b/drivers/media/video/v4l1-compat.c
@@ -199,14 +199,13 @@ pixelformat_to_palette(unsigned int pixelformat)
 
 /* ----------------------------------------------------------------- */
 
-static int poll_one(struct file *file)
+static int poll_one(struct file *file, struct poll_wqueues *pwq)
 {
         int retval = 1;
         poll_table *table;
-        struct poll_wqueues pwq; /*TODO: allocate dynamically*/
 
-        poll_initwait(&pwq);
-        table = &pwq.pt;
+        poll_initwait(pwq);
+        table = &pwq->pt;
         for (;;) {
                 int mask;
                 set_current_state(TASK_INTERRUPTIBLE);
@@ -221,7 +220,7 @@ static int poll_one(struct file *file)
                 schedule();
         }
         set_current_state(TASK_RUNNING);
-        poll_freewait(&pwq);
+        poll_freewait(pwq);
         return retval;
 }
 
@@ -1068,6 +1067,7 @@ static noinline int v4l1_compat_sync(
         int err;
         enum v4l2_buf_type captype = V4L2_BUF_TYPE_VIDEO_CAPTURE;
         struct v4l2_buffer buf;
+        struct poll_wqueues *pwq;
 
         memset(&buf, 0, sizeof(buf));
         buf.index = *i;
@@ -1091,10 +1091,11 @@ static noinline int v4l1_compat_sync(
                 goto done;
         }
 
+        pwq = kmalloc(sizeof(*pwq), GFP_KERNEL);
         /*  Loop as long as the buffer is queued, but not done  */
         while ((buf.flags & (V4L2_BUF_FLAG_QUEUED | V4L2_BUF_FLAG_DONE))
                                                 == V4L2_BUF_FLAG_QUEUED) {
-                err = poll_one(file);
+                err = poll_one(file, pwq);
                 if (err < 0 ||  /* error or sleep was interrupted  */
                     err == 0)   /* timeout? Shouldn't occur.  */
                         break;
@@ -1102,6 +1103,7 @@ static noinline int v4l1_compat_sync(
                 if (err < 0)
                         dprintk("VIDIOCSYNC / VIDIOC_QUERYBUF: %d\n", err);
         }
+        kfree(pwq);
         if (!(buf.flags & V4L2_BUF_FLAG_DONE)) /* not done */
                 goto done;
         do {