[PATCH v1] media: saa7146: Fix for "[BUG] process stuck when closing saa7146 [dvb_ttpci]"

From: Andrey Utkin
Date: Mon Oct 17 2016 - 14:28:10 EST

Release queued DMA buffers when ending streaming, so that
videobuf_waiton() doesn't block forever.

As reported, this fixes avoids occasional lockup of process reading from
video device, which manifests in such log:

INFO: task ffmpeg:9864 blocked for more than 120 seconds.
Tainted: P O 4.6.7 #3
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
ffmpeg D ffff880177cc7b00 0 9864 1 0x00000000
ffff880177cc7b00 0000000000000202 0000000000000202 ffffffff8180b4c0
ffff88019d79e4c0 ffffffff81064050 ffff880177cc7ae0 ffff880177cc8000
ffff880177cc7b18 ffff8801fd41d648 ffff8802307acca0 ffff8802307acc70
Call Trace:
[<ffffffff81064050>] ? preempt_count_add+0x89/0xab
[<ffffffff81477215>] schedule+0x86/0x9e
[<ffffffff81477215>] ? schedule+0x86/0x9e
[<ffffffffa0fe1c96>] videobuf_waiton+0x131/0x15e [videobuf_core]
[<ffffffff8107727b>] ? wait_woken+0x6d/0x6d
[<ffffffffa1017be9>] saa7146_dma_free+0x39/0x5b [saa7146_vv]
[<ffffffffa10186c4>] buffer_release+0x2a/0x3e [saa7146_vv]
[<ffffffffa0fee4a8>] videobuf_vm_close+0xd8/0x103 [videobuf_dma_sg]
[<ffffffff8112049e>] remove_vma+0x25/0x4d
[<ffffffff81121a32>] exit_mmap+0xce/0xf7
[<ffffffff8104381d>] mmput+0x4e/0xe2
[<ffffffff810491fd>] do_exit+0x372/0x920
[<ffffffff81049813>] do_group_exit+0x3c/0x98
[<ffffffff810522ef>] get_signal+0x4e8/0x56e
[<ffffffff810710a5>] ? task_dead_fair+0xd/0xf
[<ffffffff81017020>] do_signal+0x23/0x521
[<ffffffff81479e82>] ? _raw_spin_unlock_irqrestore+0x13/0x25
[<ffffffff8109710d>] ? hrtimer_try_to_cancel+0xd7/0x104
[<ffffffff8109b306>] ? ktime_get+0x4c/0xa1
[<ffffffff81096ea6>] ? update_rmtp+0x46/0x5b
[<ffffffff81097ce0>] ? hrtimer_nanosleep+0xe4/0x10e
[<ffffffff81096e3c>] ? hrtimer_init+0xeb/0xeb
[<ffffffff810014f8>] exit_to_usermode_loop+0x4f/0x93
[<ffffffff810019fe>] syscall_return_slowpath+0x3b/0x46
[<ffffffff8147a355>] entry_SYSCALL_64_fastpath+0x8d/0x8f

Reported-by: Philipp Matthias Hahn <pmhahn+video@xxxxxxxxx>
Tested-by: Philipp Matthias Hahn <pmhahn+video@xxxxxxxxx>
Signed-off-by: Andrey Utkin <andrey_utkin@xxxxxxxxxxxx>

Dear maintainers,
Please check whether the used buffer status (DONE) is correct for this
situation. I am in doubt, shouldn't it be VIDEOBUF_ERROR? However, ERROR
wasn't tested by Philipp and I guess it may indicate some undesired failure
status to application.

[PATCH v1] prefix is used to distinguish it from old letter with subj
"[PATCH] ..." which was a quick reply to Philipp's request and wasn't signed
off and otherwise properly formatted for submission.

drivers/media/common/saa7146/saa7146_video.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/media/common/saa7146/saa7146_video.c b/drivers/media/common/saa7146/saa7146_video.c
index ea2f3bf..e034bcf 100644
--- a/drivers/media/common/saa7146/saa7146_video.c
+++ b/drivers/media/common/saa7146/saa7146_video.c
@@ -390,6 +390,7 @@ static int video_end(struct saa7146_fh *fh, struct file *file)
struct saa7146_dev *dev = fh->dev;
struct saa7146_vv *vv = dev->vv_data;
+ struct saa7146_dmaqueue *q = &vv->video_dmaq;
struct saa7146_format *fmt = NULL;
unsigned long flags;
unsigned int resource;
@@ -428,6 +429,9 @@ static int video_end(struct saa7146_fh *fh, struct file *file)
/* shut down all used video dma transfers */
saa7146_write(dev, MC1, dmas);

+ if (q->curr)
+ saa7146_buffer_finish(dev, q, VIDEOBUF_DONE);
spin_unlock_irqrestore(&dev->slock, flags);

vv->video_fh = NULL;