RE: [EXT] [PATCH] media: amphion: Move the blocking check_is_responsed() out of wait event loop

[Ming Qian]

>From: Xiaolei Wang <xiaolei.wang@xxxxxxxxxxxxx>
>Sent: 2023年10月24日 13:27
>To: Ming Qian <ming.qian@xxxxxxx>; Eagle Zhou <eagle.zhou@xxxxxxx>;
>hverkuil-cisco@xxxxxxxxx; mchehab@xxxxxxxxxx
>Cc: linux-media@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
>Subject: [EXT] [PATCH] media: amphion: Move the blocking
>check_is_responsed() out of wait event loop
>
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>
>The blocking ops can't be used as a condition parameter of
>wait_event_timeout(), otherwise we would get a warning like below:
>
> do not call blocking ops when !TASK_RUNNING; state=2
> WARNING: CPU: 5 PID: 741 at kernel/sched/core.c:9859
>__might_sleep+0x80/0xa4
> CPU: 5 PID: 741 Comm: mxc_v4l2_vpu_te Tainted: G         C         6.1.55-yocto-
>standard #1
> Hardware name: Freescale i.MX8QM MEK (DT)
> pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)  pc :
>__might_sleep+0x80/0xa4  lr : __might_sleep+0x80/0xa4  sp : ffffffc0123738a0
> x29: ffffffc0123738a0 x28: ffffffc009194c48 x27: ffffffc00bbc1050
> x26: ffffff8814b282f0 x25: ffffff8814b280d0 x24: ffffff8814b28080
> x23: 0000000000000001 x22: 0000000000000032 x21: ffffffc00bbc1000
> x20: 000000000000011b x19: ffffffc009324670 x18: 00000000fffffffd
> x17: 30303c5b20746120 x16: 74657320323d6574 x15: 617473203b474e49
> x14: 00058b5b8b9aa1f1 x13: ffffffc00903cda0 x12: 00000000d744fcc9
> x11: 000000000000001c x10: 00000000000009a0 x9 : ffffffc0090201f4
> x8 : ffffff8828245000 x7 : 0000000000000001 x6 : 0000000000000001
> x5 : 00000000410fd080 x4 : 0000000000000002 x3 : ffffff8815aab4c8
> x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffff8828244600
>  Call trace:
>  __might_sleep+0x80/0xa4
>  mutex_lock+0x2c/0x80
>  sync_session_response+0x110/0x310
>  vpu_session_send_cmd+0x18c/0x244
>  vpu_session_start+0x38/0x70
>  vdec_start_session+0x1b4/0x3e0
>  vpu_vb2_start_streaming+0xa0/0x1c4
>  vb2_start_streaming+0x74/0x160
>  vb2_core_qbuf+0x488/0x650
>  vb2_qbuf+0x9c/0x100
>  v4l2_m2m_qbuf+0x7c/0x224
>  v4l2_m2m_ioctl_qbuf+0x20/0x2c
>  v4l_qbuf+0x50/0x6c
>  __video_do_ioctl+0x174/0x3f0
>  video_usercopy+0x210/0x7cc
>  video_ioctl2+0x20/0x30
>  v4l2_ioctl+0x48/0x6c
>
>It is not easy to convert the check_is_responsed() to a non-block function. In
>order to fix this issue, use a unwinding implementation of
>wait_event_timeout().

Hi Xiaolei,

    Thanks for your patch, this issue is caused by calling mutex_lock() in condition parameter of
wait_event_timeout(), I think we can fix this issue, then we can still use wait_event_timeout()
instead of rewrite it.

Ming

>
>Signed-off-by: Xiaolei Wang <xiaolei.wang@xxxxxxxxxxxxx>
>
>squash! media: amphion: Move the blocking check_is_responsed() out of wait
>event loop
>---
> drivers/media/platform/amphion/vpu_cmds.c | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/media/platform/amphion/vpu_cmds.c
>b/drivers/media/platform/amphion/vpu_cmds.c
>index c2337812573e..1abec8d9dad5 100644
>--- a/drivers/media/platform/amphion/vpu_cmds.c
>+++ b/drivers/media/platform/amphion/vpu_cmds.c
>@@ -271,6 +271,7 @@ static bool check_is_responsed(struct vpu_inst *inst,
>unsigned long key)  static int sync_session_response(struct vpu_inst *inst,
>unsigned long key, long timeout, int try)  {
>        struct vpu_core *core;
>+       struct wait_queue_entry wq_entry;
>
>        if (!inst || !inst->core)
>                return -EINVAL;
>@@ -278,7 +279,19 @@ static int sync_session_response(struct vpu_inst *inst,
>unsigned long key, long
>        core = inst->core;
>
>        call_void_vop(inst, wait_prepare);
>-       wait_event_timeout(core->ack_wq, check_is_responsed(inst, key),
>timeout);
>+       init_wait_entry(&wq_entry, 0);
>+       for (;;) {
>+               if (check_is_responsed(inst, key))
>+                       break;
>+
>+               prepare_to_wait_event(&core->ack_wq, &wq_entry,
>+ TASK_UNINTERRUPTIBLE);
>+
>+               timeout = schedule_timeout(timeout);
>+               if (!timeout)
>+                       break;
>+       }
>+
>+       finish_wait(&core->ack_wq, &wq_entry);
>        call_void_vop(inst, wait_finish);
>
>        if (!check_is_responsed(inst, key)) {
>--
>2.25.1