Re: [PATCH -next] media: cedrus: fix reference leak in cedrus_start_streaming

Re: [PATCH -next] media: cedrus: fix reference leak in cedrus_start_streaming

[Maxime Ripard]

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On Mon, Nov 02, 2020 at 10:26:22PM +0800, Zhang Qilong wrote:
> pm_runtime_get_sync will increment pm usage counter even it
> failed. Forgetting to pm_runtime_put_noidle will result in
> reference leak in cedrus_start_streaming. We should fix it.
> 
> Fixes: d5aecd289babf ("media: cedrus: Implement runtime PM")
> Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>

Shouldn't we fix pm_runtime_get_sync instead then? It seems that most of
the callers get this wrong, and that's definitely non-obvious.

Maxime

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[PATCH -next] media: cedrus: fix reference leak in cedrus_start_streaming

[Zhang Qilong]

pm_runtime_get_sync will increment pm usage counter even it
failed. Forgetting to pm_runtime_put_noidle will result in
reference leak in cedrus_start_streaming. We should fix it.

Fixes: d5aecd289babf ("media: cedrus: Implement runtime PM")
Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
---
 drivers/staging/media/sunxi/cedrus/cedrus_video.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_video.c b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
index 667b86dde1ee..911f607d9b09 100644
--- a/drivers/staging/media/sunxi/cedrus/cedrus_video.c
+++ b/drivers/staging/media/sunxi/cedrus/cedrus_video.c
@@ -479,8 +479,10 @@ static int cedrus_start_streaming(struct vb2_queue *vq, unsigned int count)
 
 	if (V4L2_TYPE_IS_OUTPUT(vq->type)) {
 		ret = pm_runtime_get_sync(dev->dev);
-		if (ret < 0)
+		if (ret < 0) {
+			pm_runtime_put_noidle(dev->dev);
 			goto err_cleanup;
+		}
 
 		if (dev->dec_ops[ctx->current_codec]->start) {
 			ret = dev->dec_ops[ctx->current_codec]->start(ctx);
-- 
2.17.1

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答复: [PATCH -next] media: cedrus: fix reference leak in cedrus_start_streaming

[zhangqilong]

Hi

> 
> On Mon, Nov 02, 2020 at 10:26:22PM +0800, Zhang Qilong wrote:
> > pm_runtime_get_sync will increment pm usage counter even it failed.
> > Forgetting to pm_runtime_put_noidle will result in reference leak in
> > cedrus_start_streaming. We should fix it.
> >
> > Fixes: d5aecd289babf ("media: cedrus: Implement runtime PM")
> > Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
> 
> Shouldn't we fix pm_runtime_get_sync instead then? It seems that most of the
> callers get this wrong, and that's definitely non-obvious.
>

 
I have ever thought to fix fix pm_runtime_get_sync, then I went to read the comment on this function, and found that this is what the author intended to do(comment: The possible return values of this function are the same as for pm_runtime_resume() and the runtime PM usage counter of @dev remains incremented in all cases, even if it returns an error code). On the other hand, I found that the number of callers that getting this right is much bigger than getting this wrong even many callers get wrong. So I submit server patches to fix them as I could.

Thanks, best wish!

Zhang Qilong
 
> Maxime
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Re: [PATCH -next] media: cedrus: fix reference leak in cedrus_start_streaming

[Dan Carpenter]

On Mon, Nov 02, 2020 at 03:18:38PM +0100, Maxime Ripard wrote:
> On Mon, Nov 02, 2020 at 10:26:22PM +0800, Zhang Qilong wrote:
> > pm_runtime_get_sync will increment pm usage counter even it
> > failed. Forgetting to pm_runtime_put_noidle will result in
> > reference leak in cedrus_start_streaming. We should fix it.
> > 
> > Fixes: d5aecd289babf ("media: cedrus: Implement runtime PM")
> > Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
> 
> Shouldn't we fix pm_runtime_get_sync instead then? It seems that most of
> the callers get this wrong, and that's definitely non-obvious.
> 
> Maxime

The other bug that people run into is that pm_runtime_get_sync() can
return 1 on success.

drivers/spi/spi-img-spfi.c:734 img_spfi_resume() warn: pm_runtime_get_sync() also returns 1 on success
drivers/mfd/arizona-core.c:49 arizona_clk32k_enable() warn: pm_runtime_get_sync() also returns 1 on success
drivers/usb/dwc3/dwc3-pci.c:212 dwc3_pci_resume_work() warn: pm_runtime_get_sync() also returns 1 on success
drivers/input/keyboard/omap4-keypad.c:279 omap4_keypad_probe() warn: pm_runtime_get_sync() also returns 1 on success
drivers/gpu/drm/vc4/vc4_dsi.c:839 vc4_dsi_encoder_enable() warn: pm_runtime_get_sync() also returns 1 on success
drivers/gpu/drm/i915/selftests/mock_gem_device.c:157 mock_gem_device() warn: 'pm_runtime_get_sync(&pdev->dev)' returns positive and negative
drivers/watchdog/rti_wdt.c:230 rti_wdt_probe() warn: pm_runtime_get_sync() also returns 1 on success
drivers/media/platform/exynos4-is/mipi-csis.c:513 s5pcsis_s_stream() warn: pm_runtime_get_sync() also returns 1 on success
drivers/media/platform/mtk-vcodec/mtk_vcodec_dec_pm.c:89 mtk_vcodec_dec_pw_on() warn: pm_runtime_get_sync() also returns 1 on success
drivers/media/platform/ti-vpe/cal.c:794 cal_probe() warn: pm_runtime_get_sync() also returns 1 on success
drivers/media/platform/ti-vpe/vpe.c:2478 vpe_runtime_get() warn: pm_runtime_get_sync() also returns 1 on success
drivers/media/i2c/smiapp/smiapp-core.c:1529 smiapp_pm_get_init() warn: pm_runtime_get_sync() also returns 1 on success

I don't really understand the point of incrementing the counter on
failure well enough to write a check for this...

regards,
dan carpenter
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Re: [PATCH -next] media: cedrus: fix reference leak in cedrus_start_streaming

[Hans Verkuil]

On 02/11/2020 15:18, Maxime Ripard wrote:
> On Mon, Nov 02, 2020 at 10:26:22PM +0800, Zhang Qilong wrote:
>> pm_runtime_get_sync will increment pm usage counter even it
>> failed. Forgetting to pm_runtime_put_noidle will result in
>> reference leak in cedrus_start_streaming. We should fix it.
>>
>> Fixes: d5aecd289babf ("media: cedrus: Implement runtime PM")
>> Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
> 
> Shouldn't we fix pm_runtime_get_sync instead then? It seems that most of
> the callers get this wrong, and that's definitely non-obvious.

It's been discussed before, but nobody stepped up to address this
issue. In the end I decided to just accept media patches that fix this
in the drivers rather than waiting for some mythical future core fix.

Nor do I think that you can just 'fix' pm_runtime_get_sync, since
then you will get cases where pm_runtime_put is called once too
often.

Regards,

	Hans

> 
> Maxime
> 

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答复: [PATCH -next] media: cedrus: fix reference leak in cedrus_start_streaming

[zhangqilong]

> On 02/11/2020 15:18, Maxime Ripard wrote:
> > On Mon, Nov 02, 2020 at 10:26:22PM +0800, Zhang Qilong wrote:
> >> pm_runtime_get_sync will increment pm usage counter even it failed.
> >> Forgetting to pm_runtime_put_noidle will result in reference leak in
> >> cedrus_start_streaming. We should fix it.
> >>
> >> Fixes: d5aecd289babf ("media: cedrus: Implement runtime PM")
> >> Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
> >
> > Shouldn't we fix pm_runtime_get_sync instead then? It seems that most
> > of the callers get this wrong, and that's definitely non-obvious.
> 
> It's been discussed before, but nobody stepped up to address this issue. In the
> end I decided to just accept media patches that fix this in the drivers rather
> than waiting for some mythical future core fix.
> 
> Nor do I think that you can just 'fix' pm_runtime_get_sync, since then you will
> get cases where pm_runtime_put is called once too often.
>

Thanks for your nice comment, if any updates occur about pm_runtime_get_sync, I will pay attention to it.

Thanks, best wish,
Zhang Qilong

> Regards,
> 
> 	Hans
> 
> >
> > Maxime
> >

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Re: [PATCH -next] media: cedrus: fix reference leak in cedrus_start_streaming

[Dan Carpenter]

On Wed, Nov 04, 2020 at 12:39:11PM +0100, Hans Verkuil wrote:
> On 02/11/2020 15:18, Maxime Ripard wrote:
> > On Mon, Nov 02, 2020 at 10:26:22PM +0800, Zhang Qilong wrote:
> >> pm_runtime_get_sync will increment pm usage counter even it
> >> failed. Forgetting to pm_runtime_put_noidle will result in
> >> reference leak in cedrus_start_streaming. We should fix it.
> >>
> >> Fixes: d5aecd289babf ("media: cedrus: Implement runtime PM")
> >> Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
> > 
> > Shouldn't we fix pm_runtime_get_sync instead then? It seems that most of
> > the callers get this wrong, and that's definitely non-obvious.
> 
> It's been discussed before, but nobody stepped up to address this
> issue. In the end I decided to just accept media patches that fix this
> in the drivers rather than waiting for some mythical future core fix.
> 
> Nor do I think that you can just 'fix' pm_runtime_get_sync, since
> then you will get cases where pm_runtime_put is called once too
> often.

Someone could easily add a helper function.  The only complication is
thinking of the correct name.

regards,
dan carpenter

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