* [PATCH] hwrng: ks-sa - fix runtime pm imbalance on error
@ 2020-05-20 13:29 Dinghao Liu
2020-05-20 15:42 ` Sverdlin, Alexander (Nokia - DE/Ulm)
0 siblings, 1 reply; 7+ messages in thread
From: Dinghao Liu @ 2020-05-20 13:29 UTC (permalink / raw)
To: dinghao.liu, kjlu
Cc: Matt Mackall, Herbert Xu, Arnd Bergmann, Greg Kroah-Hartman,
Ben Dooks, Richard Fontana, Alexander Sverdlin, Allison Randal,
YueHaibing, Thomas Gleixner, linux-crypto, linux-kernel
pm_runtime_get_sync() increments the runtime PM usage counter even
the call returns an error code. Thus a pairing decrement is needed
on the error handling path to keep the counter balanced.
Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
---
drivers/char/hw_random/ks-sa-rng.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/char/hw_random/ks-sa-rng.c b/drivers/char/hw_random/ks-sa-rng.c
index e2330e757f1f..85c81da4a8af 100644
--- a/drivers/char/hw_random/ks-sa-rng.c
+++ b/drivers/char/hw_random/ks-sa-rng.c
@@ -244,6 +244,7 @@ static int ks_sa_rng_probe(struct platform_device *pdev)
ret = pm_runtime_get_sync(dev);
if (ret < 0) {
dev_err(dev, "Failed to enable SA power-domain\n");
+ pm_runtime_put_sync(dev);
pm_runtime_disable(dev);
return ret;
}
--
2.17.1
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH] hwrng: ks-sa - fix runtime pm imbalance on error
2020-05-20 13:29 [PATCH] hwrng: ks-sa - fix runtime pm imbalance on error Dinghao Liu
@ 2020-05-20 15:42 ` Sverdlin, Alexander (Nokia - DE/Ulm)
2020-05-20 16:45 ` stern
2020-05-21 6:21 ` dinghao.liu
0 siblings, 2 replies; 7+ messages in thread
From: Sverdlin, Alexander (Nokia - DE/Ulm) @ 2020-05-20 15:42 UTC (permalink / raw)
To: stern, dinghao.liu, kjlu
Cc: mpm, gregkh, herbert, ben.dooks, linux-kernel, arnd, allison,
yuehaibing, rfontana, linux-crypto, tglx
Hello Dinghao,
On Wed, 2020-05-20 at 21:29 +0800, Dinghao Liu wrote:
> pm_runtime_get_sync() increments the runtime PM usage counter even
> the call returns an error code. Thus a pairing decrement is needed
> on the error handling path to keep the counter balanced.
I believe, this is the wrong place for such kind of fix.
pm_runtime_get_sync() has obviously a broken semantics with regards to
your observation but no other driver does what you propose.
I think the proper fix belong into PM subsystem, please take a look
onto commit 15bcb91d7e60 "PM / Runtime: Implement autosuspend support".
> Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
> ---
> drivers/char/hw_random/ks-sa-rng.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/char/hw_random/ks-sa-rng.c b/drivers/char/hw_random/ks-sa-rng.c
> index e2330e757f1f..85c81da4a8af 100644
> --- a/drivers/char/hw_random/ks-sa-rng.c
> +++ b/drivers/char/hw_random/ks-sa-rng.c
> @@ -244,6 +244,7 @@ static int ks_sa_rng_probe(struct platform_device *pdev)
> ret = pm_runtime_get_sync(dev);
> if (ret < 0) {
> dev_err(dev, "Failed to enable SA power-domain\n");
> + pm_runtime_put_sync(dev);
> pm_runtime_disable(dev);
> return ret;
> }
--
Alexander Sverdlin.
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH] hwrng: ks-sa - fix runtime pm imbalance on error
2020-05-20 15:42 ` Sverdlin, Alexander (Nokia - DE/Ulm)
@ 2020-05-20 16:45 ` stern
2020-05-28 6:55 ` Herbert Xu
2020-05-21 6:21 ` dinghao.liu
1 sibling, 1 reply; 7+ messages in thread
From: stern @ 2020-05-20 16:45 UTC (permalink / raw)
To: Sverdlin, Alexander (Nokia - DE/Ulm)
Cc: dinghao.liu, kjlu, mpm, gregkh, herbert, ben.dooks, linux-kernel,
arnd, allison, yuehaibing, rfontana, linux-crypto, tglx
On Wed, May 20, 2020 at 03:42:17PM +0000, Sverdlin, Alexander (Nokia - DE/Ulm) wrote:
> Hello Dinghao,
>
> On Wed, 2020-05-20 at 21:29 +0800, Dinghao Liu wrote:
> > pm_runtime_get_sync() increments the runtime PM usage counter even
> > the call returns an error code. Thus a pairing decrement is needed
> > on the error handling path to keep the counter balanced.
>
> I believe, this is the wrong place for such kind of fix.
> pm_runtime_get_sync() has obviously a broken semantics with regards to
> your observation but no other driver does what you propose.
Look again. For example, see what usb_autoresume_device() in
drivers/usb/core/driver.c does.
You really shouldn't make generalizations such as "no other driver does
..." unless you have read the code for every driver in the kernel.
Alan Stern
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] hwrng: ks-sa - fix runtime pm imbalance on error
2020-05-20 16:45 ` stern
@ 2020-05-28 6:55 ` Herbert Xu
2020-05-28 7:13 ` dinghao.liu
2020-05-28 15:39 ` stern
0 siblings, 2 replies; 7+ messages in thread
From: Herbert Xu @ 2020-05-28 6:55 UTC (permalink / raw)
To: stern
Cc: Sverdlin, Alexander (Nokia - DE/Ulm),
dinghao.liu, kjlu, mpm, gregkh, ben.dooks, linux-kernel, arnd,
allison, yuehaibing, rfontana, linux-crypto, tglx,
Rafael J. Wysocki
On Wed, May 20, 2020 at 12:45:56PM -0400, stern@rowland.harvard.edu wrote:
> On Wed, May 20, 2020 at 03:42:17PM +0000, Sverdlin, Alexander (Nokia - DE/Ulm) wrote:
> > Hello Dinghao,
> >
> > On Wed, 2020-05-20 at 21:29 +0800, Dinghao Liu wrote:
> > > pm_runtime_get_sync() increments the runtime PM usage counter even
> > > the call returns an error code. Thus a pairing decrement is needed
> > > on the error handling path to keep the counter balanced.
> >
> > I believe, this is the wrong place for such kind of fix.
> > pm_runtime_get_sync() has obviously a broken semantics with regards to
> > your observation but no other driver does what you propose.
>
> Look again. For example, see what usb_autoresume_device() in
> drivers/usb/core/driver.c does.
However, there seems to be some disagreement as to what to do
when pm_runtime_get_sync fails. Your driver chooses to call
put_sync while others prefer pm_runtime_put_noidle (e.g., see
drivers/base/power/runtime.c).
This API does seem to be in a bit of a mess.
Cheers,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: Re: [PATCH] hwrng: ks-sa - fix runtime pm imbalance on error
2020-05-28 6:55 ` Herbert Xu
@ 2020-05-28 7:13 ` dinghao.liu
2020-05-28 15:39 ` stern
1 sibling, 0 replies; 7+ messages in thread
From: dinghao.liu @ 2020-05-28 7:13 UTC (permalink / raw)
To: Herbert Xu
Cc: stern, Sverdlin, Alexander (Nokia - DE/Ulm),
kjlu, mpm, gregkh, ben.dooks, linux-kernel, arnd, allison,
yuehaibing, rfontana, linux-crypto, tglx, Rafael J. Wysocki
> On Wed, May 20, 2020 at 12:45:56PM -0400, stern@rowland.harvard.edu wrote:
> > On Wed, May 20, 2020 at 03:42:17PM +0000, Sverdlin, Alexander (Nokia - DE/Ulm) wrote:
> > > Hello Dinghao,
> > >
> > > On Wed, 2020-05-20 at 21:29 +0800, Dinghao Liu wrote:
> > > > pm_runtime_get_sync() increments the runtime PM usage counter even
> > > > the call returns an error code. Thus a pairing decrement is needed
> > > > on the error handling path to keep the counter balanced.
> > >
> > > I believe, this is the wrong place for such kind of fix.
> > > pm_runtime_get_sync() has obviously a broken semantics with regards to
> > > your observation but no other driver does what you propose.
> >
> > Look again. For example, see what usb_autoresume_device() in
> > drivers/usb/core/driver.c does.
>
> However, there seems to be some disagreement as to what to do
> when pm_runtime_get_sync fails. Your driver chooses to call
> put_sync while others prefer pm_runtime_put_noidle (e.g., see
> drivers/base/power/runtime.c).
>
> This API does seem to be in a bit of a mess.
>
Here I think _put_noidle() is better. It's enough for this bug
and has no side effect (e.g., _put_sync may suspend the driver).
I will send a new patch for this bug.
Regards,
Dinghao
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] hwrng: ks-sa - fix runtime pm imbalance on error
2020-05-28 6:55 ` Herbert Xu
2020-05-28 7:13 ` dinghao.liu
@ 2020-05-28 15:39 ` stern
1 sibling, 0 replies; 7+ messages in thread
From: stern @ 2020-05-28 15:39 UTC (permalink / raw)
To: Herbert Xu
Cc: Sverdlin, Alexander (Nokia - DE/Ulm),
dinghao.liu, kjlu, mpm, gregkh, ben.dooks, linux-kernel, arnd,
allison, yuehaibing, rfontana, linux-crypto, tglx,
Rafael J. Wysocki
On Thu, May 28, 2020 at 04:55:19PM +1000, Herbert Xu wrote:
> On Wed, May 20, 2020 at 12:45:56PM -0400, stern@rowland.harvard.edu wrote:
> > On Wed, May 20, 2020 at 03:42:17PM +0000, Sverdlin, Alexander (Nokia - DE/Ulm) wrote:
> > > Hello Dinghao,
> > >
> > > On Wed, 2020-05-20 at 21:29 +0800, Dinghao Liu wrote:
> > > > pm_runtime_get_sync() increments the runtime PM usage counter even
> > > > the call returns an error code. Thus a pairing decrement is needed
> > > > on the error handling path to keep the counter balanced.
> > >
> > > I believe, this is the wrong place for such kind of fix.
> > > pm_runtime_get_sync() has obviously a broken semantics with regards to
> > > your observation but no other driver does what you propose.
> >
> > Look again. For example, see what usb_autoresume_device() in
> > drivers/usb/core/driver.c does.
>
> However, there seems to be some disagreement as to what to do
> when pm_runtime_get_sync fails. Your driver chooses to call
> put_sync while others prefer pm_runtime_put_noidle (e.g., see
> drivers/base/power/runtime.c).
It doesn't matter which function gets called; in these circumstances
(device still suspended or in an error state because a resume attempt
failed) they will do the same thing.
> This API does seem to be in a bit of a mess.
Suggestions and patches are welcome.
Alan Stern
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: Re: [PATCH] hwrng: ks-sa - fix runtime pm imbalance on error
2020-05-20 15:42 ` Sverdlin, Alexander (Nokia - DE/Ulm)
2020-05-20 16:45 ` stern
@ 2020-05-21 6:21 ` dinghao.liu
1 sibling, 0 replies; 7+ messages in thread
From: dinghao.liu @ 2020-05-21 6:21 UTC (permalink / raw)
To: Sverdlin, Alexander (Nokia - DE/Ulm)
Cc: stern, kjlu, mpm, gregkh, herbert, ben.dooks, linux-kernel, arnd,
allison, yuehaibing, rfontana, linux-crypto, tglx
Hi Alexander,
There are large amounts of cases that assume pm_runtime_get_sync()
will modify runtime PM usage counter on error. Fixing this in PM
subsystem will influence all callers of pm_runtime_get_sync() and
introduce new bugs. Therefore I think the better solution is to fix
misused cases individually.
Dinghao
> Hello Dinghao,
>
> On Wed, 2020-05-20 at 21:29 +0800, Dinghao Liu wrote:
> > pm_runtime_get_sync() increments the runtime PM usage counter even
> > the call returns an error code. Thus a pairing decrement is needed
> > on the error handling path to keep the counter balanced.
>
> I believe, this is the wrong place for such kind of fix.
> pm_runtime_get_sync() has obviously a broken semantics with regards to
> your observation but no other driver does what you propose.
> I think the proper fix belong into PM subsystem, please take a look
> onto commit 15bcb91d7e60 "PM / Runtime: Implement autosuspend support".
>
> > Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
> > ---
> > drivers/char/hw_random/ks-sa-rng.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/char/hw_random/ks-sa-rng.c b/drivers/char/hw_random/ks-sa-rng.c
> > index e2330e757f1f..85c81da4a8af 100644
> > --- a/drivers/char/hw_random/ks-sa-rng.c
> > +++ b/drivers/char/hw_random/ks-sa-rng.c
> > @@ -244,6 +244,7 @@ static int ks_sa_rng_probe(struct platform_device *pdev)
> > ret = pm_runtime_get_sync(dev);
> > if (ret < 0) {
> > dev_err(dev, "Failed to enable SA power-domain\n");
> > + pm_runtime_put_sync(dev);
> > pm_runtime_disable(dev);
> > return ret;
> > }
> --
> Alexander Sverdlin.
>
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2020-05-28 15:39 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2020-05-20 13:29 [PATCH] hwrng: ks-sa - fix runtime pm imbalance on error Dinghao Liu
2020-05-20 15:42 ` Sverdlin, Alexander (Nokia - DE/Ulm)
2020-05-20 16:45 ` stern
2020-05-28 6:55 ` Herbert Xu
2020-05-28 7:13 ` dinghao.liu
2020-05-28 15:39 ` stern
2020-05-21 6:21 ` dinghao.liu
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