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* [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup
@ 2021-01-06  6:43 Matan Azrad
  2021-01-07 18:09 ` Maxime Coquelin
  0 siblings, 1 reply; 9+ messages in thread
From: Matan Azrad @ 2021-01-06  6:43 UTC (permalink / raw)
  To: dev; +Cc: Maxime Coquelin, stable

When the vDPA device is closed, the driver polling thread is canceled.
The polling thread locks the configuration mutex while it polls the CQs.

When the cancellation happens, it may terminate the thread inside the
critical section what remains the configuration mutex locked.

After device close, the driver may be configured again, in this case,
for example, when the first queue state is updated, the driver tries to
lock the mutex again and deadlock appears.

Initialize the mutex after the polling thread cancellation.

Fixes: 99abbd62c272 ("vdpa/mlx5: fix queue update synchronization")
Cc: stable@dpdk.org

Signed-off-by: Matan Azrad <matan@nvidia.com>
Acked-by: Xueming Li <xuemingl@nvidia.com>
---
 drivers/vdpa/mlx5/mlx5_vdpa.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/vdpa/mlx5/mlx5_vdpa.c b/drivers/vdpa/mlx5/mlx5_vdpa.c
index b64f364..0b2f1ab 100644
--- a/drivers/vdpa/mlx5/mlx5_vdpa.c
+++ b/drivers/vdpa/mlx5/mlx5_vdpa.c
@@ -295,6 +295,8 @@
 	}
 	priv->configured = 0;
 	priv->vid = 0;
+	/* The mutex may stay locked after event thread cancel - initiate it. */
+	pthread_mutex_init(&priv->vq_config_lock, NULL);
 	DRV_LOG(INFO, "vDPA device %d was closed.", vid);
 	return ret;
 }
-- 
1.8.3.1


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup
  2021-01-06  6:43 [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup Matan Azrad
@ 2021-01-07 18:09 ` Maxime Coquelin
  2021-01-08  8:48   ` David Marchand
  0 siblings, 1 reply; 9+ messages in thread
From: Maxime Coquelin @ 2021-01-07 18:09 UTC (permalink / raw)
  To: Matan Azrad, dev; +Cc: stable



On 1/6/21 7:43 AM, Matan Azrad wrote:
> When the vDPA device is closed, the driver polling thread is canceled.
> The polling thread locks the configuration mutex while it polls the CQs.
> 
> When the cancellation happens, it may terminate the thread inside the
> critical section what remains the configuration mutex locked.
> 
> After device close, the driver may be configured again, in this case,
> for example, when the first queue state is updated, the driver tries to
> lock the mutex again and deadlock appears.
> 
> Initialize the mutex after the polling thread cancellation.
> 
> Fixes: 99abbd62c272 ("vdpa/mlx5: fix queue update synchronization")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Matan Azrad <matan@nvidia.com>
> Acked-by: Xueming Li <xuemingl@nvidia.com>
> ---
>  drivers/vdpa/mlx5/mlx5_vdpa.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/vdpa/mlx5/mlx5_vdpa.c b/drivers/vdpa/mlx5/mlx5_vdpa.c
> index b64f364..0b2f1ab 100644
> --- a/drivers/vdpa/mlx5/mlx5_vdpa.c
> +++ b/drivers/vdpa/mlx5/mlx5_vdpa.c
> @@ -295,6 +295,8 @@
>  	}
>  	priv->configured = 0;
>  	priv->vid = 0;
> +	/* The mutex may stay locked after event thread cancel - initiate it. */
> +	pthread_mutex_init(&priv->vq_config_lock, NULL);
>  	DRV_LOG(INFO, "vDPA device %d was closed.", vid);
>  	return ret;
>  }
> 

I wonder if it would be possible and cleaner to disable cancellation on
the thread while the mutex is held?

Regards,
Maxime


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup
  2021-01-07 18:09 ` Maxime Coquelin
@ 2021-01-08  8:48   ` David Marchand
  2021-01-14  8:34     ` David Marchand
  0 siblings, 1 reply; 9+ messages in thread
From: David Marchand @ 2021-01-08  8:48 UTC (permalink / raw)
  To: Maxime Coquelin, Matan Azrad; +Cc: dev, dpdk stable

On Thu, Jan 7, 2021 at 7:09 PM Maxime Coquelin
<maxime.coquelin@redhat.com> wrote:
> On 1/6/21 7:43 AM, Matan Azrad wrote:
> > When the vDPA device is closed, the driver polling thread is canceled.
> > The polling thread locks the configuration mutex while it polls the CQs.
> >
> > When the cancellation happens, it may terminate the thread inside the
> > critical section what remains the configuration mutex locked.
> >
> > After device close, the driver may be configured again, in this case,
> > for example, when the first queue state is updated, the driver tries to
> > lock the mutex again and deadlock appears.
> >
> > Initialize the mutex after the polling thread cancellation.
> >
> > Fixes: 99abbd62c272 ("vdpa/mlx5: fix queue update synchronization")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Matan Azrad <matan@nvidia.com>
> > Acked-by: Xueming Li <xuemingl@nvidia.com>
> > ---
> >  drivers/vdpa/mlx5/mlx5_vdpa.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/vdpa/mlx5/mlx5_vdpa.c b/drivers/vdpa/mlx5/mlx5_vdpa.c
> > index b64f364..0b2f1ab 100644
> > --- a/drivers/vdpa/mlx5/mlx5_vdpa.c
> > +++ b/drivers/vdpa/mlx5/mlx5_vdpa.c
> > @@ -295,6 +295,8 @@
> >       }
> >       priv->configured = 0;
> >       priv->vid = 0;
> > +     /* The mutex may stay locked after event thread cancel - initiate it. */
> > +     pthread_mutex_init(&priv->vq_config_lock, NULL);
> >       DRV_LOG(INFO, "vDPA device %d was closed.", vid);
> >       return ret;
> >  }
> >
>
> I wonder if it would be possible and cleaner to disable cancellation on
> the thread while the mutex is held?

+1

-- 
David Marchand


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup
  2021-01-08  8:48   ` David Marchand
@ 2021-01-14  8:34     ` David Marchand
  2021-01-14 11:49       ` Matan Azrad
  0 siblings, 1 reply; 9+ messages in thread
From: David Marchand @ 2021-01-14  8:34 UTC (permalink / raw)
  To: Maxime Coquelin, Matan Azrad; +Cc: dev, dpdk stable

On Fri, Jan 8, 2021 at 9:48 AM David Marchand <david.marchand@redhat.com> wrote:
> > I wonder if it would be possible and cleaner to disable cancellation on
> > the thread while the mutex is held?
>
> +1

IEEE Std 1003.1-2001/Cor 2-2004, item XBD/TC2/D6/26 is applied, adding
pthread_t to the list of types that are not required to be arithmetic
types, thus allowing pthread_t to be defined as a structure.

It would be better to leave pthread_t alone and not interpret it:

if (priv->timer_tid) {
    pthread_cancel(priv->timer_tid);
    pthread_join(priv->timer_tid, &status);
}
priv->timer_tid = 0;


-- 
David Marchand


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup
  2021-01-14  8:34     ` David Marchand
@ 2021-01-14 11:49       ` Matan Azrad
  2021-01-14 12:38         ` Maxime Coquelin
  0 siblings, 1 reply; 9+ messages in thread
From: Matan Azrad @ 2021-01-14 11:49 UTC (permalink / raw)
  To: David Marchand, Maxime Coquelin; +Cc: dev, dpdk stable

Hi Maxime and David

Thank you for Review.

From: David Marchand
> On Fri, Jan 8, 2021 at 9:48 AM David Marchand
> <david.marchand@redhat.com> wrote:
> > > I wonder if it would be possible and cleaner to disable cancellation
> > > on the thread while the mutex is held?

Yes, we can cause thread to return by some global variable sync.
It is the same logic.

> > +1
> 
> IEEE Std 1003.1-2001/Cor 2-2004, item XBD/TC2/D6/26 is applied, adding
> pthread_t to the list of types that are not required to be arithmetic types, thus
> allowing pthread_t to be defined as a structure.
> 
> It would be better to leave pthread_t alone and not interpret it:
> 
> if (priv->timer_tid) {
>     pthread_cancel(priv->timer_tid);
>     pthread_join(priv->timer_tid, &status); }
> priv->timer_tid = 0;


I'm not sure why you think it is better in this specific case.
The cancellation will close the thread in faster way, no need to wait for the thread to close itself.


> 
> --
> David Marchand


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup
  2021-01-14 11:49       ` Matan Azrad
@ 2021-01-14 12:38         ` Maxime Coquelin
  2021-01-14 13:09           ` Matan Azrad
  0 siblings, 1 reply; 9+ messages in thread
From: Maxime Coquelin @ 2021-01-14 12:38 UTC (permalink / raw)
  To: Matan Azrad, David Marchand; +Cc: dev, dpdk stable

Hi Matan,

On 1/14/21 12:49 PM, Matan Azrad wrote:
> Hi Maxime and David
> 
> Thank you for Review.
> 
> From: David Marchand
>> On Fri, Jan 8, 2021 at 9:48 AM David Marchand
>> <david.marchand@redhat.com> wrote:
>>>> I wonder if it would be possible and cleaner to disable cancellation
>>>> on the thread while the mutex is held?
> 
> Yes, we can cause thread to return by some global variable sync.
> It is the same logic.

No, that was not my suggestion. My suggestion is to block the thread
cancellation while in the critical section, using
pthread_setcancelstate().


>>> +1
>>
>> IEEE Std 1003.1-2001/Cor 2-2004, item XBD/TC2/D6/26 is applied, adding
>> pthread_t to the list of types that are not required to be arithmetic types, thus
>> allowing pthread_t to be defined as a structure.
>>
>> It would be better to leave pthread_t alone and not interpret it:
>>
>> if (priv->timer_tid) {
>>     pthread_cancel(priv->timer_tid);
>>     pthread_join(priv->timer_tid, &status); }
>> priv->timer_tid = 0;
> 
> 
> I'm not sure why you think it is better in this specific case.
> The cancellation will close the thread in faster way, no need to wait for the thread to close itself.
> 
> 
>>
>> --
>> David Marchand
> 


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup
  2021-01-14 12:38         ` Maxime Coquelin
@ 2021-01-14 13:09           ` Matan Azrad
  2021-01-14 14:27             ` Maxime Coquelin
  0 siblings, 1 reply; 9+ messages in thread
From: Matan Azrad @ 2021-01-14 13:09 UTC (permalink / raw)
  To: Maxime Coquelin, David Marchand; +Cc: dev, dpdk stable



From: Maxime Coquelin
> Hi Matan,
> 
> On 1/14/21 12:49 PM, Matan Azrad wrote:
> > Hi Maxime and David
> >
> > Thank you for Review.
> >
> > From: David Marchand
> >> On Fri, Jan 8, 2021 at 9:48 AM David Marchand
> >> <david.marchand@redhat.com> wrote:
> >>>> I wonder if it would be possible and cleaner to disable
> >>>> cancellation on the thread while the mutex is held?
> >
> > Yes, we can cause thread to return by some global variable sync.
> > It is the same logic.
> 
> No, that was not my suggestion. My suggestion is to block the thread
> cancellation while in the critical section, using pthread_setcancelstate().

Yes, Generally it is better to let the thread control his cancellation, either cancel itself or enabling\disabling cancellations. 

I don't see a reason to wait for the thread in current logic - the critical section is not important to be completed here.

We just want to close the thread and to clean the mutex. 
 
> >>> +1
> >>
> >> IEEE Std 1003.1-2001/Cor 2-2004, item XBD/TC2/D6/26 is applied,
> >> adding pthread_t to the list of types that are not required to be
> >> arithmetic types, thus allowing pthread_t to be defined as a structure.
> >>
> >> It would be better to leave pthread_t alone and not interpret it:
> >>
> >> if (priv->timer_tid) {
> >>     pthread_cancel(priv->timer_tid);
> >>     pthread_join(priv->timer_tid, &status); }
> >> priv->timer_tid = 0;
> >
> >
> > I'm not sure why you think it is better in this specific case.
> > The cancellation will close the thread in faster way, no need to wait for the
> thread to close itself.
> >
> >
> >>
> >> --
> >> David Marchand
> >


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup
  2021-01-14 13:09           ` Matan Azrad
@ 2021-01-14 14:27             ` Maxime Coquelin
  2021-01-14 15:23               ` Matan Azrad
  0 siblings, 1 reply; 9+ messages in thread
From: Maxime Coquelin @ 2021-01-14 14:27 UTC (permalink / raw)
  To: Matan Azrad, David Marchand; +Cc: dev, dpdk stable



On 1/14/21 2:09 PM, Matan Azrad wrote:
> 
> 
> From: Maxime Coquelin
>> Hi Matan,
>>
>> On 1/14/21 12:49 PM, Matan Azrad wrote:
>>> Hi Maxime and David
>>>
>>> Thank you for Review.
>>>
>>> From: David Marchand
>>>> On Fri, Jan 8, 2021 at 9:48 AM David Marchand
>>>> <david.marchand@redhat.com> wrote:
>>>>>> I wonder if it would be possible and cleaner to disable
>>>>>> cancellation on the thread while the mutex is held?
>>>
>>> Yes, we can cause thread to return by some global variable sync.
>>> It is the same logic.
>>
>> No, that was not my suggestion. My suggestion is to block the thread
>> cancellation while in the critical section, using pthread_setcancelstate().
> 
> Yes, Generally it is better to let the thread control his cancellation, either cancel itself or enabling\disabling cancellations. 
> 
> I don't see a reason to wait for the thread in current logic - the critical section is not important to be completed here.

The reason I see is there are quite a few things done in this critical
section. And if tomorrow someone add new things in it, he may not know
the thread can be cancelled at any time, which could cause hard to debug
issues.

> We just want to close the thread and to clean the mutex. 
>  
>>>>> +1
>>>>
>>>> IEEE Std 1003.1-2001/Cor 2-2004, item XBD/TC2/D6/26 is applied,
>>>> adding pthread_t to the list of types that are not required to be
>>>> arithmetic types, thus allowing pthread_t to be defined as a structure.
>>>>
>>>> It would be better to leave pthread_t alone and not interpret it:
>>>>
>>>> if (priv->timer_tid) {
>>>>     pthread_cancel(priv->timer_tid);
>>>>     pthread_join(priv->timer_tid, &status); }
>>>> priv->timer_tid = 0;
>>>
>>>
>>> I'm not sure why you think it is better in this specific case.
>>> The cancellation will close the thread in faster way, no need to wait for the
>> thread to close itself.
>>>
>>>
>>>>
>>>> --
>>>> David Marchand
>>>
> 


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup
  2021-01-14 14:27             ` Maxime Coquelin
@ 2021-01-14 15:23               ` Matan Azrad
  0 siblings, 0 replies; 9+ messages in thread
From: Matan Azrad @ 2021-01-14 15:23 UTC (permalink / raw)
  To: Maxime Coquelin, David Marchand; +Cc: dev, dpdk stable



From: Maxime Coquelin
> On 1/14/21 2:09 PM, Matan Azrad wrote:
> >
> >
> > From: Maxime Coquelin
> >> Hi Matan,
> >>
> >> On 1/14/21 12:49 PM, Matan Azrad wrote:
> >>> Hi Maxime and David
> >>>
> >>> Thank you for Review.
> >>>
> >>> From: David Marchand
> >>>> On Fri, Jan 8, 2021 at 9:48 AM David Marchand
> >>>> <david.marchand@redhat.com> wrote:
> >>>>>> I wonder if it would be possible and cleaner to disable
> >>>>>> cancellation on the thread while the mutex is held?
> >>>
> >>> Yes, we can cause thread to return by some global variable sync.
> >>> It is the same logic.
> >>
> >> No, that was not my suggestion. My suggestion is to block the thread
> >> cancellation while in the critical section, using pthread_setcancelstate().
> >
> > Yes, Generally it is better to let the thread control his cancellation, either
> cancel itself or enabling\disabling cancellations.
> >
> > I don't see a reason to wait for the thread in current logic - the critical section
> is not important to be completed here.
> 
> The reason I see is there are quite a few things done in this critical section. And
> if tomorrow someone add new things in it, he may not know the thread can be
> cancelled at any time, which could cause hard to debug issues.

As I said, here it is not needed, this thread designed just to cause guest notifications.

The optional future developer mistake can be done also outside the critical section in in any other place - we cannot protect it.

The design choice is to close the thread fast.

> > We just want to close the thread and to clean the mutex.
> >
> >>>>> +1
> >>>>
> >>>> IEEE Std 1003.1-2001/Cor 2-2004, item XBD/TC2/D6/26 is applied,
> >>>> adding pthread_t to the list of types that are not required to be
> >>>> arithmetic types, thus allowing pthread_t to be defined as a structure.
> >>>>
> >>>> It would be better to leave pthread_t alone and not interpret it:
> >>>>
> >>>> if (priv->timer_tid) {
> >>>>     pthread_cancel(priv->timer_tid);
> >>>>     pthread_join(priv->timer_tid, &status); }
> >>>> priv->timer_tid = 0;
> >>>
> >>>
> >>> I'm not sure why you think it is better in this specific case.
> >>> The cancellation will close the thread in faster way, no need to
> >>> wait for the
> >> thread to close itself.
> >>>
> >>>
> >>>>
> >>>> --
> >>>> David Marchand
> >>>
> >


^ permalink raw reply	[flat|nested] 9+ messages in thread

end of thread, other threads:[~2021-01-14 15:23 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-01-06  6:43 [dpdk-stable] [PATCH] vdpa/mlx5: fix configuration mutex cleanup Matan Azrad
2021-01-07 18:09 ` Maxime Coquelin
2021-01-08  8:48   ` David Marchand
2021-01-14  8:34     ` David Marchand
2021-01-14 11:49       ` Matan Azrad
2021-01-14 12:38         ` Maxime Coquelin
2021-01-14 13:09           ` Matan Azrad
2021-01-14 14:27             ` Maxime Coquelin
2021-01-14 15:23               ` Matan Azrad

patches for DPDK stable branches

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	# If you have public-inbox 1.1+ installed, you may
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