diff mbox series

[-next] PCI: Use GFP_ATOMIC in resource_alignment_store()

Message ID 20190831124932.18759-1-yuehaibing@huawei.com (mailing list archive)
State New, archived
Delegated to: Bjorn Helgaas
Headers show
Series [-next] PCI: Use GFP_ATOMIC in resource_alignment_store() | expand

Commit Message

Yue Haibing Aug. 31, 2019, 12:49 p.m. UTC 
When allocating memory, the GFP_KERNEL cannot be used during the
spin_lock period. It may cause scheduling when holding spin_lock.

Fixes: f13755318675 ("PCI: Move pci_[get|set]_resource_alignment_param() into their callers")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
---
 drivers/pci/pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Christoph Hellwig Sept. 2, 2019, 7:50 a.m. UTC | #1 
On Sat, Aug 31, 2019 at 12:49:32PM +0000, YueHaibing wrote:
> When allocating memory, the GFP_KERNEL cannot be used during the
> spin_lock period. It may cause scheduling when holding spin_lock.
> 
> Fixes: f13755318675 ("PCI: Move pci_[get|set]_resource_alignment_param() into their callers")
> Signed-off-by: YueHaibing <yuehaibing@huawei.com>
> ---
>  drivers/pci/pci.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 484e35349565..0b5fc6736f3f 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -6148,7 +6148,7 @@ static ssize_t resource_alignment_store(struct bus_type *bus,
>  	spin_lock(&resource_alignment_lock);
>  
>  	kfree(resource_alignment_param);
> -	resource_alignment_param = kstrndup(buf, count, GFP_KERNEL);
> +	resource_alignment_param = kstrndup(buf, count, GFP_ATOMIC);
>  
>  	spin_unlock(&resource_alignment_lock);

Why not move the allocation outside the lock? Something like this
seems much more sensible:


diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 484e35349565..fe205829f676 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6145,14 +6145,16 @@ static ssize_t resource_alignment_show(struct bus_type *bus, char *buf)
 static ssize_t resource_alignment_store(struct bus_type *bus,
 					const char *buf, size_t count)
 {
-	spin_lock(&resource_alignment_lock);
+	char *param = kstrndup(buf, count, GFP_KERNEL);
 
-	kfree(resource_alignment_param);
-	resource_alignment_param = kstrndup(buf, count, GFP_KERNEL);
+	if (!param)
+		return -ENOMEM;
 
+	spin_lock(&resource_alignment_lock);
+	kfree(resource_alignment_param);
+	resource_alignment_param = param;
 	spin_unlock(&resource_alignment_lock);
-
-	return resource_alignment_param ? count : -ENOMEM;
+	return count;
 }
 
 static BUS_ATTR_RW(resource_alignment);
Logan Gunthorpe Sept. 3, 2019, 3:51 p.m. UTC | #2 
On 2019-09-02 1:50 a.m., Christoph Hellwig wrote:
> On Sat, Aug 31, 2019 at 12:49:32PM +0000, YueHaibing wrote:
>> When allocating memory, the GFP_KERNEL cannot be used during the
>> spin_lock period. It may cause scheduling when holding spin_lock.
>>
>> Fixes: f13755318675 ("PCI: Move pci_[get|set]_resource_alignment_param() into their callers")
>> Signed-off-by: YueHaibing <yuehaibing@huawei.com>
>> ---
>>  drivers/pci/pci.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>> index 484e35349565..0b5fc6736f3f 100644
>> --- a/drivers/pci/pci.c
>> +++ b/drivers/pci/pci.c
>> @@ -6148,7 +6148,7 @@ static ssize_t resource_alignment_store(struct bus_type *bus,
>>  	spin_lock(&resource_alignment_lock);
>>  
>>  	kfree(resource_alignment_param);
>> -	resource_alignment_param = kstrndup(buf, count, GFP_KERNEL);
>> +	resource_alignment_param = kstrndup(buf, count, GFP_ATOMIC);
>>  
>>  	spin_unlock(&resource_alignment_lock);
> 
> Why not move the allocation outside the lock? Something like this
> seems much more sensible:

Yes, that seems like a good way to do it. Bjorn, can you squash
Christoph's patch or do you want me to resend a new one?

Thanks,

Logan

> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 484e35349565..fe205829f676 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -6145,14 +6145,16 @@ static ssize_t resource_alignment_show(struct bus_type *bus, char *buf)
>  static ssize_t resource_alignment_store(struct bus_type *bus,
>  					const char *buf, size_t count)
>  {
> -	spin_lock(&resource_alignment_lock);
> +	char *param = kstrndup(buf, count, GFP_KERNEL);
>  
> -	kfree(resource_alignment_param);
> -	resource_alignment_param = kstrndup(buf, count, GFP_KERNEL);
> +	if (!param)
> +		return -ENOMEM;
>  
> +	spin_lock(&resource_alignment_lock);
> +	kfree(resource_alignment_param);
> +	resource_alignment_param = param;
>  	spin_unlock(&resource_alignment_lock);
> -
> -	return resource_alignment_param ? count : -ENOMEM;
> +	return count;
>  }
>  
>  static BUS_ATTR_RW(resource_alignment);
>
Bjorn Helgaas Sept. 5, 2019, 9:47 p.m. UTC | #3 
On Tue, Sep 03, 2019 at 09:51:05AM -0600, Logan Gunthorpe wrote:
> 
> 
> On 2019-09-02 1:50 a.m., Christoph Hellwig wrote:
> > On Sat, Aug 31, 2019 at 12:49:32PM +0000, YueHaibing wrote:
> >> When allocating memory, the GFP_KERNEL cannot be used during the
> >> spin_lock period. It may cause scheduling when holding spin_lock.
> >>
> >> Fixes: f13755318675 ("PCI: Move pci_[get|set]_resource_alignment_param() into their callers")
> >> Signed-off-by: YueHaibing <yuehaibing@huawei.com>
> >> ---
> >>  drivers/pci/pci.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> >> index 484e35349565..0b5fc6736f3f 100644
> >> --- a/drivers/pci/pci.c
> >> +++ b/drivers/pci/pci.c
> >> @@ -6148,7 +6148,7 @@ static ssize_t resource_alignment_store(struct bus_type *bus,
> >>  	spin_lock(&resource_alignment_lock);
> >>  
> >>  	kfree(resource_alignment_param);
> >> -	resource_alignment_param = kstrndup(buf, count, GFP_KERNEL);
> >> +	resource_alignment_param = kstrndup(buf, count, GFP_ATOMIC);
> >>  
> >>  	spin_unlock(&resource_alignment_lock);
> > 
> > Why not move the allocation outside the lock? Something like this
> > seems much more sensible:
> 
> Yes, that seems like a good way to do it. Bjorn, can you squash
> Christoph's patch or do you want me to resend a new one?

I folded Christoph's fix into it, thanks!

> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index 484e35349565..fe205829f676 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -6145,14 +6145,16 @@ static ssize_t resource_alignment_show(struct bus_type *bus, char *buf)
> >  static ssize_t resource_alignment_store(struct bus_type *bus,
> >  					const char *buf, size_t count)
> >  {
> > -	spin_lock(&resource_alignment_lock);
> > +	char *param = kstrndup(buf, count, GFP_KERNEL);
> >  
> > -	kfree(resource_alignment_param);
> > -	resource_alignment_param = kstrndup(buf, count, GFP_KERNEL);
> > +	if (!param)
> > +		return -ENOMEM;
> >  
> > +	spin_lock(&resource_alignment_lock);
> > +	kfree(resource_alignment_param);
> > +	resource_alignment_param = param;
> >  	spin_unlock(&resource_alignment_lock);
> > -
> > -	return resource_alignment_param ? count : -ENOMEM;
> > +	return count;
> >  }
> >  
> >  static BUS_ATTR_RW(resource_alignment);
> >
diff mbox series

Patch

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 484e35349565..0b5fc6736f3f 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6148,7 +6148,7 @@  static ssize_t resource_alignment_store(struct bus_type *bus,
 	spin_lock(&resource_alignment_lock);
 
 	kfree(resource_alignment_param);
-	resource_alignment_param = kstrndup(buf, count, GFP_KERNEL);
+	resource_alignment_param = kstrndup(buf, count, GFP_ATOMIC);
 
 	spin_unlock(&resource_alignment_lock);