From: Martin Karsten <mkarsten@uwaterloo.ca>
The napi_suspend_irqs routine bootstraps irq suspension by elongating
the defer timeout to irq_suspend_timeout.
The napi_resume_irqs routine effectly cancels irq suspension by forcing
the napi to be scheduled immediately.
Signed-off-by: Martin Karsten <mkarsten@uwaterloo.ca>
Co-developed-by: Joe Damato <jdamato@fastly.com>
Signed-off-by: Joe Damato <jdamato@fastly.com>
Tested-by: Joe Damato <jdamato@fastly.com>
Tested-by: Martin Karsten <mkarsten@uwaterloo.ca>
---
include/net/busy_poll.h | 3 +++
net/core/dev.c | 33 +++++++++++++++++++++++++++++++++
2 files changed, 36 insertions(+)
diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
index 9b09acac538e..f095b2bdeee1 100644
--- a/include/net/busy_poll.h
+++ b/include/net/busy_poll.h
@@ -52,6 +52,9 @@ void napi_busy_loop_rcu(unsigned int napi_id,
bool (*loop_end)(void *, unsigned long),
void *loop_end_arg, bool prefer_busy_poll, u16 budget);
+void napi_suspend_irqs(unsigned int napi_id);
+void napi_resume_irqs(unsigned int napi_id);
+
#else /* CONFIG_NET_RX_BUSY_POLL */
static inline unsigned long net_busy_loop_on(void)
{
diff --git a/net/core/dev.c b/net/core/dev.c
index 74060ba866d4..4de0dfc86e21 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6507,6 +6507,39 @@ void napi_busy_loop(unsigned int napi_id,
}
EXPORT_SYMBOL(napi_busy_loop);
+void napi_suspend_irqs(unsigned int napi_id)
+{
+ struct napi_struct *napi;
+
+ rcu_read_lock();
+ napi = napi_by_id(napi_id);
+ if (napi) {
+ unsigned long timeout = READ_ONCE(napi->dev->irq_suspend_timeout);
+
+ if (timeout)
+ hrtimer_start(&napi->timer, ns_to_ktime(timeout), HRTIMER_MODE_REL_PINNED);
+ }
+ rcu_read_unlock();
+}
+EXPORT_SYMBOL(napi_suspend_irqs);
+
+void napi_resume_irqs(unsigned int napi_id)
+{
+ struct napi_struct *napi;
+
+ rcu_read_lock();
+ napi = napi_by_id(napi_id);
+ if (napi) {
+ if (READ_ONCE(napi->dev->irq_suspend_timeout)) {
+ local_bh_disable();
+ napi_schedule(napi);
+ local_bh_enable();
+ }
+ }
+ rcu_read_unlock();
+}
+EXPORT_SYMBOL(napi_resume_irqs);
+
#endif /* CONFIG_NET_RX_BUSY_POLL */
static void napi_hash_add(struct napi_struct *napi)
--
2.25.1On Fri, Aug 23, 2024 at 7:31 PM Joe Damato <jdamato@fastly.com> wrote:
>
> From: Martin Karsten <mkarsten@uwaterloo.ca>
>
> The napi_suspend_irqs routine bootstraps irq suspension by elongating
> the defer timeout to irq_suspend_timeout.
>
> The napi_resume_irqs routine effectly cancels irq suspension by forcing
> the napi to be scheduled immediately.
>
> Signed-off-by: Martin Karsten <mkarsten@uwaterloo.ca>
> Co-developed-by: Joe Damato <jdamato@fastly.com>
> Signed-off-by: Joe Damato <jdamato@fastly.com>
> Tested-by: Joe Damato <jdamato@fastly.com>
> Tested-by: Martin Karsten <mkarsten@uwaterloo.ca>
> ---
> include/net/busy_poll.h | 3 +++
> net/core/dev.c | 33 +++++++++++++++++++++++++++++++++
> 2 files changed, 36 insertions(+)
>
> diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
> index 9b09acac538e..f095b2bdeee1 100644
> --- a/include/net/busy_poll.h
> +++ b/include/net/busy_poll.h
> @@ -52,6 +52,9 @@ void napi_busy_loop_rcu(unsigned int napi_id,
> bool (*loop_end)(void *, unsigned long),
> void *loop_end_arg, bool prefer_busy_poll, u16 budget);
>
> +void napi_suspend_irqs(unsigned int napi_id);
> +void napi_resume_irqs(unsigned int napi_id);
> +
> #else /* CONFIG_NET_RX_BUSY_POLL */
> static inline unsigned long net_busy_loop_on(void)
> {
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 74060ba866d4..4de0dfc86e21 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -6507,6 +6507,39 @@ void napi_busy_loop(unsigned int napi_id,
> }
> EXPORT_SYMBOL(napi_busy_loop);
>
> +void napi_suspend_irqs(unsigned int napi_id)
> +{
> + struct napi_struct *napi;
> +
> + rcu_read_lock();
> + napi = napi_by_id(napi_id);
> + if (napi) {
> + unsigned long timeout = READ_ONCE(napi->dev->irq_suspend_timeout);
> +
> + if (timeout)
> + hrtimer_start(&napi->timer, ns_to_ktime(timeout), HRTIMER_MODE_REL_PINNED);
> + }
> + rcu_read_unlock();
> +}
> +EXPORT_SYMBOL(napi_suspend_irqs);
> +
> +void napi_resume_irqs(unsigned int napi_id)
> +{
> + struct napi_struct *napi;
> +
> + rcu_read_lock();
> + napi = napi_by_id(napi_id);
> + if (napi) {
> + if (READ_ONCE(napi->dev->irq_suspend_timeout)) {
Since we'll read irq_suspend_timeout twice, we could have a situation
where the napi_schedule() will not be done
if another thread changes irq_suspend_timeout ?
If this is fine, a comment would be nice :)
The thing is that the kernel can not trust the user (think of syzbot)
> + local_bh_disable();
> + napi_schedule(napi);
> + local_bh_enable();
> + }
> + }
> + rcu_read_unlock();
> +}
> +EXPORT_SYMBOL(napi_resume_irqs);
> +
> #endif /* CONFIG_NET_RX_BUSY_POLL */
>
> static void napi_hash_add(struct napi_struct *napi)
> --
> 2.25.1
>
On 2024-08-23 14:14, Eric Dumazet wrote:
> On Fri, Aug 23, 2024 at 7:31 PM Joe Damato <jdamato@fastly.com> wrote:
>>
>> From: Martin Karsten <mkarsten@uwaterloo.ca>
>>
>> The napi_suspend_irqs routine bootstraps irq suspension by elongating
>> the defer timeout to irq_suspend_timeout.
>>
>> The napi_resume_irqs routine effectly cancels irq suspension by forcing
>> the napi to be scheduled immediately.
>>
>> Signed-off-by: Martin Karsten <mkarsten@uwaterloo.ca>
>> Co-developed-by: Joe Damato <jdamato@fastly.com>
>> Signed-off-by: Joe Damato <jdamato@fastly.com>
>> Tested-by: Joe Damato <jdamato@fastly.com>
>> Tested-by: Martin Karsten <mkarsten@uwaterloo.ca>
>> ---
>> include/net/busy_poll.h | 3 +++
>> net/core/dev.c | 33 +++++++++++++++++++++++++++++++++
>> 2 files changed, 36 insertions(+)
>>
>> diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
>> index 9b09acac538e..f095b2bdeee1 100644
>> --- a/include/net/busy_poll.h
>> +++ b/include/net/busy_poll.h
>> @@ -52,6 +52,9 @@ void napi_busy_loop_rcu(unsigned int napi_id,
>> bool (*loop_end)(void *, unsigned long),
>> void *loop_end_arg, bool prefer_busy_poll, u16 budget);
>>
>> +void napi_suspend_irqs(unsigned int napi_id);
>> +void napi_resume_irqs(unsigned int napi_id);
>> +
>> #else /* CONFIG_NET_RX_BUSY_POLL */
>> static inline unsigned long net_busy_loop_on(void)
>> {
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index 74060ba866d4..4de0dfc86e21 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -6507,6 +6507,39 @@ void napi_busy_loop(unsigned int napi_id,
>> }
>> EXPORT_SYMBOL(napi_busy_loop);
>>
>> +void napi_suspend_irqs(unsigned int napi_id)
>> +{
>> + struct napi_struct *napi;
>> +
>> + rcu_read_lock();
>> + napi = napi_by_id(napi_id);
>> + if (napi) {
>> + unsigned long timeout = READ_ONCE(napi->dev->irq_suspend_timeout);
>> +
>> + if (timeout)
>> + hrtimer_start(&napi->timer, ns_to_ktime(timeout), HRTIMER_MODE_REL_PINNED);
>> + }
>> + rcu_read_unlock();
>> +}
>> +EXPORT_SYMBOL(napi_suspend_irqs);
>> +
>> +void napi_resume_irqs(unsigned int napi_id)
>> +{
>> + struct napi_struct *napi;
>> +
>> + rcu_read_lock();
>> + napi = napi_by_id(napi_id);
>> + if (napi) {
>> + if (READ_ONCE(napi->dev->irq_suspend_timeout)) {
>
>
> Since we'll read irq_suspend_timeout twice, we could have a situation
> where the napi_schedule() will not be done
> if another thread changes irq_suspend_timeout ?
>
> If this is fine, a comment would be nice :)
>
> The thing is that the kernel can not trust the user (think of syzbot)
Yes, this should be fine. Calling napi_resume_irqs is done to restart
irq processing right away. In case irq_suspend_timeout is set to 0
between suspend and resume, the original value of irq_suspend_timeout
(when napi_suspend_irqs was called) determines the safety timeout as
intended and the watchdog will restart irq processing. We will a add
comment to make this clear.
Thanks,
Martin
On Fri, Aug 23, 2024 at 7:31 PM Joe Damato <jdamato@fastly.com> wrote: > > From: Martin Karsten <mkarsten@uwaterloo.ca> > > The napi_suspend_irqs routine bootstraps irq suspension by elongating > the defer timeout to irq_suspend_timeout. > > The napi_resume_irqs routine effectly cancels irq suspension by forcing > the napi to be scheduled immediately. > > Signed-off-by: Martin Karsten <mkarsten@uwaterloo.ca> > Co-developed-by: Joe Damato <jdamato@fastly.com> > Signed-off-by: Joe Damato <jdamato@fastly.com> > Tested-by: Joe Damato <jdamato@fastly.com> > Tested-by: Martin Karsten <mkarsten@uwaterloo.ca> > --- You have not CC me on all the patches in the series, making the review harder then necessary.
On Fri, Aug 23, 2024 at 07:56:32PM +0200, Eric Dumazet wrote: > On Fri, Aug 23, 2024 at 7:31 PM Joe Damato <jdamato@fastly.com> wrote: > > > > From: Martin Karsten <mkarsten@uwaterloo.ca> > > > > The napi_suspend_irqs routine bootstraps irq suspension by elongating > > the defer timeout to irq_suspend_timeout. > > > > The napi_resume_irqs routine effectly cancels irq suspension by forcing > > the napi to be scheduled immediately. > > > > Signed-off-by: Martin Karsten <mkarsten@uwaterloo.ca> > > Co-developed-by: Joe Damato <jdamato@fastly.com> > > Signed-off-by: Joe Damato <jdamato@fastly.com> > > Tested-by: Joe Damato <jdamato@fastly.com> > > Tested-by: Martin Karsten <mkarsten@uwaterloo.ca> > > --- > > You have not CC me on all the patches in the series, making the review > harder then necessary. My sincere apologies, Eric, and thank you for your time reviewing this. I used a script I'd been using for a while to generate the CC list, but it clearly has a bug. For any future revisions I will be sure to explicitly include you.
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