Re: [PATCH][RFC] cpufreq: Avoid warning during resume by return EAGAIN if cpufreq is unavailable

[Rafael J. Wysocki]

On Monday, June 27, 2016 12:50:27 PM Viresh Kumar wrote:
> On 27-06-16, 03:12, Rafael J. Wysocki wrote:
> > ---
> >  drivers/cpufreq/cpufreq.c |7 ---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> > 
> > Index: linux-pm/drivers/cpufreq/cpufreq.c
> > ===
> > --- linux-pm.orig/drivers/cpufreq/cpufreq.c
> > +++ linux-pm/drivers/cpufreq/cpufreq.c
> > @@ -1544,9 +1544,6 @@ static unsigned int cpufreq_update_curre
> >  {
> > unsigned int new_freq;
> >  
> > -   if (cpufreq_suspended)
> > -   return 0;
> > -
> > new_freq = cpufreq_driver->get(policy->cpu);
> > if (!new_freq)
> > return 0;
> > @@ -2280,6 +2277,10 @@ int cpufreq_update_policy(unsigned int c
> >  * -> ask driver for current freq and notify governors about a change
> >  */
> > if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
> > +   if (cpufreq_suspended) {
> > +   ret = -EAGAIN;
> > +   goto unlock;
> > +   }
> > new_policy.cur = cpufreq_update_current_freq(policy);
> > if (WARN_ON(!new_policy.cur)) {
> > ret = -EIO;
> 
> Acked-by: Viresh Kumar 

Thanks, but this needs to go in in two pieces, because cpufreq_start_governor()
in the mainline doesn't check cpufreq_suspended (the linux-next version of it
does that).

So the second part of the patch is needed in the mainline/stable to get rid
of false-positive WARN_ON()s and the first one can go in on top of the
previous linux-next changes.

Thanks,
Rafael

Re: [PATCH][RFC] cpufreq: Avoid warning during resume by return EAGAIN if cpufreq is unavailable

[Rafael J. Wysocki]

On Monday, June 27, 2016 12:50:27 PM Viresh Kumar wrote:
> On 27-06-16, 03:12, Rafael J. Wysocki wrote:
> > ---
> >  drivers/cpufreq/cpufreq.c |7 ---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> > 
> > Index: linux-pm/drivers/cpufreq/cpufreq.c
> > ===
> > --- linux-pm.orig/drivers/cpufreq/cpufreq.c
> > +++ linux-pm/drivers/cpufreq/cpufreq.c
> > @@ -1544,9 +1544,6 @@ static unsigned int cpufreq_update_curre
> >  {
> > unsigned int new_freq;
> >  
> > -   if (cpufreq_suspended)
> > -   return 0;
> > -
> > new_freq = cpufreq_driver->get(policy->cpu);
> > if (!new_freq)
> > return 0;
> > @@ -2280,6 +2277,10 @@ int cpufreq_update_policy(unsigned int c
> >  * -> ask driver for current freq and notify governors about a change
> >  */
> > if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
> > +   if (cpufreq_suspended) {
> > +   ret = -EAGAIN;
> > +   goto unlock;
> > +   }
> > new_policy.cur = cpufreq_update_current_freq(policy);
> > if (WARN_ON(!new_policy.cur)) {
> > ret = -EIO;
> 
> Acked-by: Viresh Kumar 

Thanks, but this needs to go in in two pieces, because cpufreq_start_governor()
in the mainline doesn't check cpufreq_suspended (the linux-next version of it
does that).

So the second part of the patch is needed in the mainline/stable to get rid
of false-positive WARN_ON()s and the first one can go in on top of the
previous linux-next changes.

Thanks,
Rafael

Re: [PATCH][RFC] cpufreq: Avoid warning during resume by return EAGAIN if cpufreq is unavailable

[Viresh Kumar]

On 27-06-16, 03:12, Rafael J. Wysocki wrote:
> ---
>  drivers/cpufreq/cpufreq.c |7 ---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> Index: linux-pm/drivers/cpufreq/cpufreq.c
> ===
> --- linux-pm.orig/drivers/cpufreq/cpufreq.c
> +++ linux-pm/drivers/cpufreq/cpufreq.c
> @@ -1544,9 +1544,6 @@ static unsigned int cpufreq_update_curre
>  {
>   unsigned int new_freq;
>  
> - if (cpufreq_suspended)
> - return 0;
> -
>   new_freq = cpufreq_driver->get(policy->cpu);
>   if (!new_freq)
>   return 0;
> @@ -2280,6 +2277,10 @@ int cpufreq_update_policy(unsigned int c
>* -> ask driver for current freq and notify governors about a change
>*/
>   if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
> + if (cpufreq_suspended) {
> + ret = -EAGAIN;
> + goto unlock;
> + }
>   new_policy.cur = cpufreq_update_current_freq(policy);
>   if (WARN_ON(!new_policy.cur)) {
>   ret = -EIO;

Acked-by: Viresh Kumar 
-- 
viresh

Re: [PATCH][RFC] cpufreq: Avoid warning during resume by return EAGAIN if cpufreq is unavailable

[Viresh Kumar]

On 27-06-16, 03:12, Rafael J. Wysocki wrote:
> ---
>  drivers/cpufreq/cpufreq.c |7 ---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> Index: linux-pm/drivers/cpufreq/cpufreq.c
> ===
> --- linux-pm.orig/drivers/cpufreq/cpufreq.c
> +++ linux-pm/drivers/cpufreq/cpufreq.c
> @@ -1544,9 +1544,6 @@ static unsigned int cpufreq_update_curre
>  {
>   unsigned int new_freq;
>  
> - if (cpufreq_suspended)
> - return 0;
> -
>   new_freq = cpufreq_driver->get(policy->cpu);
>   if (!new_freq)
>   return 0;
> @@ -2280,6 +2277,10 @@ int cpufreq_update_policy(unsigned int c
>* -> ask driver for current freq and notify governors about a change
>*/
>   if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
> + if (cpufreq_suspended) {
> + ret = -EAGAIN;
> + goto unlock;
> + }
>   new_policy.cur = cpufreq_update_current_freq(policy);
>   if (WARN_ON(!new_policy.cur)) {
>   ret = -EIO;

Acked-by: Viresh Kumar 
-- 
viresh

Re: [PATCH][RFC] cpufreq: Avoid warning during resume by return EAGAIN if cpufreq is unavailable

[Rafael J. Wysocki]

On Sunday, June 26, 2016 12:28:48 AM Chen Yu wrote:
> Previously we saw warning during resume on some platforms,
> which use acpi-cpufreq:
> 
> smpboot: Booting Node 0 Processor 3 APIC 0x5
> cache: parent cpu3 should not be sleeping
> CPU3 is up
> ACPI: Waking up from system sleep state S3
> WARNING: CPU: 0 PID: 12546 at drivers/cpufreq/cpufreq.c:2173
> Call Trace:
> [] dump_stack+0x5c/0x77
> [] __warn+0xc4/0xe0
> [] cpufreq_update_policy+0xfe/0x150
> [] cpufreq_update_policy+0x150/0x150
> [] acpi_processor_notify+0x51/0xdc [processor]
> [] acpi_ev_notify_dispatch+0x3c/0x55
> [] acpi_os_execute_deferred+0x10/0x1a
> [] process_one_work+0x14b/0x400
> [] worker_thread+0x65/0x4a0
> [] rescuer_thread+0x340/0x340
> [] kthread+0xdf/0x100
> [] ret_from_fork+0x22/0x40
> [] kthread_park+0x50/0x50
> 
> This is because this platforms tries to notify
> the processor to reevaluate the _PPC object in _WAK,
> however at that time the cpufreq driver's resume has
> not been invoked yet, thus cpufreq_update_current_freq
> returns zero because of cpufreq_suspended = true, which
> caused the warning.
> 
> Actually it should be unnecessary to care the update request
> at that moment, so remove the warning and change the return
> value to -EAGAIN for invokers.
> 
> Reported-and-tested-by: BzukTuk 
> Signed-off-by: Chen Yu 
> ---
>  drivers/cpufreq/cpufreq.c | 7 +--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 9009295..67a3aa1 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2262,8 +2262,11 @@ int cpufreq_update_policy(unsigned int cpu)
>*/
>   if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
>   new_policy.cur = cpufreq_update_current_freq(policy);
> - if (WARN_ON(!new_policy.cur)) {
> - ret = -EIO;
> + if (!new_policy.cur) {
> + if (WARN_ON(!cpufreq_suspended))

If we know that cpufreq is suspended, there's no reason to call
cpufreq_update_current_freq() at all here.

> + ret = -EIO;
> + else
> + ret = -EAGAIN;
>   goto unlock;
>   }
>   }

Moreover, cpufreq_update_current_freq() has only two callers and the other
one already checks cpufreq_suspended before invoking it, so what about the
patch below instead?

---
 drivers/cpufreq/cpufreq.c |7 ---
 1 file changed, 4 insertions(+), 3 deletions(-)

Index: linux-pm/drivers/cpufreq/cpufreq.c
===
--- linux-pm.orig/drivers/cpufreq/cpufreq.c
+++ linux-pm/drivers/cpufreq/cpufreq.c
@@ -1544,9 +1544,6 @@ static unsigned int cpufreq_update_curre
 {
unsigned int new_freq;
 
-   if (cpufreq_suspended)
-   return 0;
-
new_freq = cpufreq_driver->get(policy->cpu);
if (!new_freq)
return 0;
@@ -2280,6 +2277,10 @@ int cpufreq_update_policy(unsigned int c
 * -> ask driver for current freq and notify governors about a change
 */
if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
+   if (cpufreq_suspended) {
+   ret = -EAGAIN;
+   goto unlock;
+   }
new_policy.cur = cpufreq_update_current_freq(policy);
if (WARN_ON(!new_policy.cur)) {
ret = -EIO;

Re: [PATCH][RFC] cpufreq: Avoid warning during resume by return EAGAIN if cpufreq is unavailable

[Rafael J. Wysocki]

On Sunday, June 26, 2016 12:28:48 AM Chen Yu wrote:
> Previously we saw warning during resume on some platforms,
> which use acpi-cpufreq:
> 
> smpboot: Booting Node 0 Processor 3 APIC 0x5
> cache: parent cpu3 should not be sleeping
> CPU3 is up
> ACPI: Waking up from system sleep state S3
> WARNING: CPU: 0 PID: 12546 at drivers/cpufreq/cpufreq.c:2173
> Call Trace:
> [] dump_stack+0x5c/0x77
> [] __warn+0xc4/0xe0
> [] cpufreq_update_policy+0xfe/0x150
> [] cpufreq_update_policy+0x150/0x150
> [] acpi_processor_notify+0x51/0xdc [processor]
> [] acpi_ev_notify_dispatch+0x3c/0x55
> [] acpi_os_execute_deferred+0x10/0x1a
> [] process_one_work+0x14b/0x400
> [] worker_thread+0x65/0x4a0
> [] rescuer_thread+0x340/0x340
> [] kthread+0xdf/0x100
> [] ret_from_fork+0x22/0x40
> [] kthread_park+0x50/0x50
> 
> This is because this platforms tries to notify
> the processor to reevaluate the _PPC object in _WAK,
> however at that time the cpufreq driver's resume has
> not been invoked yet, thus cpufreq_update_current_freq
> returns zero because of cpufreq_suspended = true, which
> caused the warning.
> 
> Actually it should be unnecessary to care the update request
> at that moment, so remove the warning and change the return
> value to -EAGAIN for invokers.
> 
> Reported-and-tested-by: BzukTuk 
> Signed-off-by: Chen Yu 
> ---
>  drivers/cpufreq/cpufreq.c | 7 +--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 9009295..67a3aa1 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2262,8 +2262,11 @@ int cpufreq_update_policy(unsigned int cpu)
>*/
>   if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
>   new_policy.cur = cpufreq_update_current_freq(policy);
> - if (WARN_ON(!new_policy.cur)) {
> - ret = -EIO;
> + if (!new_policy.cur) {
> + if (WARN_ON(!cpufreq_suspended))

If we know that cpufreq is suspended, there's no reason to call
cpufreq_update_current_freq() at all here.

> + ret = -EIO;
> + else
> + ret = -EAGAIN;
>   goto unlock;
>   }
>   }

Moreover, cpufreq_update_current_freq() has only two callers and the other
one already checks cpufreq_suspended before invoking it, so what about the
patch below instead?

---
 drivers/cpufreq/cpufreq.c |7 ---
 1 file changed, 4 insertions(+), 3 deletions(-)

Index: linux-pm/drivers/cpufreq/cpufreq.c
===
--- linux-pm.orig/drivers/cpufreq/cpufreq.c
+++ linux-pm/drivers/cpufreq/cpufreq.c
@@ -1544,9 +1544,6 @@ static unsigned int cpufreq_update_curre
 {
unsigned int new_freq;
 
-   if (cpufreq_suspended)
-   return 0;
-
new_freq = cpufreq_driver->get(policy->cpu);
if (!new_freq)
return 0;
@@ -2280,6 +2277,10 @@ int cpufreq_update_policy(unsigned int c
 * -> ask driver for current freq and notify governors about a change
 */
if (cpufreq_driver->get && !cpufreq_driver->setpolicy) {
+   if (cpufreq_suspended) {
+   ret = -EAGAIN;
+   goto unlock;
+   }
new_policy.cur = cpufreq_update_current_freq(policy);
if (WARN_ON(!new_policy.cur)) {
ret = -EIO;