t On Wed, 2010-02-03 at 20:53 +0100, John Kacur wrote:
> Balance local_irq_disable() and local_irq_enable() as well as
> spin_lock_irq() and spin_lock_unlock_irq
>
> Signed-off-by: John Kacur <[email protected]>
> ---
> mm/vmscan.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index c26986c..b895025 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1200,8 +1200,9 @@ static unsigned long shrink_inactive_list(unsigned long max_scan,
> if (current_is_kswapd())
> __count_vm_events(KSWAPD_STEAL, nr_freed);
> __count_zone_vm_events(PGSTEAL, zone, nr_freed);
> + local_irq_enable();
>
> - spin_lock(&zone->lru_lock);
> + spin_lock_irq(&zone->lru_lock);
> /*
> * Put back any unfreeable pages.
> */
The above looks wrong. I don't know the code, but just by looking at
where the locking and interrupts are, I can take a guess.
Lets add a little more of the code:
local_irq_disable();
if (current_is_kswapd())
__count_vm_events(KSWAPD_STEAL, nr_freed);
__count_zone_vm_events(PGSTEAL, zone, nr_freed);
spin_lock(&zone->lru_lock);
/*
I'm guessing the __count_zone_vm_events and friends need interrupts
disabled here, probably due to per cpu stuff. But if you enable
interrupts before the spin_lock() you may let an interrupt come in and
invalidate what was done above it.
So no, I do not think enabling interrupts here is a good thing.
-- Steve
On Wed, Feb 3, 2010 at 9:09 PM, Steven Rostedt <[email protected]> wrote:
> t On Wed, 2010-02-03 at 20:53 +0100, John Kacur wrote:
>> Balance local_irq_disable() and local_irq_enable() as well as
>> spin_lock_irq() and spin_lock_unlock_irq
>>
>> Signed-off-by: John Kacur <[email protected]>
>> ---
>> ?mm/vmscan.c | ? ?3 ++-
>> ?1 files changed, 2 insertions(+), 1 deletions(-)
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index c26986c..b895025 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -1200,8 +1200,9 @@ static unsigned long shrink_inactive_list(unsigned long max_scan,
>> ? ? ? ? ? ? ? if (current_is_kswapd())
>> ? ? ? ? ? ? ? ? ? ? ? __count_vm_events(KSWAPD_STEAL, nr_freed);
>> ? ? ? ? ? ? ? __count_zone_vm_events(PGSTEAL, zone, nr_freed);
>> + ? ? ? ? ? ? local_irq_enable();
>>
>> - ? ? ? ? ? ? spin_lock(&zone->lru_lock);
>> + ? ? ? ? ? ? spin_lock_irq(&zone->lru_lock);
>> ? ? ? ? ? ? ? /*
>> ? ? ? ? ? ? ? ?* Put back any unfreeable pages.
>> ? ? ? ? ? ? ? ?*/
>
>
> The above looks wrong. I don't know the code, but just by looking at
> where the locking and interrupts are, I can take a guess.
>
> Lets add a little more of the code:
>
> ? ? ? ? ? ? ? ?local_irq_disable();
> ? ? ? ? ? ? ? ?if (current_is_kswapd())
> ? ? ? ? ? ? ? ? ? ? ? ?__count_vm_events(KSWAPD_STEAL, nr_freed);
> ? ? ? ? ? ? ? ?__count_zone_vm_events(PGSTEAL, zone, nr_freed);
>
> ? ? ? ? ? ? ? ?spin_lock(&zone->lru_lock);
> ? ? ? ? ? ? ? ?/*
>
> I'm guessing the __count_zone_vm_events and friends need interrupts
> disabled here, probably due to per cpu stuff. But if you enable
> interrupts before the spin_lock() you may let an interrupt come in and
> invalidate what was done above it.
>
> So no, I do not think enabling interrupts here is a good thing.
>
okay, and since we have already done local_irq_disable(), then that is
why we only need the spin_lock() and not the spin_lock_irq() flavour?
> On Wed, Feb 3, 2010 at 9:09 PM, Steven Rostedt <[email protected]> wrote:
> > t On Wed, 2010-02-03 at 20:53 +0100, John Kacur wrote:
> >> Balance local_irq_disable() and local_irq_enable() as well as
> >> spin_lock_irq() and spin_lock_unlock_irq
> >>
> >> Signed-off-by: John Kacur <[email protected]>
> >> ---
> >> ?mm/vmscan.c | ? ?3 ++-
> >> ?1 files changed, 2 insertions(+), 1 deletions(-)
> >>
> >> diff --git a/mm/vmscan.c b/mm/vmscan.c
> >> index c26986c..b895025 100644
> >> --- a/mm/vmscan.c
> >> +++ b/mm/vmscan.c
> >> @@ -1200,8 +1200,9 @@ static unsigned long shrink_inactive_list(unsigned long max_scan,
> >> ? ? ? ? ? ? ? if (current_is_kswapd())
> >> ? ? ? ? ? ? ? ? ? ? ? __count_vm_events(KSWAPD_STEAL, nr_freed);
> >> ? ? ? ? ? ? ? __count_zone_vm_events(PGSTEAL, zone, nr_freed);
> >> + ? ? ? ? ? ? local_irq_enable();
> >>
> >> - ? ? ? ? ? ? spin_lock(&zone->lru_lock);
> >> + ? ? ? ? ? ? spin_lock_irq(&zone->lru_lock);
> >> ? ? ? ? ? ? ? /*
> >> ? ? ? ? ? ? ? ?* Put back any unfreeable pages.
> >> ? ? ? ? ? ? ? ?*/
> >
> >
> > The above looks wrong. I don't know the code, but just by looking at
> > where the locking and interrupts are, I can take a guess.
> >
> > Lets add a little more of the code:
> >
> > ? ? ? ? ? ? ? ?local_irq_disable();
> > ? ? ? ? ? ? ? ?if (current_is_kswapd())
> > ? ? ? ? ? ? ? ? ? ? ? ?__count_vm_events(KSWAPD_STEAL, nr_freed);
> > ? ? ? ? ? ? ? ?__count_zone_vm_events(PGSTEAL, zone, nr_freed);
> >
> > ? ? ? ? ? ? ? ?spin_lock(&zone->lru_lock);
> > ? ? ? ? ? ? ? ?/*
> >
> > I'm guessing the __count_zone_vm_events and friends need interrupts
> > disabled here, probably due to per cpu stuff. But if you enable
> > interrupts before the spin_lock() you may let an interrupt come in and
> > invalidate what was done above it.
> >
> > So no, I do not think enabling interrupts here is a good thing.
> >
>
> okay, and since we have already done local_irq_disable(), then that is
> why we only need the spin_lock() and not the spin_lock_irq() flavour?
Yes, spin_lock_irq() is equivalent to spin_lock() + irq_disable().
Now, we already disabled irq. then, we only need spin_lock().
So, I don't think shrink_inactive_list need any fix.
On Thu, Feb 4, 2010 at 1:22 AM, KOSAKI Motohiro
<[email protected]> wrote:
>> On Wed, Feb 3, 2010 at 9:09 PM, Steven Rostedt <[email protected]> wrote:
>> > t On Wed, 2010-02-03 at 20:53 +0100, John Kacur wrote:
>> >> Balance local_irq_disable() and local_irq_enable() as well as
>> >> spin_lock_irq() and spin_lock_unlock_irq
>> >>
>> >> Signed-off-by: John Kacur <[email protected]>
>> >> ---
>> >> ?mm/vmscan.c | ? ?3 ++-
>> >> ?1 files changed, 2 insertions(+), 1 deletions(-)
>> >>
>> >> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> >> index c26986c..b895025 100644
>> >> --- a/mm/vmscan.c
>> >> +++ b/mm/vmscan.c
>> >> @@ -1200,8 +1200,9 @@ static unsigned long shrink_inactive_list(unsigned long max_scan,
>> >> ? ? ? ? ? ? ? if (current_is_kswapd())
>> >> ? ? ? ? ? ? ? ? ? ? ? __count_vm_events(KSWAPD_STEAL, nr_freed);
>> >> ? ? ? ? ? ? ? __count_zone_vm_events(PGSTEAL, zone, nr_freed);
>> >> + ? ? ? ? ? ? local_irq_enable();
>> >>
>> >> - ? ? ? ? ? ? spin_lock(&zone->lru_lock);
>> >> + ? ? ? ? ? ? spin_lock_irq(&zone->lru_lock);
>> >> ? ? ? ? ? ? ? /*
>> >> ? ? ? ? ? ? ? ?* Put back any unfreeable pages.
>> >> ? ? ? ? ? ? ? ?*/
>> >
>> >
>> > The above looks wrong. I don't know the code, but just by looking at
>> > where the locking and interrupts are, I can take a guess.
>> >
>> > Lets add a little more of the code:
>> >
>> > ? ? ? ? ? ? ? ?local_irq_disable();
>> > ? ? ? ? ? ? ? ?if (current_is_kswapd())
>> > ? ? ? ? ? ? ? ? ? ? ? ?__count_vm_events(KSWAPD_STEAL, nr_freed);
>> > ? ? ? ? ? ? ? ?__count_zone_vm_events(PGSTEAL, zone, nr_freed);
>> >
>> > ? ? ? ? ? ? ? ?spin_lock(&zone->lru_lock);
>> > ? ? ? ? ? ? ? ?/*
>> >
>> > I'm guessing the __count_zone_vm_events and friends need interrupts
>> > disabled here, probably due to per cpu stuff. But if you enable
>> > interrupts before the spin_lock() you may let an interrupt come in and
>> > invalidate what was done above it.
>> >
>> > So no, I do not think enabling interrupts here is a good thing.
>> >
>>
>> okay, and since we have already done local_irq_disable(), then that is
>> why we only need the spin_lock() and not the spin_lock_irq() flavour?
>
> Yes, spin_lock_irq() is equivalent to spin_lock() + irq_disable().
> Now, we already disabled irq. then, we only need spin_lock().
>
> So, I don't think shrink_inactive_list need any fix.
>
Thanks for the explanation!