[v1] locking/pvqspinlock: Correct the type of "old" variable in pv_kick_node()

[PATCH] locking/pvqspinlock: Correct the type of "old" variable in pv_kick_node()

Posted by Uros Bizjak 1 year, 4 months ago

"enum vcpu_state" is not compatible with "u8" type for all targets,
resulting in:

error: initialization of 'u8 *' {aka 'unsigned char *'} from incompatible pointer type 'enum vcpu_state *'

for LoongArch. Correct the type of "old" variable to "u8".

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Fixes: fea0e1820b51 ("locking/pvqspinlock: Use try_cmpxchg() in qspinlock_paravirt.h")
Reported-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Closes: https://lore.kernel.org/lkml/20240719024010.3296488-1-maobibo@loongson.cn/
---
 kernel/locking/qspinlock_paravirt.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
index f5a36e67b593..ac2e22502741 100644
--- a/kernel/locking/qspinlock_paravirt.h
+++ b/kernel/locking/qspinlock_paravirt.h
@@ -357,7 +357,7 @@ static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev)
 static void pv_kick_node(struct qspinlock *lock, struct mcs_spinlock *node)
 {
 	struct pv_node *pn = (struct pv_node *)node;
-	enum vcpu_state old = vcpu_halted;
+	u8 old = vcpu_halted;
 	/*
 	 * If the vCPU is indeed halted, advance its state to match that of
 	 * pv_wait_node(). If OTOH this fails, the vCPU was running and will
-- 
2.42.0

Re: [PATCH] locking/pvqspinlock: Correct the type of "old" variable in pv_kick_node()

Posted by maobibo 1 year, 4 months ago

Uros,

Sorry for late reply because of weekend time. This modification works 
well for me.

In later I want to define pv_node::state as int type on LoongArch 
because there is only int32/int64 cmpxchg is better supported on the 
system, however that is another issue.

Tested-by:Bibo Mao <maobibo@loongson.cn>

On 2024/7/22 上午12:45, Uros Bizjak wrote:
> "enum vcpu_state" is not compatible with "u8" type for all targets,
> resulting in:
> 
> error: initialization of 'u8 *' {aka 'unsigned char *'} from incompatible pointer type 'enum vcpu_state *'
> 
> for LoongArch. Correct the type of "old" variable to "u8".
> 
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Will Deacon <will@kernel.org>
> Cc: Waiman Long <longman@redhat.com>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> Fixes: fea0e1820b51 ("locking/pvqspinlock: Use try_cmpxchg() in qspinlock_paravirt.h")
> Reported-by: Bibo Mao <maobibo@loongson.cn>
> Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
> Closes: https://lore.kernel.org/lkml/20240719024010.3296488-1-maobibo@loongson.cn/
> ---
>   kernel/locking/qspinlock_paravirt.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
> index f5a36e67b593..ac2e22502741 100644
> --- a/kernel/locking/qspinlock_paravirt.h
> +++ b/kernel/locking/qspinlock_paravirt.h
> @@ -357,7 +357,7 @@ static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev)
>   static void pv_kick_node(struct qspinlock *lock, struct mcs_spinlock *node)
>   {
>   	struct pv_node *pn = (struct pv_node *)node;
> -	enum vcpu_state old = vcpu_halted;
> +	u8 old = vcpu_halted;
>   	/*
>   	 * If the vCPU is indeed halted, advance its state to match that of
>   	 * pv_wait_node(). If OTOH this fails, the vCPU was running and will
>

Re: [PATCH] locking/pvqspinlock: Correct the type of "old" variable in pv_kick_node()

Posted by Waiman Long 1 year, 4 months ago

On 7/22/24 02:54, maobibo wrote:
> Uros,
>
> Sorry for late reply because of weekend time. This modification works 
> well for me.
>
> In later I want to define pv_node::state as int type on LoongArch 
> because there is only int32/int64 cmpxchg is better supported on the 
> system, however that is another issue.

I thought about changing pv_node::state to int, but that requires 
changing the pv_wait() call to use int too. That doesn't work because 
pv_wait() is also used to monitor the state of the lock byte of the 
qspinlock. In essence, we can't use pvqspinlock if 8-bit cmpxchg isn't 
supported.

Cheers,
Longman

>
> Tested-by:Bibo Mao <maobibo@loongson.cn>
>
> On 2024/7/22 上午12:45, Uros Bizjak wrote:
>> "enum vcpu_state" is not compatible with "u8" type for all targets,
>> resulting in:
>>
>> error: initialization of 'u8 *' {aka 'unsigned char *'} from 
>> incompatible pointer type 'enum vcpu_state *'
>>
>> for LoongArch. Correct the type of "old" variable to "u8".
>>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> Cc: Ingo Molnar <mingo@kernel.org>
>> Cc: Will Deacon <will@kernel.org>
>> Cc: Waiman Long <longman@redhat.com>
>> Cc: Boqun Feng <boqun.feng@gmail.com>
>> Fixes: fea0e1820b51 ("locking/pvqspinlock: Use try_cmpxchg() in 
>> qspinlock_paravirt.h")
>> Reported-by: Bibo Mao <maobibo@loongson.cn>
>> Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
>> Closes: 
>> https://lore.kernel.org/lkml/20240719024010.3296488-1-maobibo@loongson.cn/
>> ---
>>   kernel/locking/qspinlock_paravirt.h | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/locking/qspinlock_paravirt.h 
>> b/kernel/locking/qspinlock_paravirt.h
>> index f5a36e67b593..ac2e22502741 100644
>> --- a/kernel/locking/qspinlock_paravirt.h
>> +++ b/kernel/locking/qspinlock_paravirt.h
>> @@ -357,7 +357,7 @@ static void pv_wait_node(struct mcs_spinlock 
>> *node, struct mcs_spinlock *prev)
>>   static void pv_kick_node(struct qspinlock *lock, struct 
>> mcs_spinlock *node)
>>   {
>>       struct pv_node *pn = (struct pv_node *)node;
>> -    enum vcpu_state old = vcpu_halted;
>> +    u8 old = vcpu_halted;
>>       /*
>>        * If the vCPU is indeed halted, advance its state to match 
>> that of
>>        * pv_wait_node(). If OTOH this fails, the vCPU was running and 
>> will
>>
>

Re: [PATCH] locking/pvqspinlock: Correct the type of "old" variable in pv_kick_node()

Posted by maobibo 1 year, 4 months ago


On 2024/7/22 下午11:13, Waiman Long wrote:
> 
> On 7/22/24 02:54, maobibo wrote:
>> Uros,
>>
>> Sorry for late reply because of weekend time. This modification works 
>> well for me.
>>
>> In later I want to define pv_node::state as int type on LoongArch 
>> because there is only int32/int64 cmpxchg is better supported on the 
>> system, however that is another issue.
> 
> I thought about changing pv_node::state to int, but that requires 
> changing the pv_wait() call to use int too. That doesn't work because 
> pv_wait() is also used to monitor the state of the lock byte of the 
> qspinlock. In essence, we can't use pvqspinlock if 8-bit cmpxchg isn't 
> supported.
Hi Longman,

yes, your are right. pv_wait also monitors the state of the qspinlock 
lock byte, so the parameter type about pv_wait must be u8.

LoongArch supports byte cmpxchg, only that word cmpxchg has higher 
efficiency. By the draft kernel compiling test, pvqspinlock can improve 
performance greatly when pCPU is shared by multiple vCPUs.

And thanks for your remaindering.

Regards
Bibo Mao
> 
> Cheers,
> Longman
> 
>>
>> Tested-by:Bibo Mao <maobibo@loongson.cn>
>>
>> On 2024/7/22 上午12:45, Uros Bizjak wrote:
>>> "enum vcpu_state" is not compatible with "u8" type for all targets,
>>> resulting in:
>>>
>>> error: initialization of 'u8 *' {aka 'unsigned char *'} from 
>>> incompatible pointer type 'enum vcpu_state *'
>>>
>>> for LoongArch. Correct the type of "old" variable to "u8".
>>>
>>> Cc: Peter Zijlstra <peterz@infradead.org>
>>> Cc: Ingo Molnar <mingo@kernel.org>
>>> Cc: Will Deacon <will@kernel.org>
>>> Cc: Waiman Long <longman@redhat.com>
>>> Cc: Boqun Feng <boqun.feng@gmail.com>
>>> Fixes: fea0e1820b51 ("locking/pvqspinlock: Use try_cmpxchg() in 
>>> qspinlock_paravirt.h")
>>> Reported-by: Bibo Mao <maobibo@loongson.cn>
>>> Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
>>> Closes: 
>>> https://lore.kernel.org/lkml/20240719024010.3296488-1-maobibo@loongson.cn/ 
>>>
>>> ---
>>>   kernel/locking/qspinlock_paravirt.h | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/kernel/locking/qspinlock_paravirt.h 
>>> b/kernel/locking/qspinlock_paravirt.h
>>> index f5a36e67b593..ac2e22502741 100644
>>> --- a/kernel/locking/qspinlock_paravirt.h
>>> +++ b/kernel/locking/qspinlock_paravirt.h
>>> @@ -357,7 +357,7 @@ static void pv_wait_node(struct mcs_spinlock 
>>> *node, struct mcs_spinlock *prev)
>>>   static void pv_kick_node(struct qspinlock *lock, struct 
>>> mcs_spinlock *node)
>>>   {
>>>       struct pv_node *pn = (struct pv_node *)node;
>>> -    enum vcpu_state old = vcpu_halted;
>>> +    u8 old = vcpu_halted;
>>>       /*
>>>        * If the vCPU is indeed halted, advance its state to match 
>>> that of
>>>        * pv_wait_node(). If OTOH this fails, the vCPU was running and 
>>> will
>>>
>>
>

Re: [PATCH] locking/pvqspinlock: Correct the type of "old" variable in pv_kick_node()

Posted by Waiman Long 1 year, 4 months ago

On 7/21/24 12:45, Uros Bizjak wrote:
> "enum vcpu_state" is not compatible with "u8" type for all targets,
> resulting in:
>
> error: initialization of 'u8 *' {aka 'unsigned char *'} from incompatible pointer type 'enum vcpu_state *'
>
> for LoongArch. Correct the type of "old" variable to "u8".
>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Will Deacon <will@kernel.org>
> Cc: Waiman Long <longman@redhat.com>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> Fixes: fea0e1820b51 ("locking/pvqspinlock: Use try_cmpxchg() in qspinlock_paravirt.h")
> Reported-by: Bibo Mao <maobibo@loongson.cn>
> Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
> Closes: https://lore.kernel.org/lkml/20240719024010.3296488-1-maobibo@loongson.cn/
> ---
>   kernel/locking/qspinlock_paravirt.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
> index f5a36e67b593..ac2e22502741 100644
> --- a/kernel/locking/qspinlock_paravirt.h
> +++ b/kernel/locking/qspinlock_paravirt.h
> @@ -357,7 +357,7 @@ static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev)
>   static void pv_kick_node(struct qspinlock *lock, struct mcs_spinlock *node)
>   {
>   	struct pv_node *pn = (struct pv_node *)node;
> -	enum vcpu_state old = vcpu_halted;
> +	u8 old = vcpu_halted;
>   	/*
>   	 * If the vCPU is indeed halted, advance its state to match that of
>   	 * pv_wait_node(). If OTOH this fails, the vCPU was running and will
Acked-by: Waiman Long <longman@redhat.com>

[tip: locking/urgent] locking/pvqspinlock: Correct the type of "old" variable in pv_kick_node()

Posted by tip-bot2 for Uros Bizjak 1 year, 4 months ago

The following commit has been merged into the locking/urgent branch of tip:

Commit-ID:     6623b0217d0c9bed80bfa43b778ce1c0eb03b497
Gitweb:        https://git.kernel.org/tip/6623b0217d0c9bed80bfa43b778ce1c0eb03b497
Author:        Uros Bizjak <ubizjak@gmail.com>
AuthorDate:    Sun, 21 Jul 2024 18:45:41 +02:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 29 Jul 2024 12:16:21 +02:00

locking/pvqspinlock: Correct the type of "old" variable in pv_kick_node()

"enum vcpu_state" is not compatible with "u8" type for all targets,
resulting in:

error: initialization of 'u8 *' {aka 'unsigned char *'} from incompatible pointer type 'enum vcpu_state *'

for LoongArch. Correct the type of "old" variable to "u8".

Fixes: fea0e1820b51 ("locking/pvqspinlock: Use try_cmpxchg() in qspinlock_paravirt.h")
Closes: https://lore.kernel.org/lkml/20240719024010.3296488-1-maobibo@loongson.cn/
Reported-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20240721164552.50175-1-ubizjak@gmail.com
---
 kernel/locking/qspinlock_paravirt.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h
index f5a36e6..ac2e225 100644
--- a/kernel/locking/qspinlock_paravirt.h
+++ b/kernel/locking/qspinlock_paravirt.h
@@ -357,7 +357,7 @@ static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev)
 static void pv_kick_node(struct qspinlock *lock, struct mcs_spinlock *node)
 {
 	struct pv_node *pn = (struct pv_node *)node;
-	enum vcpu_state old = vcpu_halted;
+	u8 old = vcpu_halted;
 	/*
 	 * If the vCPU is indeed halted, advance its state to match that of
 	 * pv_wait_node(). If OTOH this fails, the vCPU was running and will