dev->poll_limit_ns could be zeroed in certain cases (e.g. by
guest_halt_poll_ns = 0). If guest_halt_poll_grow_start is zero,
dev->poll_limit_ns will never be bigger than zero.
Use param callback to avoid writing zero to guest_halt_poll_grow_start.
Signed-off-by: Zhenzhong Duan <[email protected]>
---
drivers/cpuidle/governors/haltpoll.c | 22 +++++++++++++++++++++-
1 file changed, 21 insertions(+), 1 deletion(-)
diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c
index 7a703d2..660859d 100644
--- a/drivers/cpuidle/governors/haltpoll.c
+++ b/drivers/cpuidle/governors/haltpoll.c
@@ -20,6 +20,26 @@
#include <linux/module.h>
#include <linux/kvm_para.h>
+static int grow_start_set(const char *val, const struct kernel_param *kp)
+{
+ int ret;
+ unsigned int n;
+
+ if (!val)
+ return -EINVAL;
+
+ ret = kstrtouint(val, 0, &n);
+ if (ret || !n)
+ return -EINVAL;
+
+ return param_set_uint(val, kp);
+}
+
+static const struct kernel_param_ops grow_start_ops = {
+ .set = grow_start_set,
+ .get = param_get_uint,
+};
+
static unsigned int guest_halt_poll_ns __read_mostly = 200000;
module_param(guest_halt_poll_ns, uint, 0644);
@@ -33,7 +53,7 @@
/* value in us to start growing per-cpu halt_poll_ns */
static unsigned int guest_halt_poll_grow_start __read_mostly = 50000;
-module_param(guest_halt_poll_grow_start, uint, 0644);
+module_param_cb(guest_halt_poll_grow_start, &grow_start_ops, &guest_halt_poll_grow_start, 0644);
/* allow shrinking guest halt poll */
static bool guest_halt_poll_allow_shrink __read_mostly = true;
--
1.8.3.1
On Wednesday, November 6, 2019 12:54:59 PM CET Zhenzhong Duan wrote:
> dev->poll_limit_ns could be zeroed in certain cases (e.g. by
> guest_halt_poll_ns = 0). If guest_halt_poll_grow_start is zero,
> dev->poll_limit_ns will never be bigger than zero.
Given that haltpoll_enable_device() sets dev->poll_limit_ns = 0 to start with,
I don't think that the statement above is correct.
On Fri, Nov 15, 2019 at 11:06 AM Rafael J. Wysocki <[email protected]> wrote:
>
> On Wednesday, November 6, 2019 12:54:59 PM CET Zhenzhong Duan wrote:
> > dev->poll_limit_ns could be zeroed in certain cases (e.g. by
> > guest_halt_poll_ns = 0). If guest_halt_poll_grow_start is zero,
> > dev->poll_limit_ns will never be bigger than zero.
>
> Given that haltpoll_enable_device() sets dev->poll_limit_ns = 0 to start with,
> I don't think that the statement above is correct.
Scratch this, I misread it.
On Wed, Nov 6, 2019 at 12:56 PM Zhenzhong Duan
<[email protected]> wrote:
>
> dev->poll_limit_ns could be zeroed in certain cases (e.g. by
> guest_halt_poll_ns = 0). If guest_halt_poll_grow_start is zero,
> dev->poll_limit_ns will never be bigger than zero.
I would rephrase this in the following way:
"If guest_halt_poll_grow_start is zero and dev->poll_limit_ns becomes
zero for any reason, it will never be greater than zero again, so use
..."
The patch itself looks OK to me.
> Use param callback to avoid writing zero to guest_halt_poll_grow_start.
>
> Signed-off-by: Zhenzhong Duan <[email protected]>
> ---
> drivers/cpuidle/governors/haltpoll.c | 22 +++++++++++++++++++++-
> 1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c
> index 7a703d2..660859d 100644
> --- a/drivers/cpuidle/governors/haltpoll.c
> +++ b/drivers/cpuidle/governors/haltpoll.c
> @@ -20,6 +20,26 @@
> #include <linux/module.h>
> #include <linux/kvm_para.h>
>
> +static int grow_start_set(const char *val, const struct kernel_param *kp)
> +{
> + int ret;
> + unsigned int n;
> +
> + if (!val)
> + return -EINVAL;
> +
> + ret = kstrtouint(val, 0, &n);
> + if (ret || !n)
> + return -EINVAL;
> +
> + return param_set_uint(val, kp);
> +}
> +
> +static const struct kernel_param_ops grow_start_ops = {
> + .set = grow_start_set,
> + .get = param_get_uint,
> +};
> +
> static unsigned int guest_halt_poll_ns __read_mostly = 200000;
> module_param(guest_halt_poll_ns, uint, 0644);
>
> @@ -33,7 +53,7 @@
>
> /* value in us to start growing per-cpu halt_poll_ns */
> static unsigned int guest_halt_poll_grow_start __read_mostly = 50000;
> -module_param(guest_halt_poll_grow_start, uint, 0644);
> +module_param_cb(guest_halt_poll_grow_start, &grow_start_ops, &guest_halt_poll_grow_start, 0644);
>
> /* allow shrinking guest halt poll */
> static bool guest_halt_poll_allow_shrink __read_mostly = true;
> --
> 1.8.3.1
>
On 2019/11/15 18:26, Rafael J. Wysocki wrote:
> On Wed, Nov 6, 2019 at 12:56 PM Zhenzhong Duan
> <[email protected]> wrote:
>> dev->poll_limit_ns could be zeroed in certain cases (e.g. by
>> guest_halt_poll_ns = 0). If guest_halt_poll_grow_start is zero,
>> dev->poll_limit_ns will never be bigger than zero.
> I would rephrase this in the following way:
>
> "If guest_halt_poll_grow_start is zero and dev->poll_limit_ns becomes
> zero for any reason, it will never be greater than zero again, so use
> ..."
OK, will do, thanks for your suggestion.
Zhenzhong
>
> The patch itself looks OK to me.
>
>> Use param callback to avoid writing zero to guest_halt_poll_grow_start.
>>
>> Signed-off-by: Zhenzhong Duan <[email protected]>
>> ---
>> drivers/cpuidle/governors/haltpoll.c | 22 +++++++++++++++++++++-
>> 1 file changed, 21 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c
>> index 7a703d2..660859d 100644
>> --- a/drivers/cpuidle/governors/haltpoll.c
>> +++ b/drivers/cpuidle/governors/haltpoll.c
>> @@ -20,6 +20,26 @@
>> #include <linux/module.h>
>> #include <linux/kvm_para.h>
>>
>> +static int grow_start_set(const char *val, const struct kernel_param *kp)
>> +{
>> + int ret;
>> + unsigned int n;
>> +
>> + if (!val)
>> + return -EINVAL;
>> +
>> + ret = kstrtouint(val, 0, &n);
>> + if (ret || !n)
>> + return -EINVAL;
>> +
>> + return param_set_uint(val, kp);
>> +}
>> +
>> +static const struct kernel_param_ops grow_start_ops = {
>> + .set = grow_start_set,
>> + .get = param_get_uint,
>> +};
>> +
>> static unsigned int guest_halt_poll_ns __read_mostly = 200000;
>> module_param(guest_halt_poll_ns, uint, 0644);
>>
>> @@ -33,7 +53,7 @@
>>
>> /* value in us to start growing per-cpu halt_poll_ns */
>> static unsigned int guest_halt_poll_grow_start __read_mostly = 50000;
>> -module_param(guest_halt_poll_grow_start, uint, 0644);
>> +module_param_cb(guest_halt_poll_grow_start, &grow_start_ops, &guest_halt_poll_grow_start, 0644);
>>
>> /* allow shrinking guest halt poll */
>> static bool guest_halt_poll_allow_shrink __read_mostly = true;
>> --
>> 1.8.3.1
>>