On 2019/11/15 18:26, Rafael J. Wysocki wrote:
On Wed, Nov 6, 2019 at 12:56 PM Zhenzhong Duan
<zhenzhong.duan@xxxxxxxxxx> 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 <zhenzhong.duan@xxxxxxxxxx>
---
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
