[V2] arm64: psci: Reduce waiting time of cpu_psci_cpu_kill()
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Message ID 18068756-0f39-6388-3290-cf03746e767d@huawei.com
State New
Headers show
Series
  • [V2] arm64: psci: Reduce waiting time of cpu_psci_cpu_kill()
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Commit Message

Yunfeng Ye Sept. 21, 2019, 11:21 a.m. UTC
If psci_ops.affinity_info() fails, it will sleep 10ms, which will not
take so long in the right case. Use usleep_range() instead of msleep(),
reduce the waiting time, and give a chance to busy wait before sleep.

Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
---
V1->V2:
- use usleep_range() instead of udelay() after waiting for a while

 arch/arm64/kernel/psci.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

Comments

Will Deacon Oct. 15, 2019, 4:23 p.m. UTC | #1
Hi,

On Sat, Sep 21, 2019 at 07:21:17PM +0800, Yunfeng Ye wrote:
> If psci_ops.affinity_info() fails, it will sleep 10ms, which will not
> take so long in the right case. Use usleep_range() instead of msleep(),
> reduce the waiting time, and give a chance to busy wait before sleep.

Can you elaborate on "the right case" please? It's not clear to me
exactly what problem you're solving here.

I've also added Sudeep to the thread, since I'd like his ack on the change.

Will

>  arch/arm64/kernel/psci.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
> index c9f72b2..99b3122 100644
> --- a/arch/arm64/kernel/psci.c
> +++ b/arch/arm64/kernel/psci.c
> @@ -82,6 +82,7 @@ static void cpu_psci_cpu_die(unsigned int cpu)
>  static int cpu_psci_cpu_kill(unsigned int cpu)
>  {
>  	int err, i;
> +	unsigned long timeout;
> 
>  	if (!psci_ops.affinity_info)
>  		return 0;
> @@ -91,16 +92,24 @@ static int cpu_psci_cpu_kill(unsigned int cpu)
>  	 * while it is dying. So, try again a few times.
>  	 */
> 
> -	for (i = 0; i < 10; i++) {
> +	i = 0;
> +	timeout = jiffies + msecs_to_jiffies(100);
> +	do {
>  		err = psci_ops.affinity_info(cpu_logical_map(cpu), 0);
>  		if (err == PSCI_0_2_AFFINITY_LEVEL_OFF) {
>  			pr_info("CPU%d killed.\n", cpu);
>  			return 0;
>  		}
> 
> -		msleep(10);
> -		pr_info("Retrying again to check for CPU kill\n");
> -	}
> +		/* busy-wait max 1ms */
> +		if (i++ < 100) {
> +			cond_resched();
> +			udelay(10);
> +			continue;
> +		}
> +
> +		usleep_range(100, 1000);
> +	} while (time_before(jiffies, timeout));
> 
>  	pr_warn("CPU%d may not have shut down cleanly (AFFINITY_INFO reports %d)\n",
>  			cpu, err);
> -- 
> 2.7.4.huawei.3
>

Patch
diff mbox series

diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
index c9f72b2..99b3122 100644
--- a/arch/arm64/kernel/psci.c
+++ b/arch/arm64/kernel/psci.c
@@ -82,6 +82,7 @@  static void cpu_psci_cpu_die(unsigned int cpu)
 static int cpu_psci_cpu_kill(unsigned int cpu)
 {
 	int err, i;
+	unsigned long timeout;

 	if (!psci_ops.affinity_info)
 		return 0;
@@ -91,16 +92,24 @@  static int cpu_psci_cpu_kill(unsigned int cpu)
 	 * while it is dying. So, try again a few times.
 	 */

-	for (i = 0; i < 10; i++) {
+	i = 0;
+	timeout = jiffies + msecs_to_jiffies(100);
+	do {
 		err = psci_ops.affinity_info(cpu_logical_map(cpu), 0);
 		if (err == PSCI_0_2_AFFINITY_LEVEL_OFF) {
 			pr_info("CPU%d killed.\n", cpu);
 			return 0;
 		}

-		msleep(10);
-		pr_info("Retrying again to check for CPU kill\n");
-	}
+		/* busy-wait max 1ms */
+		if (i++ < 100) {
+			cond_resched();
+			udelay(10);
+			continue;
+		}
+
+		usleep_range(100, 1000);
+	} while (time_before(jiffies, timeout));

 	pr_warn("CPU%d may not have shut down cleanly (AFFINITY_INFO reports %d)\n",
 			cpu, err);