linux-kernel - [PATCH V2] arm64: psci: Reduce waiting time of cpu_psci_cpu

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Date:   Sat, 21 Sep 2019 19:21:17 +0800
From:   Yunfeng Ye <yeyunfeng@...wei.com>
To:     David Laight <David.Laight@...LAB.COM>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will@...nel.org" <will@...nel.org>,
        "kstewart@...uxfoundation.org" <kstewart@...uxfoundation.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "wuyun.wu@...wei.com" <wuyun.wu@...wei.com>
Subject: [PATCH V2] arm64: psci: Reduce waiting time of cpu_psci_cpu_kill()

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@...wei.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(-)

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