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Subject[PATCH] arm64: psci: Use udelay() instead of msleep() to reduce waiting time
Date
We want to reduce the time of cpu_down() for saving power, found that
cpu_psci_cpu_kill() cost 10ms after psci_ops.affinity_info() fail.

Normally the time cpu dead is very short, it is no need to wait 10ms.
so use udelay 10us to instead msleep 10ms in every waiting loop, and add
cond_resched() to give a chance to run a higher-priority process.

Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
---
arch/arm64/kernel/psci.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
index 85ee7d0..9e9d8a6 100644
--- a/arch/arm64/kernel/psci.c
+++ b/arch/arm64/kernel/psci.c
@@ -86,15 +86,15 @@ 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++) {
+ for (i = 0; i < 10000; i++) {
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");
+ cond_resched();
+ udelay(10);
}

pr_warn("CPU%d may not have shut down cleanly (AFFINITY_INFO reports %d)\n",
--
1.8.3.1
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