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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Yunfeng Ye > Sent: 11 September 2019 09:50 > 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 > --- > 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); You really don't want to be doing 10000 udelay(10) before giving up. If udelay(10) is long enough for the normal case, then do that once. After that use usleep_range(). David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel