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Subject[PATCH] x86/smpboot: set topology CPU mask before use.
Date
From: Zhang Ning <ning.a.zhang@intel.com>

we detect topology CPU mask in tsc is used before it is set, it leads
to longer bootup time.

let's check the code.

smpboot.c:smp_callin()
---> calibarate.c:calibrate_delay()
---> tsc.c: calibrate_delay_is_known()
---> topology_core_cpumask(): read topology CPU mask
---> set_cpu_sibling_map(raw_smp_processor_id())
---> cpumask_set_cpu(cpu, topology_core_cpumask(cpu));

from the calling chain, we know topology CPU mask is used before it
actually set.

So move set_cpu_sibling_map before calibrate_delay.

Change-Id: I4eb8facb8751fe7aa2c6d2eac32437266d92ec00
Signed-off-by: Zhang Ning <ning.a.zhang@intel.com>
---
arch/x86/kernel/smpboot.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 36171bcd91f8..acee1ca3ef43 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -181,6 +181,12 @@ static void smp_callin(void)
smp_store_cpu_info(cpuid);

/*
+ * This must be done before setting cpu_online_mask
+ * or calling notify_cpu_starting.
+ */
+ set_cpu_sibling_map(raw_smp_processor_id());
+
+ /*
* Get our bogomips.
* Update loops_per_jiffy in cpu_data. Previous call to
* smp_store_cpu_info() stored a value that is close but not as
@@ -190,11 +196,7 @@ static void smp_callin(void)
cpu_data(cpuid).loops_per_jiffy = loops_per_jiffy;
pr_debug("Stack at about %p\n", &cpuid);

- /*
- * This must be done before setting cpu_online_mask
- * or calling notify_cpu_starting.
- */
- set_cpu_sibling_map(raw_smp_processor_id());
+
wmb();

notify_cpu_starting(cpuid);
--
2.11.0
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