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From:   Cheng Jian <cj.chengjian@huawei.com>
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Subject: [PATCH] sched/arm64: store cpu topology before notify_cpu_starting
Date:   Wed, 1 Apr 2020 11:42:15 +0000
Message-ID: <20200401114215.36640-1-cj.chengjian@huawei.com>
In-Reply-To: <855831b59e1b3774b11c3e33050eac4cc4639f06.1583332765.git.vpillai@digitalocean.com>
References: <855831b59e1b3774b11c3e33050eac4cc4639f06.1583332765.git.vpillai@digitalocean.com>
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when SCHED_CORE enabled, sched_cpu_starting() uses thread_sibling as
SMT_MASK to initialize rq->core, but only after store_cpu_topology(),
the thread_sibling is ready for use.

	notify_cpu_starting()
	    -> sched_cpu_starting()	# use thread_sibling

	store_cpu_topology(cpu)
	    -> update_siblings_masks	# set thread_sibling

Fix this by doing notify_cpu_starting later, just like x86 do.

Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
---
 arch/arm64/kernel/smp.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 5407bf5d98ac..a427c14e82af 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -236,13 +236,18 @@ asmlinkage notrace void secondary_start_kernel(void)
 	cpuinfo_store_cpu();
 
 	/*
-	 * Enable GIC and timers.
+	 * Store cpu topology before notify_cpu_starting,
+	 * CPUHP_AP_SCHED_STARTING requires SMT topology
+	 * been initialized for SCHED_CORE.
 	 */
-	notify_cpu_starting(cpu);
-
 	store_cpu_topology(cpu);
 	numa_add_cpu(cpu);
 
+	/*
+	 * Enable GIC and timers.
+	 */
+	notify_cpu_starting(cpu);
+
 	/*
 	 * OK, now it's safe to let the boot CPU continue.  Wait for
 	 * the CPU migration code to notice that the CPU is online
-- 
2.17.1