linux-kernel - [PATCH] arm64: make secondary_start

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Message-ID: <1528794457-14129-1-git-send-email-zhizhouzhang@asrmicro.com>
Date:   Tue, 12 Jun 2018 17:07:37 +0800
From:   Zhizhou Zhang <zhizhouzhang@...micro.com>
To:     <catalin.marinas@....com>, <will.deacon@....com>,
        <james.morse@....com>, <mark.rutland@....com>,
        <julien.thierry@....com>, <suzuki.poulose@....com>,
        <hoeun.ryu@...il.com>, <ard.biesheuvel@...aro.org>
CC:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <zhizhouzhang@...micro.com>
Subject: [PATCH] arm64: make secondary_start_kernel() notrace

We can't call function trace hook before setup percpu offset.
When entering secondary_start_kernel(), percpu offset has not
been initialized.  So this lead hotplug malfunction.
Here is the flow to reproduce this bug:

echo 0 > /sys/devices/system/cpu/cpu1/online
echo function > /sys/kernel/debug/tracing/current_tracer
echo 1 > /sys/kernel/debug/tracing/tracing_on
echo 1 > /sys/devices/system/cpu/cpu1/online

Signed-off-by: Zhizhou Zhang <zhizhouzhang@...micro.com>
---
 arch/arm64/kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index f3e2e3ae..11b0f30 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -179,7 +179,7 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
  * This is the secondary CPU boot entry.  We're using this CPUs
  * idle thread stack, but a set of temporary page tables.
  */
-asmlinkage void secondary_start_kernel(void)
+notrace asmlinkage void secondary_start_kernel(void)
 {
 	u64 mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;
 	struct mm_struct *mm = &init_mm;
-- 
1.9.1