Re: [PATCH 10/19] arm64: smp: Use generic HOTPLUG_CORE_SYNC_FULL machinery for CPU onlining

Select HOTPLUG_CORE_SYNC_FULL on arm64 to replace the 'cpu_running'
completion with the generic code for synchronising with secondary CPUs
during boot.

Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/Kconfig           |  2 +-
 arch/arm64/include/asm/smp.h |  1 -
 arch/arm64/kernel/smp.c      | 39 +++++++++++++++++-------------------
 3 files changed, 19 insertions(+), 23 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index b5a51b0ef944..89d1f0f2269c 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig

@@ -230,7 +230,7 @@ config ARM64
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_KPROBES
 	select HAVE_KRETPROBES
-	select HOTPLUG_CORE_SYNC_DEAD if HOTPLUG_CPU
+	select HOTPLUG_CORE_SYNC_FULL
 	select HOTPLUG_SMT if HOTPLUG_CPU
 	select IRQ_DOMAIN
 	select IRQ_FORCED_THREADING

diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
index 10ea4f543069..fe343c30d620 100644
--- a/arch/arm64/include/asm/smp.h
+++ b/arch/arm64/include/asm/smp.h

@@ -12,7 +12,6 @@
 #define CPU_BOOT_STATUS_MASK		((UL(1) << CPU_STUCK_REASON_SHIFT) - 1)
 
 #define CPU_MMU_OFF			(-1)
-#define CPU_BOOT_SUCCESS		(0)
 /* The cpu invoked ops->cpu_die, synchronise it with cpu_kill */
 #define CPU_KILL_ME			(1)
 /* The cpu couldn't die gracefully and is looping in the kernel */

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index ff68640d0c0b..00362ed6e1ab 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c

@@ -108,12 +108,9 @@ static int boot_secondary(unsigned int cpu, struct task_struct *idle)
 	return -EOPNOTSUPP;
 }
 
-static DECLARE_COMPLETION(cpu_running);
-
 int __cpu_up(unsigned int cpu, struct task_struct *idle)
 {
 	int ret;
-	long status;
 
 	/*
 	 * We need to tell the secondary core where to find its stack and the

@@ -124,27 +121,24 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 
 	/* Now bring the CPU into our world */
 	ret = boot_secondary(cpu, idle);
-	if (ret) {
-		if (ret != -EPERM)
-			pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
-		return ret;
-	}
+	if (ret && ret != -EPERM)
+		pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
+	return ret;
+}
 
-	/*
-	 * CPU was successfully started, wait for it to come online or
-	 * time out.
-	 */
-	wait_for_completion_timeout(&cpu_running,
-				    msecs_to_jiffies(5000));
-	if (cpu_online(cpu))
-		return 0;
+void arch_cpuhp_cleanup_kick_cpu(unsigned int cpu, bool is_alive)
+{
+	long status;
+
+	if (is_alive)
+		return;
 
-	pr_crit("CPU%u: failed to come online\n", cpu);
 	secondary_data.task = NULL;
 	status = READ_ONCE(secondary_data.status);
 	if (status == CPU_MMU_OFF)
 		status = READ_ONCE(__early_cpu_boot_status);
 
+	/* A CPU has failed to boot. Try to figure out what happened. */
 	switch (status & CPU_BOOT_STATUS_MASK) {
 	default:
 		pr_err("CPU%u: failed in unknown state : 0x%lx\n",

@@ -171,8 +165,6 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 	case CPU_PANIC_KERNEL:
 		panic("CPU%u detected unsupported configuration\n", cpu);
 	}
-
-	return -EIO;
 }
 
 static void init_gic_priority_masking(void)

@@ -234,6 +226,13 @@ asmlinkage notrace void secondary_start_kernel(void)
 	 * Log the CPU info before it is marked online and might get read.
 	 */
 	cpuinfo_store_cpu();
+
+	/*
+	 * Synchronise with the core bringing us online so that it knows
+	 * we made it into the kernel. We're still not 'online'.
+	 */
+	cpuhp_ap_sync_alive();
+
 	update_cpu_features(cpu);
 	store_cpu_topology(cpu);
 

@@ -255,9 +254,7 @@ asmlinkage notrace void secondary_start_kernel(void)
 	pr_info("CPU%u: Booted secondary processor 0x%010lx [0x%08x]\n",
 					 cpu, (unsigned long)mpidr,
 					 read_cpuid_id());
-	update_cpu_boot_status(CPU_BOOT_SUCCESS);
 	set_cpu_online(cpu, true);
-	complete(&cpu_running);