Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Atish Patra <atish.patra@wdc.com>
To:     linux-riscv@lists.infradead.org
Cc:     Atish Patra <atish.patra@wdc.com>,
        Alan Kao <alankao@andestech.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Andreas Schwab <schwab@suse.de>,
        Anup Patel <anup@brainfault.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Dmitriy Cherkasov <dmitriy@oss-tech.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Jason Cooper <jason@lakedaemon.net>,
        Johan Hovold <johan@kernel.org>, linux-kernel@vger.kernel.org,
        Marc Zyngier <marc.zyngier@arm.com>,
        Palmer Dabbelt <palmer@sifive.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: [v5 PATCH 1/8] RISC-V: Do not wait indefinitely in __cpu_up
Date:   Wed, 13 Feb 2019 12:18:05 -0800
Message-Id: <1550089092-28783-2-git-send-email-atish.patra@wdc.com>
In-Reply-To: <1550089092-28783-1-git-send-email-atish.patra@wdc.com>
References: <1550089092-28783-1-git-send-email-atish.patra@wdc.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In SMP path, __cpu_up waits for other CPU to come online indefinitely.
This is wrong as other CPU might be disabled in machine mode and
possible CPU is set to the cpus present in DT.

Introduce a completion variable and waits only for a second.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/kernel/smpboot.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 6e281325..d369b669 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -39,6 +39,7 @@
 
 void *__cpu_up_stack_pointer[NR_CPUS];
 void *__cpu_up_task_pointer[NR_CPUS];
+static DECLARE_COMPLETION(cpu_running);
 
 void __init smp_prepare_boot_cpu(void)
 {
@@ -77,6 +78,7 @@ void __init setup_smp(void)
 
 int __cpu_up(unsigned int cpu, struct task_struct *tidle)
 {
+	int ret = 0;
 	int hartid = cpuid_to_hartid_map(cpu);
 	tidle->thread_info.cpu = cpu;
 
@@ -92,10 +94,16 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle)
 		  task_stack_page(tidle) + THREAD_SIZE);
 	WRITE_ONCE(__cpu_up_task_pointer[hartid], tidle);
 
-	while (!cpu_online(cpu))
-		cpu_relax();
+	lockdep_assert_held(&cpu_running);
+	wait_for_completion_timeout(&cpu_running,
+					    msecs_to_jiffies(1000));
 
-	return 0;
+	if (!cpu_online(cpu)) {
+		pr_crit("CPU%u: failed to come online\n", cpu);
+		ret = -EIO;
+	}
+
+	return ret;
 }
 
 void __init smp_cpus_done(unsigned int max_cpus)
@@ -121,6 +129,7 @@ asmlinkage void __init smp_callin(void)
 	 * a local TLB flush right now just in case.
 	 */
 	local_flush_tlb_all();
+	complete(&cpu_running);
 	/*
 	 * Disable preemption before enabling interrupts, so we don't try to
 	 * schedule a CPU that hasn't actually started yet.
-- 
2.7.4