linux-kernel - [PATCH 3/3] MIPS: smp-cps: Don't BUG if a CPU fails to start

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Date:   Fri, 4 Nov 2016 09:28:58 +0000
From:   Matt Redfearn <matt.redfearn@...tec.com>
To:     Ralf Baechle <ralf@...ux-mips.org>, <linux-mips@...ux-mips.org>
CC:     Matt Redfearn <matt.redfearn@...tec.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        <linux-kernel@...r.kernel.org>,
        James Hogan <james.hogan@...tec.com>,
        Paul Burton <paul.burton@...tec.com>,
        Qais Yousef <qsyousef@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 3/3] MIPS: smp-cps: Don't BUG if a CPU fails to start

If there is no online CPU within a core which could receive the IPI to
start another VP in that core, a BUG() is triggered. Instead print a
warning and gracefully handle the failure such that the system remains
usable, albeit without the requested secondary CPU.

Signed-off-by: Matt Redfearn <matt.redfearn@...tec.com>
---

 arch/mips/kernel/smp-cps.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kernel/smp-cps.c b/arch/mips/kernel/smp-cps.c
index 44339b470ef4..a2544c2394e4 100644
--- a/arch/mips/kernel/smp-cps.c
+++ b/arch/mips/kernel/smp-cps.c
@@ -326,7 +326,11 @@ static void cps_boot_secondary(int cpu, struct task_struct *idle)
 			if (cpu_online(remote))
 				break;
 		}
-		BUG_ON(remote >= NR_CPUS);
+		if (remote >= NR_CPUS) {
+			pr_crit("No online CPU in core %u to start CPU%d\n",
+				core, cpu);
+			goto out;
+		}
 
 		err = smp_call_function_single(remote, remote_vpe_boot,
 					       NULL, 1);
-- 
2.7.4