linux-kernel - [PATCH v6 05/14] RISC-V: Disable preemption before enabling interrupts

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Message-Id: <1538507707-22299-6-git-send-email-atish.patra@wdc.com>
Date:   Tue,  2 Oct 2018 12:14:58 -0700
From:   Atish Patra <atish.patra@....com>
To:     linux-riscv@...ts.infradead.org, palmer@...ive.com
Cc:     anup@...infault.org, hch@...radead.org,
        linux-kernel@...r.kernel.org, atish.patra@....com
Subject: [PATCH v6 05/14] RISC-V: Disable preemption before enabling interrupts

Currently, irq is enabled before preemption disabling happens.
If the scheduler fired right here and cpu is scheduled then it
may blow up.

Signed-off-by: Palmer Dabbelt <palmer@...ive.com>
[Atish: Commit text and code comment formatting update]
Signed-off-by: Atish Patra <atish.patra@....com>
Reviewed-by: Christoph Hellwig <hch@....de>
---
 arch/riscv/kernel/smpboot.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 712e9ca8..670749ec 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -111,7 +111,11 @@ asmlinkage void __init smp_callin(void)
 	 * a local TLB flush right now just in case.
 	 */
 	local_flush_tlb_all();
-	local_irq_enable();
+	/*
+	 * Disable preemption before enabling interrupts, so we don't try to
+	 * schedule a CPU that hasn't actually started yet.
+	 */
 	preempt_disable();
+	local_irq_enable();
 	cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
-- 
2.7.4