From: Atish Patra <atish.patra@wdc.com>
Date: Tue, 2 Oct 2018 19:15:03 +0000 (-0700)
Subject: RISC-V: Use WRITE_ONCE instead of direct access
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=a37d56fc401108f39dec9ba83ed923a453937a26;p=linux.git

RISC-V: Use WRITE_ONCE instead of direct access

The secondary harts spin on couple of per cpu variables until both of
these are non-zero so it's not necessary to have any ordering here.
However, WRITE_ONCE should be used to avoid tearing.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
---

diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 17e748312afd5..1e478615017c8 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -81,8 +81,9 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle)
 	 * the spinning harts that they can continue the boot process.
 	 */
 	smp_mb();
-	__cpu_up_stack_pointer[cpu] = task_stack_page(tidle) + THREAD_SIZE;
-	__cpu_up_task_pointer[cpu] = tidle;
+	WRITE_ONCE(__cpu_up_stack_pointer[cpu],
+		  task_stack_page(tidle) + THREAD_SIZE);
+	WRITE_ONCE(__cpu_up_task_pointer[cpu], tidle);
 
 	while (!cpu_online(cpu))
 		cpu_relax();