linux-kernel - [RFC PATCH v3 10/12] arm: smp: use generic SMP stop common code

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Date:   Thu, 19 Dec 2019 12:19:03 +0000
From:   Cristian Marussi <cristian.marussi@....com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arch@...r.kernel.org, mark.rutland@....com,
        peterz@...radead.org, catalin.marinas@....com,
        takahiro.akashi@...aro.org, james.morse@....com,
        hidehiro.kawai.ez@...achi.com, tglx@...utronix.de, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org, mingo@...hat.com,
        x86@...nel.org, dzickus@...hat.com, ehabkost@...hat.com,
        linux@...linux.org.uk, davem@...emloft.net,
        sparclinux@...r.kernel.org, hch@...radead.org
Subject: [RFC PATCH v3 10/12] arm: smp: use generic SMP stop common code

Make arm use the generic SMP-stop logic provided by common code
unified smp_send_stop() function.

Signed-off-by: Cristian Marussi <cristian.marussi@....com>
---
v2 --> v3
- conflicts
- added missing barriers
---
 arch/arm/Kconfig      |  1 +
 arch/arm/kernel/smp.c | 22 ++++++----------------
 2 files changed, 7 insertions(+), 16 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index ba75e3661a41..40f6961c449c 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -35,6 +35,7 @@ config ARM
 	select ARCH_USE_CMPXCHG_LOCKREF
 	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
 	select ARCH_WANT_IPC_PARSE_VERSION
+	select ARCH_USE_COMMON_SMP_STOP
 	select BINFMT_FLAT_ARGVP_ENVP_ON_STACK
 	select BUILDTIME_EXTABLE_SORT if MMU
 	select CLONE_BACKWARDS
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 46e1be9e57a8..f03e9bbf4116 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -598,6 +598,8 @@ static void ipi_cpu_stop(unsigned int cpu)
 	}
 
 	set_cpu_online(cpu, false);
+	/* ensure all writes are globally visible before cpu parks */
+	wmb();
 
 	local_fiq_disable();
 	local_irq_disable();
@@ -705,23 +707,9 @@ void smp_send_reschedule(int cpu)
 	smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
 }
 
-void smp_send_stop(void)
+void arch_smp_stop_call(cpumask_t *cpus, unsigned int __unused)
 {
-	unsigned long timeout;
-	struct cpumask mask;
-
-	cpumask_copy(&mask, cpu_online_mask);
-	cpumask_clear_cpu(smp_processor_id(), &mask);
-	if (!cpumask_empty(&mask))
-		smp_cross_call(&mask, IPI_CPU_STOP);
-
-	/* Wait up to one second for other CPUs to stop */
-	timeout = USEC_PER_SEC;
-	while (num_online_cpus() > 1 && timeout--)
-		udelay(1);
-
-	if (num_online_cpus() > 1)
-		pr_warn("SMP: failed to stop secondary CPUs\n");
+	smp_cross_call(cpus, IPI_CPU_STOP);
 }
 
 /* In case panic() and panic() called at the same time on CPU1 and CPU2,
@@ -735,6 +723,8 @@ void panic_smp_self_stop(void)
 	pr_debug("CPU %u will stop doing anything useful since another CPU has paniced\n",
 	         smp_processor_id());
 	set_cpu_online(smp_processor_id(), false);
+	/* ensure all writes visible before parking */
+	wmb();
 	while (1)
 		cpu_relax();
 }
-- 
2.17.1