linux-kernel - [RFC PATCH v3 11/12] arm: smp: use SMP crash-stop common code

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Date:   Thu, 19 Dec 2019 12:19:04 +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 11/12] arm: smp: use SMP crash-stop common code

Make arm use the SMP common implementation of crash_smp_send_stop() and
its generic logic, by removing the arm crash_smp_send_stop() definition
and providing the needed arch specific helpers.

Signed-off-by: Cristian Marussi <cristian.marussi@....com>
---
 arch/arm/kernel/machine_kexec.c | 29 ++++++++---------------------
 1 file changed, 8 insertions(+), 21 deletions(-)

diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index 76300f3813e8..5289984e3941 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -29,8 +29,6 @@ extern unsigned long kexec_indirection_page;
 extern unsigned long kexec_mach_type;
 extern unsigned long kexec_boot_atags;
 
-static atomic_t waiting_for_crash_ipi;
-
 /*
  * Provide a dummy crash_notes definition while crash dump arrives to arm.
  * This prevents breakage of crash_notes attribute in kernel/ksysfs.c.
@@ -89,34 +87,23 @@ void machine_crash_nonpanic_core(void *unused)
 	crash_save_cpu(&regs, smp_processor_id());
 	flush_cache_all();
 
+	/* ensure saved regs writes are visible before going offline */
+	smp_wmb();
 	set_cpu_online(smp_processor_id(), false);
-	atomic_dec(&waiting_for_crash_ipi);
 
+	/* ensure all writes visible before parking */
+	wmb();
 	while (1) {
 		cpu_relax();
 		wfe();
 	}
 }
 
-void crash_smp_send_stop(void)
+void arch_smp_crash_call(cpumask_t *cpus, unsigned int __unused)
 {
-	static int cpus_stopped;
-	unsigned long msecs;
-
-	if (cpus_stopped)
-		return;
-
-	atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
-	smp_call_function(machine_crash_nonpanic_core, NULL, false);
-	msecs = 1000; /* Wait at most a second for the other cpus to stop */
-	while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
-		mdelay(1);
-		msecs--;
-	}
-	if (atomic_read(&waiting_for_crash_ipi) > 0)
-		pr_warn("Non-crashing CPUs did not react to IPI\n");
-
-	cpus_stopped = 1;
+	preempt_disable();
+	smp_call_function_many(cpus, machine_crash_nonpanic_core, NULL, false);
+	preempt_enable();
 }
 
 static void machine_kexec_mask_interrupts(void)
-- 
2.17.1