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Subject[RFC PATCH v3 06/12] arm64: smp: use SMP crash-stop common code
Date
Make arm64 use the SMP common implementation of crash_smp_send_stop() and
its generic logic, by removing the arm64 crash_smp_send_stop() definition
and providing the needed arch specific helpers.

Additionally, simplify the arch-specific stop and crash dump ISRs backends
(which are in charge of effectively receiving and interpreting the
stop/crash messages) and unify them as much as possible.

Using the SMP common code, it is no more needed to make use of an atomic_t
counter to make sure that each CPU had time to perform its crash dump
related shutdown-ops before the world ends: simply take care to synchronize
on cpu_online_mask, and add proper explicit memory barriers where needed.

Moreover, remove arm64 specific smp_crash_stop_failed() helper as a whole
and rely on the common code provided homonym function to lookup the state
of an ongoing crash_stop operation.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
v1 --> v2
- added attempt_num param to arch_smp_crash_call()
---
arch/arm64/include/asm/smp.h | 2 -
arch/arm64/kernel/smp.c | 100 +++++++++--------------------------
2 files changed, 26 insertions(+), 76 deletions(-)

diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
index a0c8a0b65259..d98c409f9225 100644
--- a/arch/arm64/include/asm/smp.h
+++ b/arch/arm64/include/asm/smp.h
@@ -150,8 +150,6 @@ static inline void cpu_panic_kernel(void)
*/
bool cpus_are_stuck_in_kernel(void);

-extern void crash_smp_send_stop(void);
-extern bool smp_crash_stop_failed(void);

#endif /* ifndef __ASSEMBLY__ */

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 7c1869161b5e..edb2de85507a 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -830,12 +830,30 @@ void arch_irq_work_raise(void)
}
#endif

-static void local_cpu_stop(void)
+static void local_cpu_crash_or_stop(struct pt_regs *crash_regs)
{
- set_cpu_online(smp_processor_id(), false);
+ unsigned int cpu = smp_processor_id();

- local_daif_mask();
+ if (IS_ENABLED(CONFIG_KEXEC_CORE) && crash_regs) {
+#ifdef CONFIG_KEXEC_CORE
+ /* crash stop requested: save regs before going offline */
+ crash_save_cpu(crash_regs, cpu);
+#endif
+ local_irq_disable();
+ } else {
+ local_daif_mask();
+ }
sdei_mask_local_cpu();
+ /* ensure dumped regs are visible once cpu is seen offline */
+ smp_wmb();
+ set_cpu_online(cpu, false);
+ /* ensure all writes are globally visible before cpu parks */
+ wmb();
+#if defined(CONFIG_KEXEC_CORE) && defined(CONFIG_HOTPLUG_CPU)
+ if (cpu_ops[cpu]->cpu_die)
+ cpu_ops[cpu]->cpu_die(cpu);
+#endif
+ /* just in case */
cpu_park_loop();
}

@@ -846,31 +864,7 @@ static void local_cpu_stop(void)
*/
void panic_smp_self_stop(void)
{
- local_cpu_stop();
-}
-
-#ifdef CONFIG_KEXEC_CORE
-static atomic_t waiting_for_crash_ipi = ATOMIC_INIT(0);
-#endif
-
-static void ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs)
-{
-#ifdef CONFIG_KEXEC_CORE
- crash_save_cpu(regs, cpu);
-
- atomic_dec(&waiting_for_crash_ipi);
-
- local_irq_disable();
- sdei_mask_local_cpu();
-
-#ifdef CONFIG_HOTPLUG_CPU
- if (cpu_ops[cpu]->cpu_die)
- cpu_ops[cpu]->cpu_die(cpu);
-#endif
-
- /* just in case */
- cpu_park_loop();
-#endif
+ local_cpu_crash_or_stop(NULL);
}

/*
@@ -899,14 +893,14 @@ void handle_IPI(int ipinr, struct pt_regs *regs)

case IPI_CPU_STOP:
irq_enter();
- local_cpu_stop();
+ local_cpu_crash_or_stop(NULL);
irq_exit();
break;

case IPI_CPU_CRASH_STOP:
if (IS_ENABLED(CONFIG_KEXEC_CORE)) {
irq_enter();
- ipi_cpu_crash_stop(cpu, regs);
+ local_cpu_crash_or_stop(regs);

unreachable();
}
@@ -968,52 +962,10 @@ void arch_smp_stop_call(cpumask_t *cpus, unsigned int __unused)
smp_cross_call(cpus, IPI_CPU_STOP);
}

-#ifdef CONFIG_KEXEC_CORE
-void crash_smp_send_stop(void)
+void arch_smp_crash_call(cpumask_t *cpus, unsigned int __unused)
{
- static int cpus_stopped;
- cpumask_t mask;
- unsigned long timeout;
-
- /*
- * This function can be called twice in panic path, but obviously
- * we execute this only once.
- */
- if (cpus_stopped)
- return;
-
- cpus_stopped = 1;
-
- if (num_online_cpus() == 1) {
- sdei_mask_local_cpu();
- return;
- }
-
- cpumask_copy(&mask, cpu_online_mask);
- cpumask_clear_cpu(smp_processor_id(), &mask);
-
- atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
-
- pr_crit("SMP: stopping secondary CPUs\n");
- smp_cross_call(&mask, IPI_CPU_CRASH_STOP);
-
- /* Wait up to one second for other CPUs to stop */
- timeout = USEC_PER_SEC;
- while ((atomic_read(&waiting_for_crash_ipi) > 0) && timeout--)
- udelay(1);
-
- if (atomic_read(&waiting_for_crash_ipi) > 0)
- pr_warn("SMP: failed to stop secondary CPUs %*pbl\n",
- cpumask_pr_args(&mask));
-
- sdei_mask_local_cpu();
-}
-
-bool smp_crash_stop_failed(void)
-{
- return (atomic_read(&waiting_for_crash_ipi) > 0);
+ smp_cross_call(cpus, IPI_CPU_CRASH_STOP);
}
-#endif

/*
* not supported here
--
2.17.1
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