[PATCH V4 2/3] riscv: kexec: Fixup crash_smp_send_stop without multi cores
guoren at kernel.org
guoren at kernel.org
Tue Sep 20 20:31:33 PDT 2022
From: Guo Ren <guoren at linux.alibaba.com>
Current crash_smp_send_stop is the same as the generic one in
kernel/panic and misses crash_save_cpu in percpu. This patch is inspired
by 78fd584cdec0 ("arm64: kdump: implement machine_crash_shutdown()")
and adds the same mechanism for riscv.
Fixes: ad943893d5f1 ("RISC-V: Fixup schedule out issue in machine_crash_shutdown()")
Reviewed-by: Xianting Tian <xianting.tian at linux.alibaba.com>
Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
Signed-off-by: Guo Ren <guoren at kernel.org>
Cc: Nick Kossifidis <mick at ics.forth.gr>
---
arch/riscv/include/asm/smp.h | 3 +
arch/riscv/kernel/machine_kexec.c | 21 ++-----
arch/riscv/kernel/smp.c | 97 ++++++++++++++++++++++++++++++-
3 files changed, 103 insertions(+), 18 deletions(-)
diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
index d3443be7eedc..3831b638ecab 100644
--- a/arch/riscv/include/asm/smp.h
+++ b/arch/riscv/include/asm/smp.h
@@ -50,6 +50,9 @@ void riscv_set_ipi_ops(const struct riscv_ipi_ops *ops);
/* Clear IPI for current CPU */
void riscv_clear_ipi(void);
+/* Check other CPUs stop or not */
+bool smp_crash_stop_failed(void);
+
/* Secondary hart entry */
asmlinkage void smp_callin(void);
diff --git a/arch/riscv/kernel/machine_kexec.c b/arch/riscv/kernel/machine_kexec.c
index db41c676e5a2..2d139b724bc8 100644
--- a/arch/riscv/kernel/machine_kexec.c
+++ b/arch/riscv/kernel/machine_kexec.c
@@ -140,22 +140,6 @@ void machine_shutdown(void)
#endif
}
-/* Override the weak function in kernel/panic.c */
-void crash_smp_send_stop(void)
-{
- static int cpus_stopped;
-
- /*
- * This function can be called twice in panic path, but obviously
- * we execute this only once.
- */
- if (cpus_stopped)
- return;
-
- smp_send_stop();
- cpus_stopped = 1;
-}
-
static void machine_kexec_mask_interrupts(void)
{
unsigned int i;
@@ -230,6 +214,11 @@ machine_kexec(struct kimage *image)
void *control_code_buffer = page_address(image->control_code_page);
riscv_kexec_method kexec_method = NULL;
+#ifdef CONFIG_SMP
+ WARN(smp_crash_stop_failed(),
+ "Some CPUs may be stale, kdump will be unreliable.\n");
+#endif
+
if (image->type != KEXEC_TYPE_CRASH)
kexec_method = control_code_buffer;
else
diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 760a64518c58..8c3b59f1f9b8 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -12,6 +12,7 @@
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/module.h>
+#include <linux/kexec.h>
#include <linux/profile.h>
#include <linux/smp.h>
#include <linux/sched.h>
@@ -22,11 +23,13 @@
#include <asm/sbi.h>
#include <asm/tlbflush.h>
#include <asm/cacheflush.h>
+#include <asm/cpu_ops.h>
enum ipi_message_type {
IPI_RESCHEDULE,
IPI_CALL_FUNC,
IPI_CPU_STOP,
+ IPI_CPU_CRASH_STOP,
IPI_IRQ_WORK,
IPI_TIMER,
IPI_MAX
@@ -71,6 +74,32 @@ static void ipi_stop(void)
wait_for_interrupt();
}
+#ifdef CONFIG_KEXEC_CORE
+static atomic_t waiting_for_crash_ipi = ATOMIC_INIT(0);
+
+static inline void ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs)
+{
+ crash_save_cpu(regs, cpu);
+
+ atomic_dec(&waiting_for_crash_ipi);
+
+ local_irq_disable();
+
+#ifdef CONFIG_HOTPLUG_CPU
+ if (cpu_has_hotplug(cpu))
+ cpu_ops[cpu]->cpu_stop();
+#endif
+
+ for(;;)
+ wait_for_interrupt();
+}
+#else
+static inline void ipi_cpu_crash_stop(unsigned int cpu, struct pt_regs *regs)
+{
+ unreachable();
+}
+#endif
+
static const struct riscv_ipi_ops *ipi_ops __ro_after_init;
void riscv_set_ipi_ops(const struct riscv_ipi_ops *ops)
@@ -124,8 +153,9 @@ void arch_irq_work_raise(void)
void handle_IPI(struct pt_regs *regs)
{
- unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;
- unsigned long *stats = ipi_data[smp_processor_id()].stats;
+ unsigned int cpu = smp_processor_id();
+ unsigned long *pending_ipis = &ipi_data[cpu].bits;
+ unsigned long *stats = ipi_data[cpu].stats;
riscv_clear_ipi();
@@ -154,6 +184,10 @@ void handle_IPI(struct pt_regs *regs)
ipi_stop();
}
+ if (ops & (1 << IPI_CPU_CRASH_STOP)) {
+ ipi_cpu_crash_stop(cpu, get_irq_regs());
+ }
+
if (ops & (1 << IPI_IRQ_WORK)) {
stats[IPI_IRQ_WORK]++;
irq_work_run();
@@ -176,6 +210,7 @@ static const char * const ipi_names[] = {
[IPI_RESCHEDULE] = "Rescheduling interrupts",
[IPI_CALL_FUNC] = "Function call interrupts",
[IPI_CPU_STOP] = "CPU stop interrupts",
+ [IPI_CPU_CRASH_STOP] = "CPU stop (for crash dump) interrupts",
[IPI_IRQ_WORK] = "IRQ work interrupts",
[IPI_TIMER] = "Timer broadcast interrupts",
};
@@ -235,6 +270,64 @@ void smp_send_stop(void)
cpumask_pr_args(cpu_online_mask));
}
+#ifdef CONFIG_KEXEC_CORE
+/*
+ * The number of CPUs online, not counting this CPU (which may not be
+ * fully online and so not counted in num_online_cpus()).
+ */
+static inline unsigned int num_other_online_cpus(void)
+{
+ unsigned int this_cpu_online = cpu_online(smp_processor_id());
+
+ return num_online_cpus() - this_cpu_online;
+}
+
+void crash_smp_send_stop(void)
+{
+ 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 this cpu is the only one alive at this point in time, online or
+ * not, there are no stop messages to be sent around, so just back out.
+ */
+ if (num_other_online_cpus() == 0)
+ return;
+
+ cpumask_copy(&mask, cpu_online_mask);
+ cpumask_clear_cpu(smp_processor_id(), &mask);
+
+ atomic_set(&waiting_for_crash_ipi, num_other_online_cpus());
+
+ pr_crit("SMP: stopping secondary CPUs\n");
+ send_ipi_mask(&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));
+}
+
+bool smp_crash_stop_failed(void)
+{
+ return (atomic_read(&waiting_for_crash_ipi) > 0);
+}
+#endif
+
void smp_send_reschedule(int cpu)
{
send_ipi_single(cpu, IPI_RESCHEDULE);
--
2.36.1
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