riscv: don't stop itself in smp_send_stop

Add IPI_CPU_STOP message and use it in smp_send_stop to stop other cpus,
but not itself.  Mark cpu offline on reception of IPI_CPU_STOP.

Signed-off-by: Andreas Schwab <schwab@suse.de>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index 57b1383e5ef7480142ce857e600a6f0e73a0944e..246635eac7bb5cd4652f4551007a642f37935836 100644 (file)
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -23,6 +23,7 @@
 #include <linux/smp.h>
 #include <linux/sched.h>
 #include <linux/seq_file.h>
+#include <linux/delay.h>
 
 #include <asm/sbi.h>
 #include <asm/tlbflush.h>
@@ -31,6 +32,7 @@
 enum ipi_message_type {
        IPI_RESCHEDULE,
        IPI_CALL_FUNC,
+       IPI_CPU_STOP,
        IPI_MAX
 };
 
@@ -66,6 +68,13 @@ int setup_profiling_timer(unsigned int multiplier)
        return -EINVAL;
 }
 
+static void ipi_stop(void)
+{
+       set_cpu_online(smp_processor_id(), false);
+       while (1)
+               wait_for_interrupt();
+}
+
 void riscv_software_interrupt(void)
 {
        unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;
@@ -94,6 +103,11 @@ void riscv_software_interrupt(void)
                        generic_smp_call_function_interrupt();
                }
 
+               if (ops & (1 << IPI_CPU_STOP)) {
+                       stats[IPI_CPU_STOP]++;
+                       ipi_stop();
+               }
+
                BUG_ON((ops >> IPI_MAX) != 0);
 
                /* Order data access and bit testing. */
@@ -121,6 +135,7 @@ send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation)
 static const char * const ipi_names[] = {
        [IPI_RESCHEDULE]        = "Rescheduling interrupts",
        [IPI_CALL_FUNC]         = "Function call interrupts",
+       [IPI_CPU_STOP]          = "CPU stop interrupts",
 };
 
 void show_ipi_stats(struct seq_file *p, int prec)
@@ -146,15 +161,29 @@ void arch_send_call_function_single_ipi(int cpu)
        send_ipi_message(cpumask_of(cpu), IPI_CALL_FUNC);
 }
 
-static void ipi_stop(void *unused)
-{
-       while (1)
-               wait_for_interrupt();
-}
-
 void smp_send_stop(void)
 {
-       on_each_cpu(ipi_stop, NULL, 1);
+       unsigned long timeout;
+
+       if (num_online_cpus() > 1) {
+               cpumask_t mask;
+
+               cpumask_copy(&mask, cpu_online_mask);
+               cpumask_clear_cpu(smp_processor_id(), &mask);
+
+               if (system_state <= SYSTEM_RUNNING)
+                       pr_crit("SMP: stopping secondary CPUs\n");
+               send_ipi_message(&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 %*pbl\n",
+                          cpumask_pr_args(cpu_online_mask));
 }
 
 void smp_send_reschedule(int cpu)