powerpc/kdump: Only save CPU state first time through the secondary CPU capture code

We might enter the secondary CPU capture code twice, eg if we have to
unstick some CPUs with a system reset. In this case we don't want to
overwrite the state on CPUs that had made it into the capture code OK,
so use the cpus_state_saved cpumask for that and make it local to
crash_ipi_callback.

For controlling progress now use atomic_t cpus_in_crash to count how
many CPUs have made it into the kdump code, and time_to_dump to tell
everyone it's time to dump.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 21 insertions, 12 deletions

diff --git a/arch/powerpc/kernel/crash.c b/arch/powerpc/kernel/crash.c
index b942980e9650..28be3452e67a 100644
--- a/arch/powerpc/kernel/crash.c
+++ b/arch/powerpc/kernel/crash.c
@@ -46,7 +46,8 @@
 
 /* This keeps a track of which one is the crashing cpu. */
 int crashing_cpu = -1;
-static cpumask_t cpus_in_crash = CPU_MASK_NONE;
+static atomic_t cpus_in_crash;
+static int time_to_dump;
 
 #define CRASH_HANDLER_MAX 3
 /* NULL terminated list of shutdown handles */
@@ -67,21 +68,27 @@ static int handle_fault(struct pt_regs *regs)
 
 void crash_ipi_callback(struct pt_regs *regs)
 {
+        static cpumask_t cpus_state_saved = CPU_MASK_NONE;
+
         int cpu = smp_processor_id();
 
         if (!cpu_online(cpu))
                 return;
 
         hard_irq_disable();
-        if (!cpumask_test_cpu(cpu, &cpus_in_crash))
+        if (!cpumask_test_cpu(cpu, &cpus_state_saved)) {
                 crash_save_cpu(regs, cpu);
-        cpumask_set_cpu(cpu, &cpus_in_crash);
+                cpumask_set_cpu(cpu, &cpus_state_saved);
+        }
+
+        atomic_inc(&cpus_in_crash);
+        smp_mb__after_atomic_inc();
 
         /*
          * Starting the kdump boot.
          * This barrier is needed to make sure that all CPUs are stopped.
          */
-        while (!cpumask_test_cpu(crashing_cpu, &cpus_in_crash))
+        while (!time_to_dump)
                 cpu_relax();
 
         if (ppc_md.kexec_cpu_down)
@@ -115,19 +122,18 @@ again:
          * respond.
          */
         msecs = IPI_TIMEOUT;
-        while ((cpumask_weight(&cpus_in_crash) < ncpus) && (--msecs > 0)) {
+        while ((atomic_read(&cpus_in_crash) < ncpus) && (--msecs > 0))
                 mdelay(1);
-        }
 
         /* Would it be better to replace the trap vector here? */
 
-        if (cpumask_weight(&cpus_in_crash) >= ncpus) {
+        if (atomic_read(&cpus_in_crash) >= ncpus) {
                 printk(KERN_EMERG "IPI complete\n");
                 return;
         }
 
         printk(KERN_EMERG "ERROR: %d cpu(s) not responding\n",
-                ncpus - cpumask_weight(&cpus_in_crash));
+                ncpus - atomic_read(&cpus_in_crash));
 
         /*
          * If we have a panic timeout set then we can't wait indefinitely
@@ -155,10 +161,10 @@ again:
                  * crash code again. We need to reset cpus_in_crash so we
                  * wait for everyone to do this.
                  */
-                cpus_in_crash = CPU_MASK_NONE;
+                atomic_set(&cpus_in_crash, 0);
                 smp_mb();
 
-                while (cpumask_weight(&cpus_in_crash) < ncpus)
+                while (atomic_read(&cpus_in_crash) < ncpus)
                         cpu_relax();
         }
 
@@ -316,7 +322,6 @@ void default_machine_crash_shutdown(struct pt_regs *regs)
          * such that another IPI will not be sent.
          */
         crashing_cpu = smp_processor_id();
-        crash_save_cpu(regs, crashing_cpu);
 
         /*
          * If we came in via system reset, wait a while for the secondary
@@ -326,7 +331,11 @@ void default_machine_crash_shutdown(struct pt_regs *regs)
                 mdelay(PRIMARY_TIMEOUT);
 
         crash_kexec_prepare_cpus(crashing_cpu);
-        cpumask_set_cpu(crashing_cpu, &cpus_in_crash);
+
+        crash_save_cpu(regs, crashing_cpu);
+
+        time_to_dump = 1;
+
         crash_kexec_wait_realmode(crashing_cpu);
 
         machine_kexec_mask_interrupts();