[IA64] kdump: Short path to freeze CPUs

Setting monarch_cpu = -1 to let slaves frozen might not work, because
there might be slaves being late, not entered the rendezvous yet.
Such slaves might be caught in while (monarch_cpu == -1) loop.

Use kdump_in_progress instead of monarch_cpus to break INIT rendezvous
and let all slaves enter DIE_INIT_SLAVE_LEAVE smoothly.

And monarch no longer need to manage rendezvous if once kdump_in_progress
is set, catch the monarch in DIE_INIT_MONARCH_ENTER then.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Haren Myneni <hbabu@us.ibm.com>
Cc: kexec@lists.infradead.org
Acked-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

2 files changed, 19 insertions, 11 deletions

diff --git a/arch/ia64/kernel/crash.c b/arch/ia64/kernel/crash.c
index 0995fdc7b299..6631a9dfafdc 100644
--- a/arch/ia64/kernel/crash.c
+++ b/arch/ia64/kernel/crash.c
@@ -127,14 +127,13 @@ machine_crash_shutdown(struct pt_regs *pt)
          * If an INIT is asserted here:
          * - All receivers might be slaves, since some of cpus could already
          *   be frozen and INIT might be masked on monarch.  In this case,
-         *   all slaves will park in while (monarch_cpu == -1) loop before
-         *   DIE_INIT_SLAVE_ENTER that for waiting monarch enters.
-         *      => TBD: freeze all slaves
+         *   all slaves will be frozen soon since kdump_in_progress will let
+         *   them into DIE_INIT_SLAVE_LEAVE.
          * - One might be a monarch, but INIT rendezvous will fail since
          *   at least this cpu already have INIT masked so it never join
          *   to the rendezvous.  In this case, all slaves and monarch will
-         *   be frozen after timeout of the INIT rendezvous.
-         *      => TBD: freeze them without waiting timeout
+         *   be frozen soon with no wait since the INIT rendezvous is skipped
+         *   by kdump_in_progress.
          */
         kdump_smp_send_stop();
         /* not all cpu response to IPI, send INIT to freeze them */
@@ -187,6 +186,7 @@ kdump_init_notifier(struct notifier_block *self, unsigned long val, void *data)
                                 break;
                         /* fall through */
                 case DIE_INIT_SLAVE_LEAVE:
+                case DIE_INIT_MONARCH_ENTER:
                 case DIE_MCA_RENDZVOUS_LEAVE:
                         unw_init_running(kdump_cpu_freeze, NULL);
                         break;
@@ -217,7 +217,6 @@ kdump_init_notifier(struct notifier_block *self, unsigned long val, void *data)
                 if (kdump_on_init && (nd->sos->rv_rc != 1)) {
                         if (atomic_inc_return(&kdump_in_progress) != 1)
                                 kdump_freeze_monarch = 1;
-                        *(nd->monarch_cpu) = -1;
                 }
                 break;
         case DIE_INIT_MONARCH_LEAVE:
@@ -228,10 +227,8 @@ kdump_init_notifier(struct notifier_block *self, unsigned long val, void *data)
         case DIE_MCA_MONARCH_LEAVE:
                 /* *(nd->data) indicate if MCA is recoverable */
                 if (kdump_on_fatal_mca && !(*(nd->data))) {
-                        if (atomic_inc_return(&kdump_in_progress) == 1) {
-                                *(nd->monarch_cpu) = -1;
+                        if (atomic_inc_return(&kdump_in_progress) == 1)
                                 machine_kdump_on_init();
-                        }
                         /* We got fatal MCA while kdump!? No way!! */
                 }
                 break;
diff --git a/arch/ia64/kernel/mca.c b/arch/ia64/kernel/mca.c
index 7b30d21c5190..d2877a7bfe2e 100644
--- a/arch/ia64/kernel/mca.c
+++ b/arch/ia64/kernel/mca.c
@@ -1682,14 +1682,25 @@ ia64_init_handler(struct pt_regs *regs, struct switch_stack *sw,
 
         if (!sos->monarch) {
                 ia64_mc_info.imi_rendez_checkin[cpu] = IA64_MCA_RENDEZ_CHECKIN_INIT;
+
+#ifdef CONFIG_KEXEC
+                while (monarch_cpu == -1 && !atomic_read(&kdump_in_progress))
+                        udelay(1000);
+#else
                 while (monarch_cpu == -1)
-                       cpu_relax();     /* spin until monarch enters */
+                        cpu_relax();    /* spin until monarch enters */
+#endif
 
                 NOTIFY_INIT(DIE_INIT_SLAVE_ENTER, regs, (long)&nd, 1);
                 NOTIFY_INIT(DIE_INIT_SLAVE_PROCESS, regs, (long)&nd, 1);
 
+#ifdef CONFIG_KEXEC
+                while (monarch_cpu != -1 && !atomic_read(&kdump_in_progress))
+                        udelay(1000);
+#else
                 while (monarch_cpu != -1)
-                       cpu_relax();     /* spin until monarch leaves */
+                        cpu_relax();    /* spin until monarch leaves */
+#endif
 
                 NOTIFY_INIT(DIE_INIT_SLAVE_LEAVE, regs, (long)&nd, 1);