[PATCH 7/7] ia64, kdump: Short path to freeze CPUs

[Hidetoshi Seto]

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 at jp.fujitsu.com>
Cc: Vivek Goyal <vgoyal at redhat.com>
Cc: Haren Myneni <hbabu at us.ibm.com>
Cc: kexec at lists.infradead.org
---
 arch/ia64/kernel/crash.c |   15 ++++++---------
 arch/ia64/kernel/mca.c   |   15 +++++++++++++--
 2 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/arch/ia64/kernel/crash.c b/arch/ia64/kernel/crash.c
index f43eccf..cf833af 100644
--- a/arch/ia64/kernel/crash.c
+++ b/arch/ia64/kernel/crash.c
@@ -129,14 +129,13 @@ 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 */
@@ -189,6 +188,7 @@ 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;
@@ -219,7 +219,6 @@ 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:
@@ -230,10 +229,8 @@ 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 8f33a88..7a34c6c 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);
 
-- 
1.6.0