[PATCH 2/3] cpu: add a CPU_DOWN_PREPARE notifier

[Nick Piggin]

2/3

Rusty, can I do this?

Add a CPU_DOWN_PREPARE hotplug CPU notifier. This is needed so we can
dettach all sched-domains before a CPU goes down, thus we can build
domains from online cpumasks, and not have to check for the possibility
of a CPU coming up or going down.

Signed-off-by: Nick Piggin <nickpiggin@xxxxxxxxxxxx>


---

 linux-2.6-npiggin/include/linux/notifier.h |    9 +++++----
 linux-2.6-npiggin/kernel/cpu.c             |    9 +++++++++
 2 files changed, 14 insertions(+), 4 deletions(-)

diff -puN kernel/cpu.c~hotplug-cpu_down_prepare-notifier kernel/cpu.c
--- linux-2.6/kernel/cpu.c~hotplug-cpu_down_prepare-notifier	2004-09-08 22:39:28.000000000 +1000
+++ linux-2.6-npiggin/kernel/cpu.c	2004-09-08 22:39:28.000000000 +1000
@@ -119,6 +119,15 @@ int cpu_down(unsigned int cpu)
 		goto out;
 	}
 
+	err = notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
+						(void *)(long)cpu);
+	if (err == NOTIFY_BAD) {
+		printk("%s: attempt to take down CPU %u failed\n",
+				__FUNCTION__, cpu);
+		err = -EINVAL;
+		goto out;
+	}
+
 	/* Ensure that we are not runnable on dying cpu */
 	old_allowed = current->cpus_allowed;
 	tmp = CPU_MASK_ALL;
diff -puN include/linux/notifier.h~hotplug-cpu_down_prepare-notifier include/linux/notifier.h
--- linux-2.6/include/linux/notifier.h~hotplug-cpu_down_prepare-notifier	2004-09-08 22:39:28.000000000 +1000
+++ linux-2.6-npiggin/include/linux/notifier.h	2004-09-08 22:39:28.000000000 +1000
@@ -60,10 +60,11 @@ extern int notifier_call_chain(struct no
 
 #define NETLINK_URELEASE	0x0001	/* Unicast netlink socket released */
 
-#define CPU_ONLINE	0x0002 /* CPU (unsigned)v is up */
-#define CPU_UP_PREPARE	0x0003 /* CPU (unsigned)v coming up */
-#define CPU_UP_CANCELED	0x0004 /* CPU (unsigned)v NOT coming up */
-#define CPU_DEAD	0x0006 /* CPU (unsigned)v dead */
+#define CPU_ONLINE		0x0002 /* CPU (unsigned)v is up */
+#define CPU_UP_PREPARE		0x0003 /* CPU (unsigned)v coming up */
+#define CPU_UP_CANCELED		0x0004 /* CPU (unsigned)v NOT coming up */
+#define CPU_DOWN_PREPARE	0x0005 /* CPU (unsigned)v going down */
+#define CPU_DEAD		0x0006 /* CPU (unsigned)v dead */
 
 #endif /* __KERNEL__ */
 #endif /* _LINUX_NOTIFIER_H */

_