[PATCH 1/2] powerpc/kexec: Add to and tidy debug/comments in machine_kexec64.c

Matt Evans
2010-07-30T04:47:12Z

Tidies some typos, KERN_INFO-ise an info msg, and add a debug msg showing
when the final sequence starts.

Also adds a comment to kexec_prepare_cpus_wait() to make note of a possible
problem; the need for kexec to deal with CPUs that failed to originally start
up.

Signed-off-by: Matt Evans <matt@ozlabs.org>
---
arch/powerpc/kernel/machine_kexec_64.c | 29 ++++++++++++++++++++++++-----
1 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kernel/machine_kexec_64.c b/arch/powerpc/kernel/machine_kexec_64.c
index 4fbb3be..aa3d5cd 100644
--- a/arch/powerpc/kernel/machine_kexec_64.c
+++ b/arch/powerpc/kernel/machine_kexec_64.c
@@ -15,6 +15,7 @@
#include <linux/thread_info.h>
#include <linux/init_task.h>
#include <linux/errno.h>
+#include <linux/kernel.h>

#include <asm/page.h>
#include <asm/current.h>
@@ -181,7 +182,20 @@ static void kexec_prepare_cpus_wait(int wait_state)
int my_cpu, i, notified=-1;

my_cpu = get_cpu();
- /* Make sure each CPU has atleast made it to the state we need */
+ /* Make sure each CPU has at least made it to the state we need.
+ *
+ * FIXME: There is a (slim) chance of a problem if not all of the CPUs
+ * are correctly onlined. If somehow we start a CPU on boot with RTAS
+ * start-cpu, but somehow that CPU doesn't write callin_cpu_map[] in
+ * time, the boot CPU will timeout. If it does eventually execute
+ * stuff, the secondary will start up (paca[].cpu_start was written) and
+ * get into a peculiar state. If the platform supports
+ * smp_ops->take_timebase(), the secondary CPU will probably be spinning
+ * in there. If not (i.e. pseries), the secondary will continue on and
+ * try to online itself/idle/etc. If it survives that, we need to find
+ * these possible-but-not-online-but-should-be CPUs and chaperone them
+ * into kexec_smp_wait().
+ */
for_each_online_cpu(i) {
if (i == my_cpu)
continue;
@@ -189,9 +203,9 @@ static void kexec_prepare_cpus_wait(int wait_state)
while (paca[i].kexec_state < wait_state) {
barrier();
if (i != notified) {
- printk( "kexec: waiting for cpu %d (physical"
- " %d) to enter %i state\n",
- i, paca[i].hw_cpu_id, wait_state);
+ printk(KERN_INFO "kexec: waiting for cpu %d "
+ "(physical %d) to enter %i state\n",
+ i, paca[i].hw_cpu_id, wait_state);
notified = i;
}
}
@@ -215,7 +229,10 @@ static void kexec_prepare_cpus(void)
if (ppc_md.kexec_cpu_down)
ppc_md.kexec_cpu_down(0, 0);

- /* Before removing MMU mapings make sure all CPUs have entered real mode */
+ /*
+ * Before removing MMU mappings make sure all CPUs have entered real
+ * mode:
+ */
kexec_prepare_cpus_wait(KEXEC_STATE_REAL_MODE);

put_cpu();
@@ -284,6 +301,8 @@ void default_machine_kexec(struct kimage *image)
if (crashing_cpu == -1)
kexec_prepare_cpus();

+ pr_debug("kexec: Starting switchover sequence.\n");
+
/* switch to a staticly allocated stack. Based on irq stack code.
* XXX: the task struct will likely be invalid once we do the copy!
*/
--
1.6.3.3