On Nov 28, 2006, at 1:37 AM, Amos Waterland wrote:
This will have to be reworked and broken up into individual parts for
submission, but here is what is necessary to make 'C-a C-a C-a t' work
properly.
Jimi, when you disassemble xen-syms compiled without this patch, do
you
see a bogus infinite loop in read_clocks?
looked briefly but did not notice it.
The compiler is not told that
read_clocks_cpumask is volatile, so it is free to turn that loop
into an
infinite loop, as my gcc 4.1.1 cross-compiler does. I am surprised
that
other Xen architectures have not seen the same problem.
Found it, cpu_relax() is supposed to contain barrier() call.
My fault but it coulda been hollis :)
diff -r cc45282daf3d xen/include/asm-powerpc/processor.h
--- a/xen/include/asm-powerpc/processor.h Mon Nov 27 17:17:07 2006 -0500
+++ b/xen/include/asm-powerpc/processor.h Tue Nov 28 10:19:09 2006 -0500
@@ -152,7 +152,7 @@ static inline void nop(void) {
static inline void nop(void) {
__asm__ __volatile__ ("nop");
}
-#define cpu_relax() nop()
+#define cpu_relax() barrier()
static inline unsigned int mfpir(void)
{
this will solve the volatile issue and am pushing this now.
more below..
arch/powerpc/smp.c | 18 ++++++++++--------
common/keyhandler.c | 2 +-
include/xen/cpumask.h | 2 +-
3 files changed, 12 insertions(+), 10 deletions(-)
diff -r 305751a5281e xen/arch/powerpc/smp.c
--- a/xen/arch/powerpc/smp.c Wed Nov 22 16:29:25 2006 -0500
+++ b/xen/arch/powerpc/smp.c Tue Nov 28 00:45:24 2006 -0500
@@ -91,31 +91,33 @@ int on_selected_cpus(
int wait)
{
int t, retval = 0, nr_cpus = cpus_weight(selected);
+ int stall = timebase_freq * 10;
spin_lock(&call_lock);
call_data.func = func;
call_data.info = info;
call_data.wait = wait;
- call_data.wait = 1; /* Until we get RCU around call_data. */
atomic_set(&call_data.started, 0);
atomic_set(&call_data.finished, 0);
mb();
send_IPI_mask(selected, CALL_FUNCTION_VECTOR);
- /* We always wait for an initiation ACK from remote CPU. */
- for (t = 0; atomic_read(&call_data.started) != nr_cpus; t++) {
- if (t && t % timebase_freq == 0) {
- printk("IPI start stall: %d ACKS to %d SYNS\n",
- atomic_read(&call_data.started), nr_cpus);
- }
+ /* If told to, we wait for an initiation ACK from remote CPU. */
+ if (wait) {
+ for (t = 0; atomic_read(&call_data.started) != nr_cpus; t++) {
+ if (t > 0 && t % stall == 0) {
+ printk("IPI start stall: %d ACKS to %d SYNS\n",
+ atomic_read(&call_data.started), nr_cpus);
+ }
+ }
you _always_ have to wait for call_data.started it means that its
safe to reuse call_data.
}
/* If told to, we wait for a completion ACK from remote CPU. */
if (wait) {
for (t = 0; atomic_read(&call_data.finished) != nr_cpus; t+
+) {
- if (t > timebase_freq && t % timebase_freq == 0) {
+ if (t > 0 && t % stall == 0) {
printk("IPI finish stall: %d ACKS to %d SYNS\n",
atomic_read(&call_data.finished), nr_cpus);
}
diff -r 305751a5281e xen/common/keyhandler.c
--- a/xen/common/keyhandler.c Wed Nov 22 16:29:25 2006 -0500
+++ b/xen/common/keyhandler.c Tue Nov 28 00:12:14 2006 -0500
@@ -193,7 +193,7 @@ static void dump_domains(unsigned char k
read_unlock(&domlist_lock);
}
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