[Xen-changelog] [xen-unstable] [XEN][POWERPC] Fix IPI stall timeout without using timebase_freq

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Jimi Xenidis <jimix@xxxxxxxxxxxxxx>
# Node ID 5a3fd0b7617dc9ad1664ec960efdfa22bae83a78
# Parent  4a27df713c66935d0df5f9ef67b57dc8cfb54602
[XEN][POWERPC] Fix IPI stall timeout without using timebase_freq
When using the register dump feature of Xen, one will sometimes see a
message about an IPI finish stall.  This is because of an int to long
comparison bug, so fix it by doing proper nanosecond based time
accounting with no explicit reference to timebase_freq.
Signed-off-by: Amos Waterland <apw@xxxxxxxxxx>
Signed-off-by: Jimi Xenidis <jimix@xxxxxxxxxxxxxx>
Signed-off-by: Hollis Blanchard <hollisb@xxxxxxxxxx>
---
 xen/arch/powerpc/smp.c |   39 +++++++++++++++++++++++++--------------
 1 files changed, 25 insertions(+), 14 deletions(-)

diff -r 4a27df713c66 -r 5a3fd0b7617d xen/arch/powerpc/smp.c
--- a/xen/arch/powerpc/smp.c    Tue Nov 28 17:01:00 2006 -0500
+++ b/xen/arch/powerpc/smp.c    Tue Nov 28 18:46:13 2006 -0500
@@ -90,7 +90,8 @@ int on_selected_cpus(
     int retry,
     int wait)
 {
-    int t, retval = 0, nr_cpus = cpus_weight(selected);
+    int retval = 0, nr_cpus = cpus_weight(selected);
+    unsigned long start, stall = SECONDS(1);
 
     spin_lock(&call_lock);
 
@@ -104,19 +105,21 @@ int on_selected_cpus(
     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) {
+    for (start = NOW(); atomic_read(&call_data.started) != nr_cpus; ) {
+        if (NOW() > start + stall) {
             printk("IPI start stall: %d ACKS to %d SYNS\n", 
                    atomic_read(&call_data.started), nr_cpus);
+           start = NOW();
         }
     }
 
     /* 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) {
+        for (start = NOW(); atomic_read(&call_data.finished) != nr_cpus; ) {
+            if (NOW() > start + stall) {
                 printk("IPI finish stall: %d ACKS to %d SYNS\n", 
                        atomic_read(&call_data.finished), nr_cpus);
+                start = NOW();
             }
         }
     }
@@ -168,6 +171,11 @@ void smp_message_recv(int msg, struct cp
 #ifdef DEBUG_IPI
 static void debug_ipi_ack(void *info)
 {
+    if (info) {
+       unsigned long start, stall = SECONDS(5);
+       for (start = NOW(); NOW() < start + stall; );
+       printk("IPI recv on cpu #%d: %s\n", smp_processor_id(), (char *)info);
+    }
     return;
 }
 
@@ -175,12 +183,12 @@ void ipi_torture_test(void)
 {
     int cpu;
     unsigned long before, after, delta;
-    unsigned long min = ~0, max = 0, mean = 0, sum = 0, tick = 0;
+    unsigned long min = ~0, max = 0, mean = 0, sum = 0, trials = 0;
     cpumask_t mask;
 
     cpus_clear(mask);
 
-    while (tick < 1000000) {
+    while (trials < 1000000) {
         for_each_online_cpu(cpu) {
             cpu_set(cpu, mask);
             before = mftb();
@@ -192,12 +200,15 @@ void ipi_torture_test(void)
             if (delta > max) max = delta;
             if (delta < min) min = delta;
             sum += delta;
-            tick++;
-        }
-    }
-
-    mean = sum / tick;
-
-    printk("IPI tb ticks: min = %ld max = %ld mean = %ld\n", min, max, mean);
+            trials++;
+        }
+    }
+
+    mean = tb_to_ns(sum / trials);
+
+    printk("IPI latency: min = %ld ticks, max = %ld ticks, mean = %ldns\n",
+          min, max, mean);
+
+    smp_call_function(debug_ipi_ack, "Hi", 0, 1);
 }
 #endif

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-changelog