[patch] Remove needless delay in MCA rendezvous
While testing the MCA recovery code, noticed that some machines would have a
five second delay rendezvousing cpus. What was happening is that
ia64_wait_for_slaves() would check to see if all the slave CPUs had
rendezvoused. If any had not, it would wait 1 millisecond then check again.
If any CPUs had still not rendezvoused, it would wait 5 seconds before
checking again.
On some configs the rendezvous takes more than 1 millisecond, causing the code
to wait the full 5 seconds, even though the last CPU rendezvoused after only
a few milliseconds.
The fix is to check every 1 millisecond to see if all the cpus have
rendezvoused. After 5 seconds the code concludes the CPUs will never
rendezvous (same as before).
The MCA code is, by definition, not performance critical, but a needless
delay of 5 seconds is senseless. The 5 seconds also adds up quickly
when running the error injection code in a loop.
This patch both simplifies the code and removes the needless delay.
Signed-off-by: Russ Anderson <rja@xxxxxxx>
---
arch/ia64/kernel/mca.c | 41 +++++++++++++++++++----------------------
1 file changed, 19 insertions(+), 22 deletions(-)
Index: test/arch/ia64/kernel/mca.c
===================================================================
--- test.orig/arch/ia64/kernel/mca.c 2007-09-20 10:23:57.011455209 -0500
+++ test/arch/ia64/kernel/mca.c 2007-09-20 10:24:00.463872304 -0500
@@ -1136,30 +1136,27 @@ no_mod:
static void
ia64_wait_for_slaves(int monarch, const char *type)
{
- int c, wait = 0, missing = 0;
- for_each_online_cpu(c) {
- if (c == monarch)
- continue;
- if (ia64_mc_info.imi_rendez_checkin[c] == IA64_MCA_RENDEZ_CHECKIN_NOTDONE) {
- udelay(1000); /* short wait first */
- wait = 1;
- break;
+ int c, i , wait;
+
+ /*
+ * wait 5 seconds total for slaves (arbitrary)
+ */
+ for (i = 0; i < 5000; i++) {
+ wait = 0;
+ for_each_online_cpu(c) {
+ if (c == monarch)
+ continue;
+ if (ia64_mc_info.imi_rendez_checkin[c]
+ == IA64_MCA_RENDEZ_CHECKIN_NOTDONE) {
+ udelay(1000); /* short wait */
+ wait = 1;
+ break;
+ }
}
+ if (!wait)
+ goto all_in;
}
- if (!wait)
- goto all_in;
- for_each_online_cpu(c) {
- if (c == monarch)
- continue;
- if (ia64_mc_info.imi_rendez_checkin[c] == IA64_MCA_RENDEZ_CHECKIN_NOTDONE) {
- udelay(5*1000000); /* wait 5 seconds for slaves (arbitrary) */
- if (ia64_mc_info.imi_rendez_checkin[c] == IA64_MCA_RENDEZ_CHECKIN_NOTDONE)
- missing = 1;
- break;
- }
- }
- if (!missing)
- goto all_in;
+
/*
* Maybe slave(s) dead. Print buffered messages immediately.
*/
--
Russ Anderson RAS group SGI rja@xxxxxxx
-
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