Commit 2bc5c282 authored Sep 20, 2007 by Russ Anderson Committed by Tony Luck Oct 12, 2007

[IA64] 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@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

parent 28eda5b8

arch/ia64/kernel/mca.c

+19 −22

Original line number	Diff line number	Diff line
		@@ -1135,30 +1135,27 @@ no_mod:
		static void
		ia64_wait_for_slaves(int monarch, const char *type)
		{
		int c, wait = 0, missing = 0;
		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 first */
		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;
		for_each_online_cpu(c) {
		if (c == monarch)
		continue;
		if (ia64_mc_info.imi_rendez_checkin[c] == IA64_MCA_RENDEZ_CHECKIN_NOTDONE) {
		udelay(51000000); / 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.
		*/

Admin message