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Commit 2bc5c282 authored by Russ Anderson's avatar Russ Anderson Committed by Tony Luck
Browse files

[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: default avatarRuss Anderson <rja@sgi.com>
Signed-off-by: default avatarTony 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 @@ ia64_mca_modify_original_stack(struct pt_regs *regs, 
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(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.

	 */