fix timer interrupts getting lost

This patch fixes the issue of some CPUs not showing timer interrupts
going off. Seems during the process of sync'ing the itc, we jumped over the next timer value. This patch is against 2.5.67 + ia64. I haven't seen the problem on 2.4, but a quick looks seems like it's potentially an issue there too. Thanks,

Alex

--
Alex Williamson HP Linux and Open Source Lab

@@ -311,6 +311,15 @@
 		 */
 		Dprintk("Going to syncup ITC with BP.\n");
 		ia64_sync_itc(0);
+
+		/*
+		 * Make sure we didn't sync the itc ahead of the next
+		 * timer interrupt, if so, just reset it.
+		 */
+		if (time_after(ia64_get_itc(),local_cpu_data->itm_next)) {
+			Dprintk("oops, jumped a timer.\n");
+			ia64_cpu_local_tick();
+		}
 	}
 
 	/*

Thanks Alex!

This patch fixed the problem I reported before. And I could observe some "oops jumped a timer." messages (with debug flag enabled).

Thanks,
---
Takayoshi Kochi <[email protected]>

Alex> This patch fixes the issue of some CPUs not showing timer Alex> interrupts going off. Seems during the process of sync'ing Alex> the itc, we jumped over the next timer value. This patch is Alex> against 2.5.67 + ia64. I haven't seen the problem on 2.4, but Alex> a quick looks seems like it's potentially an issue there too. Alex> Thanks,

Good catch. I applied this patch now.

The reason it started to show up on 2.5 now is mostly likely because I had to move the ITC syncing to a point where interrupts are enabled.

	--david

I applied this for 2.4 also. Thanks!