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From: John Baldwin <jhb@FreeBSD.org>
To: Perforce Change Reviews <perforce@freebsd.org>
Subject: PERFORCE change 60954 for review
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http://perforce.freebsd.org/chv.cgi?CH=60954

Change 60954 by jhb@jhb_slimer on 2004/09/03 14:21:38

	Revert jeff's last hack to this file and restore the previous
	behavior but in a more optimal fashion.  Previously (as in 4.x
	and 5.2) we waited to return from lapic_ipi_wait() until the
	IPI was delivered.  Jeff changed it to just return immediately
	and only wait for a short time on the next IPI.  While spinwait
	IPIs like TLB shootdowns and rendezvous ensure that the IPI is
	delivered before another one is sent, one-shot IPI's like
	roundrobin, signal, hardclock, and statclock forwards do not
	wait.  So instead, change this code to just wait as long as it
	needs to until the previous IPI is cleared.  My quad xeon can't
	do a -j4 kernel build without triggering this panic right now,
	so hopefully this will fix that.

Affected files ...

.. //depot/projects/smpng/sys/i386/i386/local_apic.c#10 edit

Differences ...

==== //depot/projects/smpng/sys/i386/i386/local_apic.c#10 (text+ko) ====

@@ -693,8 +693,8 @@
 	intr_restore(eflags);
 }
 
+#ifdef DETECT_DEADLOCK
 #define	BEFORE_SPIN	1000000
-#ifdef DETECT_DEADLOCK
 #define	AFTER_SPIN	1000
 #endif
 
@@ -725,9 +725,16 @@
 		destfield = dest;
 	}
 
+#ifdef DETECT_DEADLOCK
+	/* Check for an earlier stuck IPI. */
 	/* Wait for an earlier IPI to finish. */
 	if (!lapic_ipi_wait(BEFORE_SPIN))
 		panic("APIC: Previous IPI is stuck");
+#else
+	/* Wait for an earlier IPI to finish. */
+	if (!lapic_ipi_wait(-1))
+		panic("APIC: Previous IPI is stuck");
+#endif
 
 	lapic_ipi_raw(icrlo, destfield);