Tue Dec 17 22:39:49 2013 UTC ()

Pull up following revision(s) (requested by bouyer in ticket #995):
	sys/arch/xen/xen/evtchn.c: revision 1.70
Remove the "evtchn_do_event: handler %p didn't lower ipl %d %d\n" printf.
With help from Robert Elz we've finally figured out what's going on, and
it actually isn't a bug in the handler, but related to spin mutexes.
When a spin mutex is released, the IPL isn't lowered back if the
curcpu is holding other spin mutexes. This is because mutexes may not
be released in order (and, in this case, the CPU in interrupted while
it holds a spin mutex at IPL < IPL_SCHED).
Also remove the test and resetting the IPL, it will be reset anyway
inside the loop, or at the end of the loop.


(riz)

diff -r1.62 -r1.62.8.1 src/sys/arch/xen/xen/evtchn.c

--- src/sys/arch/xen/xen/evtchn.c 2012/02/12 14:24:08	1.62
+++ src/sys/arch/xen/xen/evtchn.c 2013/12/17 22:39:49	1.62.8.1

 @@ -1,14 +1,14 @@
-/*	$NetBSD: evtchn.c,v 1.62 2012/02/12 14:24:08 jym Exp $	*/
+/*	$NetBSD: evtchn.c,v 1.62.8.1 2013/12/17 22:39:49 riz Exp $	*/
 /*
  * Copyright (c) 2006 Manuel Bouyer.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
+ *
 @@ -44,27 +44,27 @@
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: evtchn.c,v 1.62 2012/02/12 14:24:08 jym Exp $");
+__KERNEL_RCSID(0, "$NetBSD: evtchn.c,v 1.62.8.1 2013/12/17 22:39:49 riz Exp $");
 #include "opt_xen.h"
 #include "isa.h"
 #include "pci.h"
 #include <sys/param.h>
 #include <sys/cpu.h>
 #include <sys/kernel.h>
 #include <sys/systm.h>
 #include <sys/device.h>
 #include <sys/proc.h>
 #include <sys/kmem.h>
 #include <sys/reboot.h>
 @@ -337,33 +337,26 @@ splx:
 		iplbit = 1 << (NIPL - 1);
 		i = (NIPL - 1);
 		while (iplmask != 0 && i > ilevel) {
 			while (iplmask & iplbit) {
 				ci->ci_ipending &= ~iplbit;
 				ci->ci_ilevel = i;
 				for (ih = ci->ci_isources[i]->ipl_handlers;
 				    ih != NULL; ih = ih->ih_ipl_next) {
 					KASSERT(ih->ih_cpu == ci);
 					sti();
 					ih_fun = (void *)ih->ih_fun;
 					ih_fun(ih->ih_arg, regs);
 					cli();
 					if (ci->ci_ilevel != i) {
 						printf("evtchn_do_event: "
 						    "handler %p didn't lower "
 						    "ipl %d %d\n",
 						    ih_fun, ci->ci_ilevel, i);
 						ci->ci_ilevel = i;
+				}
 				hypervisor_enable_ipl(i);
 				/* more pending IPLs may have been registered */
 				iplmask =
 				    (IUNMASK(ci, ilevel) & ci->ci_ipending);
+			}
 			i--;
 			iplbit >>= 1;
+		}
+	}
 	ci->ci_ilevel = ilevel;
 	return 0;
+}