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From: Nathan Whitehorn <nwhitehorn@FreeBSD.org>
Date: Wed, 24 Aug 2016 16:49:14 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r304756 - head/sys/powerpc/pseries
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Author: nwhitehorn
Date: Wed Aug 24 16:49:14 2016
New Revision: 304756
URL: https://svnweb.freebsd.org/changeset/base/304756

Log:
  Close a race when making the CPU idle under pHyp. If an interrupt occurs
  between the beginning of the idle function and actually going idle, the
  CPU could go to sleep with pending work.
  
  MFC after:	1 month

Modified:
  head/sys/powerpc/pseries/platform_chrp.c

Modified: head/sys/powerpc/pseries/platform_chrp.c
==============================================================================
--- head/sys/powerpc/pseries/platform_chrp.c	Wed Aug 24 16:44:27 2016	(r304755)
+++ head/sys/powerpc/pseries/platform_chrp.c	Wed Aug 24 16:49:14 2016	(r304756)
@@ -34,6 +34,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/bus.h>
 #include <sys/pcpu.h>
 #include <sys/proc.h>
+#include <sys/sched.h>
 #include <sys/smp.h>
 #include <vm/vm.h>
 #include <vm/pmap.h>
@@ -492,7 +493,18 @@ chrp_reset(platform_t platform)
 static void
 phyp_cpu_idle(sbintime_t sbt)
 {
-	phyp_hcall(H_CEDE);
+	register_t msr;
+
+	msr = mfmsr();
+
+	mtmsr(msr & ~PSL_EE);
+	if (sched_runnable()) {
+		mtmsr(msr);
+		return;
+	}
+
+	phyp_hcall(H_CEDE); /* Re-enables interrupts internally */
+	mtmsr(msr);
 }
 
 static void