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From: Andrew Turner <andrew@FreeBSD.org>
Date: Sat, 23 May 2015 23:08:17 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r283337 - head/sys/arm/arm
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Author: andrew
Date: Sat May 23 23:08:16 2015
New Revision: 283337
URL: https://svnweb.freebsd.org/changeset/base/283337

Log:
  Fix a lock up where we enter swapper() with interrupts disabled.
  
  In smp_rendezvous_cpus we expect to wait for all cpus to enter
  smp_rendezvous_action. If we call this holding a proc lock swapper may
  attempt to also lock it, however as interrupts are disabled the cpu never
  handles the ipi. Because smp_rendezvous_action waits for all signaled
  cpus before contining it may get caught waiting for the cpu running swapper
  as the proc mutex will be unlocked after smp_rendezvous_cpus finishes.
  
  The fix is to enable interrupts in the configure stage as we should be
  doing.
  
  MFC after:	1 week

Modified:
  head/sys/arm/arm/autoconf.c

Modified: head/sys/arm/arm/autoconf.c
==============================================================================
--- head/sys/arm/arm/autoconf.c	Sat May 23 23:05:31 2015	(r283336)
+++ head/sys/arm/arm/autoconf.c	Sat May 23 23:08:16 2015	(r283337)
@@ -94,6 +94,7 @@ static void
 configure_final(void *dummy)
 {
 
+	enable_interrupts(PSR_I | PSR_F);
 	cninit_finish();
 	cold = 0;
 }