svn commit: r288447 - in head/sys/arm: broadcom/bcm2835 mv

[Andrew Turner]

Author: andrew
Date: Thu Oct  1 12:09:05 2015
New Revision: 288447
URL: https://svnweb.freebsd.org/changeset/base/288447

Log:
  An IPI must be cleared before it is handled otherwise next IPI could be
  missed. In other words, if a new request for an IPI is sent while the
  previous request is being handled but the IPI is not cleared yet, the
  clearing of the previous IPI request also clears the new one and the
  handling is missed.
  
  There are only three MP interrupt controllers in ARM now. Two of them are
  fixed by this change, the third one is correct, probably only just by
  accident. The fix is minimalistic as new interrupt framework is awaited.
  
  It was debugged on RPi2 where missing IPI handling together with SCHED_ULE
  led to situation in which tdq_ipipending was not cleared and so IPI_PREEMPT
  was stopped to be sent. Various odditys were found related to slow system
  response time like various events timed out, and slow console response.
  
  Submitted by:	Svatopluk Kraus <onwahe at gmail.com>
  Reviewed by:	loos, kib
  MFC after:	1 week
  Differential Revision:	https://reviews.freebsd.org/D3722

Modified:
  head/sys/arm/broadcom/bcm2835/bcm2836_mp.c
  head/sys/arm/mv/mpic.c

Modified: head/sys/arm/broadcom/bcm2835/bcm2836_mp.c
==============================================================================
--- head/sys/arm/broadcom/bcm2835/bcm2836_mp.c	Thu Oct  1 10:52:26 2015	(r288446)
+++ head/sys/arm/broadcom/bcm2835/bcm2836_mp.c	Thu Oct  1 12:09:05 2015	(r288447)
@@ -182,6 +182,8 @@ pic_ipi_read(int i)
 		if (val == 0)
 			return (0);
 		ipi = ffs(val) - 1;
+		BSWR4(MBOX0CLR_CORE(cpu), 1 << ipi);
+		dsb();
 		return (ipi);
 	}
 	return (0x3ff);
@@ -190,12 +192,6 @@ pic_ipi_read(int i)
 void
 pic_ipi_clear(int ipi)
 {
-	int cpu;
-
-	cpu = PCPU_GET(cpuid);
-	dsb();
-	BSWR4(MBOX0CLR_CORE(cpu), 1 << ipi);
-	wmb();
 }
 
 void

Modified: head/sys/arm/mv/mpic.c
==============================================================================
--- head/sys/arm/mv/mpic.c	Thu Oct  1 10:52:26 2015	(r288446)
+++ head/sys/arm/mv/mpic.c	Thu Oct  1 12:09:05 2015	(r288447)
@@ -378,10 +378,14 @@ int
 pic_ipi_read(int i __unused)
 {
 	uint32_t val;
+	int ipi;
 
 	val = MPIC_CPU_READ(mv_mpic_sc, MPIC_IN_DRBL);
-	if (val)
-		return (ffs(val) - 1);
+	if (val) {
+		ipi = ffs(val) - 1;
+		MPIC_CPU_WRITE(mv_mpic_sc, MPIC_IN_DRBL, ~(1 << ipi));
+		return (ipi);
+	}
 
 	return (0x3ff);
 }
@@ -389,10 +393,6 @@ pic_ipi_read(int i __unused)
 void
 pic_ipi_clear(int ipi)
 {
-	uint32_t val;
-
-	val = ~(1 << ipi);
-	MPIC_CPU_WRITE(mv_mpic_sc, MPIC_IN_DRBL, val);
 }
 
 #endif