From: Brad Peters <bpeters@redhat.com>
Date: Fri, 29 Feb 2008 16:13:00 -0500
Subject: [ppc64] cell: remove SPU_CONTEXT_SWITCH_ACTIVE flag
Message-id: 47C8755C.9020708@redhat.com
O-Subject: [RHEL 5.2 Patch 1/1] Fixes multi-threaded application hang when using huge pages on QS22
Bugzilla: 434155

RHBZ#:
------
https://bugzilla.redhat.com/show_bug.cgi?id=434155

Description:
------------
The SPU_CONTEXT_SWITCH_ACTIVE flag was only being used on two
sanity checks, which were based on the assumption that
__spu_trap_data_seg and __spu_trap_data_map are not called
during the whole save/restore process. That's not true, and
false errors were being reported when running some applications.

RHEL Version Found:
------------------
RHEL 5.1

kABI Status:
------------
No symbols were harmed.

Upstream Status:
----------------
Patch submitted upstream at:
http://patchwork.ozlabs.org/cbe-oss-dev/patch?id=16913

Test Status:
------------
Tested, confirmed.  2/29/08 <bpeters@redhat.com>

---------------------------------------------------------------

Brad Peters 1-978-392-1000 x 23183
IBM on-site partner.

Proposed Patch:
---------------
This patch is based on 2.6.18-83.el5

Acked-by: David Howells <dhowells@redhat.com>

diff --git a/arch/powerpc/platforms/cell/spu_base.c b/arch/powerpc/platforms/cell/spu_base.c
index 1ae67da..9c64e3d 100644
--- a/arch/powerpc/platforms/cell/spu_base.c
+++ b/arch/powerpc/platforms/cell/spu_base.c
@@ -154,13 +154,6 @@ static int __spu_trap_data_seg(struct spu *spu, unsigned long ea)
 
 	pr_debug("%s\n", __FUNCTION__);
 
-	if (test_bit(SPU_CONTEXT_SWITCH_ACTIVE, &spu->flags)) {
-		/* SLBs are pre-loaded for context switch, so
-		 * we should never get here!
-		 */
-		printk("%s: invalid access during switch!\n", __func__);
-		return 1;
-	}
 	esid = (ea & ESID_MASK) | SLB_ESID_V;
 
 	switch(REGION_ID(ea)) {
@@ -222,11 +215,6 @@ static int __spu_trap_data_map(struct spu *spu, unsigned long ea, u64 dsisr)
 		return 0;
 	}
 
-	if (test_bit(SPU_CONTEXT_SWITCH_ACTIVE, &spu->flags)) {
-		printk("%s: invalid access during switch!\n", __func__);
-		return 1;
-	}
-
 	spu->dar = ea;
 	spu->dsisr = dsisr;
 	mb();
diff --git a/arch/powerpc/platforms/cell/spufs/switch.c b/arch/powerpc/platforms/cell/spufs/switch.c
index 39ef503..233df8e 100644
--- a/arch/powerpc/platforms/cell/spufs/switch.c
+++ b/arch/powerpc/platforms/cell/spufs/switch.c
@@ -748,8 +748,9 @@ static inline void set_switch_active(struct spu_state *csa, struct spu *spu)
 	 * Restore, Step 23.
 	 *     Change the software context switch pending flag
 	 *     to context switch active.
+	 *
+	 *     This implementation does not uses a switch active flag.
 	 */
-	set_bit(SPU_CONTEXT_SWITCH_ACTIVE, &spu->flags);
 	clear_bit(SPU_CONTEXT_SWITCH_PENDING, &spu->flags);
 	mb();
 }
@@ -1767,9 +1768,8 @@ static inline void reset_switch_active(struct spu_state *csa, struct spu *spu)
 {
 	/* Restore, Step 74:
 	 *     Reset the "context switch active" flag.
+	 *     Not performed by this implementation.
 	 */
-	clear_bit(SPU_CONTEXT_SWITCH_ACTIVE, &spu->flags);
-	mb();
 }
 
 static inline void reenable_interrupts(struct spu_state *csa, struct spu *spu)
diff --git a/include/asm-powerpc/spu.h b/include/asm-powerpc/spu.h
index e05643a..ea1e75d 100644
--- a/include/asm-powerpc/spu.h
+++ b/include/asm-powerpc/spu.h
@@ -98,9 +98,8 @@
 #define MFC_PRIV_ATTN_EVENT                 0x00000800
 #define MFC_MULTI_SRC_EVENT                 0x00001000
 
-/* Flags indicating progress during context switch. */
+/* Flag indicating progress during context switch. */
 #define SPU_CONTEXT_SWITCH_PENDING	0UL
-#define SPU_CONTEXT_SWITCH_ACTIVE	1UL
 
 struct spu_context;
 struct spu_runqueue;