From: Bernd Schmidt <bernds_cb1@t-online.de>
Date: Mon, 25 Aug 2008 10:41:15 +0000 (+0800)
Subject: Blackfin arch: fix bug - MPU crashes under stress
X-Git-Tag: v2.6.27-rc5~2^2~4
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3d9b7a5ce534f3963afcf8f4777267e5899fe007;p=linux-2.6

Blackfin arch: fix bug - MPU crashes under stress

Bug Description:
a customer reported under IRQ stress, running applications may
wrongly trigger an ICPLB miss and be killed. after playing a
bit more, here's a test case that may be triggering the same bug.

Fixing:
After modifying page protections, only modify the active CPLBs if the
protection change was made for the active mm.

Signed-off-by: Bernd Schmidt <bernds_cb1@t-online.de>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
---

diff --git a/include/asm-blackfin/mmu_context.h b/include/asm-blackfin/mmu_context.h
index f55ec3c23a..8529552a98 100644
--- a/include/asm-blackfin/mmu_context.h
+++ b/include/asm-blackfin/mmu_context.h
@@ -173,8 +173,10 @@ static inline void protect_page(struct mm_struct *mm, unsigned long addr,
 
 static inline void update_protections(struct mm_struct *mm)
 {
-	flush_switched_cplbs();
-	set_mask_dcplbs(mm->context.page_rwx_mask);
+	if (mm->context.page_rwx_mask == current_rwx_mask) {
+		flush_switched_cplbs();
+		set_mask_dcplbs(mm->context.page_rwx_mask);
+	}
 }
 #endif