path: root/arch/arm/include
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authorWill Deacon <will.deacon@arm.com>2013-02-28 17:47:36 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2013-03-03 22:54:14 +0000
commit8a4e3a9ead7e37ce1505602b564c15da09ac039f (patch)
tree5cc8ad188810649ea0739c769977451b825e4325 /arch/arm/include
parent37f47e3d62533c931b04cb409f2eb299e6342331 (diff)
ARM: 7659/1: mm: make mm->context.id an atomic64_t variable
mm->context.id is updated under asid_lock when a new ASID is allocated to an mm_struct. However, it is also read without the lock when a task is being scheduled and checking whether or not the current ASID generation is up-to-date. If two threads of the same process are being scheduled in parallel and the bottom bits of the generation in their mm->context.id match the current generation (that is, the mm_struct has not been used for ~2^24 rollovers) then the non-atomic, lockless access to mm->context.id may yield the incorrect ASID. This patch fixes this issue by making mm->context.id and atomic64_t, ensuring that the generation is always read consistently. For code that only requires access to the ASID bits (e.g. TLB flushing by mm), then the value is accessed directly, which GCC converts to an ldrb. Cc: <stable@vger.kernel.org> # 3.8 Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/include')
2 files changed, 5 insertions, 5 deletions
diff --git a/arch/arm/include/asm/mmu.h b/arch/arm/include/asm/mmu.h
index 9f77e7804f3..e3d55547e75 100644
--- a/arch/arm/include/asm/mmu.h
+++ b/arch/arm/include/asm/mmu.h
@@ -5,15 +5,15 @@
typedef struct {
- u64 id;
+ atomic64_t id;
- unsigned int vmalloc_seq;
+ unsigned int vmalloc_seq;
} mm_context_t;
#define ASID_BITS 8
#define ASID_MASK ((~0ULL) << ASID_BITS)
-#define ASID(mm) ((mm)->context.id & ~ASID_MASK)
+#define ASID(mm) ((mm)->context.id.counter & ~ASID_MASK)
#define ASID(mm) (0)
@@ -26,7 +26,7 @@ typedef struct {
* modified for 2.6 by Hyok S. Choi <hyok.choi@samsung.com>
typedef struct {
- unsigned long end_brk;
+ unsigned long end_brk;
} mm_context_t;
diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h
index e1f644bc7cc..863a6611323 100644
--- a/arch/arm/include/asm/mmu_context.h
+++ b/arch/arm/include/asm/mmu_context.h
@@ -25,7 +25,7 @@ void __check_vmalloc_seq(struct mm_struct *mm);
void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk);
-#define init_new_context(tsk,mm) ({ mm->context.id = 0; })
+#define init_new_context(tsk,mm) ({ atomic64_set(&mm->context.id, 0); 0; })
#else /* !CONFIG_CPU_HAS_ASID */