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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2017-08-17 08:15:16 +0200
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2017-09-06 09:24:42 +0200
commit60f07c8ec5fae06c23e9fd7bab67dabce92b3414 (patch)
tree3c189bb7d158caba68c36b467603f94b243eea8f /arch
parentb3e5dc45fd1ec2aa1de6b80008f9295eb17e0659 (diff)
s390/mm: fix race on mm->context.flush_mm
The order in __tlb_flush_mm_lazy is to flush TLB first and then clear the mm->context.flush_mm bit. This can lead to missed flushes as the bit can be set anytime, the order needs to be the other way aronud. But this leads to a different race, __tlb_flush_mm_lazy may be called on two CPUs concurrently. If mm->context.flush_mm is cleared first then another CPU can bypass __tlb_flush_mm_lazy although the first CPU has not done the flush yet. In a virtualized environment the time until the flush is finally completed can be arbitrarily long. Add a spinlock to serialize __tlb_flush_mm_lazy and use the function in finish_arch_post_lock_switch as well. Cc: <stable@vger.kernel.org> Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/s390/include/asm/mmu.h2
-rw-r--r--arch/s390/include/asm/mmu_context.h4
-rw-r--r--arch/s390/include/asm/tlbflush.h4
3 files changed, 7 insertions, 3 deletions
diff --git a/arch/s390/include/asm/mmu.h b/arch/s390/include/asm/mmu.h
index bd6f30304518..3525fe6e7e4c 100644
--- a/arch/s390/include/asm/mmu.h
+++ b/arch/s390/include/asm/mmu.h
@@ -5,6 +5,7 @@
#include <linux/errno.h>
typedef struct {
+ spinlock_t lock;
cpumask_t cpu_attach_mask;
atomic_t flush_count;
unsigned int flush_mm;
@@ -27,6 +28,7 @@ typedef struct {
} mm_context_t;
#define INIT_MM_CONTEXT(name) \
+ .context.lock = __SPIN_LOCK_UNLOCKED(name.context.lock), \
.context.pgtable_lock = \
__SPIN_LOCK_UNLOCKED(name.context.pgtable_lock), \
.context.pgtable_list = LIST_HEAD_INIT(name.context.pgtable_list), \
diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
index 8823e35f69a9..484efe8f4234 100644
--- a/arch/s390/include/asm/mmu_context.h
+++ b/arch/s390/include/asm/mmu_context.h
@@ -17,6 +17,7 @@
static inline int init_new_context(struct task_struct *tsk,
struct mm_struct *mm)
{
+ spin_lock_init(&mm->context.lock);
spin_lock_init(&mm->context.pgtable_lock);
INIT_LIST_HEAD(&mm->context.pgtable_list);
spin_lock_init(&mm->context.gmap_lock);
@@ -121,8 +122,7 @@ static inline void finish_arch_post_lock_switch(void)
while (atomic_read(&mm->context.flush_count))
cpu_relax();
cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
- if (mm->context.flush_mm)
- __tlb_flush_mm(mm);
+ __tlb_flush_mm_lazy(mm);
preempt_enable();
}
set_fs(current->thread.mm_segment);
diff --git a/arch/s390/include/asm/tlbflush.h b/arch/s390/include/asm/tlbflush.h
index 16fe2a3d9a03..b08d5bc2666e 100644
--- a/arch/s390/include/asm/tlbflush.h
+++ b/arch/s390/include/asm/tlbflush.h
@@ -101,10 +101,12 @@ static inline void __tlb_flush_kernel(void)
static inline void __tlb_flush_mm_lazy(struct mm_struct * mm)
{
+ spin_lock(&mm->context.lock);
if (mm->context.flush_mm) {
- __tlb_flush_mm(mm);
mm->context.flush_mm = 0;
+ __tlb_flush_mm(mm);
}
+ spin_unlock(&mm->context.lock);
}
/*