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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2017-08-17 09:15:16 +0300
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2017-09-06 10:24:42 +0300
commit60f07c8ec5fae06c23e9fd7bab67dabce92b3414 (patch)
tree3c189bb7d158caba68c36b467603f94b243eea8f /arch/s390/include/asm/mmu_context.h
parentb3e5dc45fd1ec2aa1de6b80008f9295eb17e0659 (diff)
downloadlinux-60f07c8ec5fae06c23e9fd7bab67dabce92b3414.tar.xz
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/s390/include/asm/mmu_context.h')
-rw-r--r--arch/s390/include/asm/mmu_context.h4
1 files changed, 2 insertions, 2 deletions
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);