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-rw-r--r--mm/mmu_gather.c24
1 files changed, 19 insertions, 5 deletions
diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c
index 99740e1dd273..8c943a6e1696 100644
--- a/mm/mmu_gather.c
+++ b/mm/mmu_gather.c
@@ -245,14 +245,28 @@ void tlb_finish_mmu(struct mmu_gather *tlb,
{
/*
* If there are parallel threads are doing PTE changes on same range
- * under non-exclusive lock(e.g., mmap_sem read-side) but defer TLB
- * flush by batching, a thread has stable TLB entry can fail to flush
- * the TLB by observing pte_none|!pte_dirty, for example so flush TLB
- * forcefully if we detect parallel PTE batching threads.
+ * under non-exclusive lock (e.g., mmap_sem read-side) but defer TLB
+ * flush by batching, one thread may end up seeing inconsistent PTEs
+ * and result in having stale TLB entries. So flush TLB forcefully
+ * if we detect parallel PTE batching threads.
+ *
+ * However, some syscalls, e.g. munmap(), may free page tables, this
+ * needs force flush everything in the given range. Otherwise this
+ * may result in having stale TLB entries for some architectures,
+ * e.g. aarch64, that could specify flush what level TLB.
*/
if (mm_tlb_flush_nested(tlb->mm)) {
+ /*
+ * The aarch64 yields better performance with fullmm by
+ * avoiding multiple CPUs spamming TLBI messages at the
+ * same time.
+ *
+ * On x86 non-fullmm doesn't yield significant difference
+ * against fullmm.
+ */
+ tlb->fullmm = 1;
__tlb_reset_range(tlb);
- __tlb_adjust_range(tlb, start, end - start);
+ tlb->freed_tables = 1;
}
tlb_flush_mmu(tlb);