X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=blobdiff_plain;f=mm%2Fmmu_gather.c;h=8c943a6e1696c095d77ae65bb5d784cc09a85afd;hb=c884d8ac7ffccc094e9674a3eb3be90d3b296c0a;hp=99740e1dd27304b31097eb3deedc309a6c398490;hpb=c32beba325d8c54d8affa158a0a54643ba87eab4;p=linux.git

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);