Changeset 9aed144 in mainline for kernel/arch/ia64/src/mm/tlb.c

Timestamp:

2011-11-25T23:35:22Z (13 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

1c01e6c

Parents:

50177dcd

Message:

Finish transition to lock-free page_mapping_find() in TLB miss handlers.

• Simply drop the calls to page_table_lock/unlock() in ia64 and sparc64 TLB miss handlers.

As for why this is possible:

• page_mapping_find() cannot race with page_table_remove() because page_mapping_find() is called only when interrupts are disabled, which prevents TLB shootdown from starting, which in turn prevents page_table_remove() from running

• page_mapping_insert() will not negatively interfere with page_mapping_find() because page_mapping_insert() adds a fully initialized pte_t to the end of the hash bucket

File:

• kernel/arch/ia64/src/mm/tlb.c (modified) (14 diffs)

kernel/arch/ia64/src/mm/tlb.c

@@ -480 +480 @@
         va = istate->cr_ifa; /* faulting address */
         
-        page_table_lock(AS, true);
         t = page_mapping_find(AS, va, true);
         if (t) {
@@ -488 +487 @@
                  */
                 itc_pte_copy(t);
-                page_table_unlock(AS, true);
         } else {
                 /*
                  * Forward the page fault to address space page fault handler.
                  */
-                page_table_unlock(AS, true);
                 if (as_page_fault(va, PF_ACCESS_EXEC, istate) == AS_PF_FAULT) {
                         fault_if_from_uspace(istate, "Page fault at %p.",
@@ -598 +595 @@
         
         
-        page_table_lock(AS, true);
         pte_t *entry = page_mapping_find(AS, va, true);
         if (entry) {
@@ -606 +602 @@
                  */
                 dtc_pte_copy(entry);
-                page_table_unlock(AS, true);
         } else {
-                page_table_unlock(AS, true);
                 if (try_memmap_io_insertion(va, istate))
                         return;
@@ -650 +644 @@
         va = istate->cr_ifa;  /* faulting address */
         
-        page_table_lock(AS, true);
         t = page_mapping_find(AS, va, true);
         ASSERT((t) && (t->p));
@@ -667 +660 @@
                 }
         }
-        page_table_unlock(AS, true);
 }
 
@@ -683 +675 @@
         va = istate->cr_ifa;  /* faulting address */
         
-        page_table_lock(AS, true);
         t = page_mapping_find(AS, va, true);
         ASSERT((t) && (t->p));
@@ -700 +691 @@
                 }
         }
-        page_table_unlock(AS, true);
 }
 
@@ -716 +706 @@
         va = istate->cr_ifa;  /* faulting address */
         
-        page_table_lock(AS, true);
         t = page_mapping_find(AS, va, true);
         ASSERT((t) && (t->p));
@@ -733 +722 @@
                 }
         }
-        page_table_unlock(AS, true);
 }
 
@@ -752 +740 @@
          * Assume a write to a read-only page.
          */
-        page_table_lock(AS, true);
         t = page_mapping_find(AS, va, true);
         ASSERT((t) && (t->p));
@@ -761 +748 @@
                 panic_memtrap(istate, PF_ACCESS_WRITE, va, NULL);
         }
-        page_table_unlock(AS, true);
 }
 
@@ -777 +763 @@
         va = istate->cr_ifa;  /* faulting address */
         
-        page_table_lock(AS, true);
         t = page_mapping_find(AS, va, true);
         ASSERT(t);
@@ -790 +775 @@
                 else
                         dtc_pte_copy(t);
-                page_table_unlock(AS, true);
         } else {
-                page_table_unlock(AS, true);
                 if (as_page_fault(va, PF_ACCESS_READ, istate) == AS_PF_FAULT) {
                         fault_if_from_uspace(istate, "Page fault at %p.",