Changeset 9aed144 in mainline for kernel/arch/sparc64/src/mm/sun4u/tlb.c

Timestamp:

2011-11-25T23:35:22Z (12 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/sparc64/src/mm/sun4u/tlb.c (modified) (9 diffs)

kernel/arch/sparc64/src/mm/sun4u/tlb.c

@@ -206 +206 @@
         pte_t *t;
 
-        page_table_lock(AS, true);
         t = page_mapping_find(AS, page_16k, true);
         if (t && PTE_EXECUTABLE(t)) {
@@ -218 +217 @@
                 itsb_pte_copy(t, index);
 #endif
-                page_table_unlock(AS, true);
         } else {
                 /*
@@ -224 +222 @@
                  * handler.
                  */
-                page_table_unlock(AS, true);
                 if (as_page_fault(page_16k, PF_ACCESS_EXEC, istate) ==
                     AS_PF_FAULT) {
@@ -274 +271 @@
         }
 
-        page_table_lock(AS, true);
         t = page_mapping_find(AS, page_16k, true);
         if (t) {
@@ -286 +282 @@
                 dtsb_pte_copy(t, index, true);
 #endif
-                page_table_unlock(AS, true);
         } else {
                 /*
@@ -292 +287 @@
                  * handler.
                  */             
-                page_table_unlock(AS, true);
                 if (as_page_fault(page_16k, PF_ACCESS_READ, istate) ==
                     AS_PF_FAULT) {
@@ -318 +312 @@
         index = tag.vpn % MMU_PAGES_PER_PAGE;   /* 16K-page emulation */
 
-        page_table_lock(AS, true);
         t = page_mapping_find(AS, page_16k, true);
         if (t && PTE_WRITABLE(t)) {
@@ -334 +327 @@
                 dtsb_pte_copy(t, index, false);
 #endif
-                page_table_unlock(AS, true);
         } else {
                 /*
@@ -340 +332 @@
                  * handler.
                  */             
-                page_table_unlock(AS, true);
                 if (as_page_fault(page_16k, PF_ACCESS_WRITE, istate) ==
                     AS_PF_FAULT) {