spinlock: lockbreak cleanup

The break_lock data structure and code for spinlocks is quite nasty.
Not only does it double the size of a spinlock but it changes locking to
a potentially less optimal trylock.

Put all of that under CONFIG_GENERIC_LOCKBREAK, and introduce a
__raw_spin_is_contended that uses the lock data itself to determine whether
there are waiters on the lock, to be used if CONFIG_GENERIC_LOCKBREAK is
not set.

Rename need_lockbreak to spin_needbreak, make it use spin_is_contended to
decouple it from the spinlock implementation, and make it typesafe (rwlocks
do not have any need_lockbreak sites -- why do they even get bloated up
with that break_lock then?).

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 3 insertions, 5 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 4b0144b24c12..673ebbf499c7 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -513,8 +513,7 @@ again:
                 if (progress >= 32) {
                         progress = 0;
                         if (need_resched() ||
-                            need_lockbreak(src_ptl) ||
-                            need_lockbreak(dst_ptl))
+                            spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
                                 break;
                 }
                 if (pte_none(*src_pte)) {
@@ -853,7 +852,7 @@ unsigned long unmap_vmas(struct mmu_gather **tlbp,
                         tlb_finish_mmu(*tlbp, tlb_start, start);
 
                         if (need_resched() ||
-                                (i_mmap_lock && need_lockbreak(i_mmap_lock))) {
+                                (i_mmap_lock && spin_needbreak(i_mmap_lock))) {
                                 if (i_mmap_lock) {
                                         *tlbp = NULL;
                                         goto out;
@@ -1768,8 +1767,7 @@ again:
 
         restart_addr = zap_page_range(vma, start_addr,
                                         end_addr - start_addr, details);
-        need_break = need_resched() ||
-                        need_lockbreak(details->i_mmap_lock);
+        need_break = need_resched() || spin_needbreak(details->i_mmap_lock);
 
         if (restart_addr >= end_addr) {
                 /* We have now completed this vma: mark it so */