x86/mm: Fix pgd_lock deadlock

It's forbidden to take the page_table_lock with the irq disabled
or if there's contention the IPIs (for tlb flushes) sent with
the page_table_lock held will never run leading to a deadlock.

Nobody takes the pgd_lock from irq context so the _irqsave can be
removed.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: <stable@kernel.org>
LKML-Reference: <201102162345.p1GNjMjm021738@imap1.linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 6 deletions

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 5e92b61ad574..f6089421147a 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -986,10 +986,9 @@ static void xen_pgd_pin(struct mm_struct *mm)
  */
 void xen_mm_pin_all(void)
 {
-        unsigned long flags;
         struct page *page;
 
-        spin_lock_irqsave(&pgd_lock, flags);
+        spin_lock(&pgd_lock);
 
         list_for_each_entry(page, &pgd_list, lru) {
                 if (!PagePinned(page)) {
@@ -998,7 +997,7 @@ void xen_mm_pin_all(void)
                 }
         }
 
-        spin_unlock_irqrestore(&pgd_lock, flags);
+        spin_unlock(&pgd_lock);
 }
 
 /*
@@ -1099,10 +1098,9 @@ static void xen_pgd_unpin(struct mm_struct *mm)
  */
 void xen_mm_unpin_all(void)
 {
-        unsigned long flags;
         struct page *page;
 
-        spin_lock_irqsave(&pgd_lock, flags);
+        spin_lock(&pgd_lock);
 
         list_for_each_entry(page, &pgd_list, lru) {
                 if (PageSavePinned(page)) {
@@ -1112,7 +1110,7 @@ void xen_mm_unpin_all(void)
                 }
         }
 
-        spin_unlock_irqrestore(&pgd_lock, flags);
+        spin_unlock(&pgd_lock);
 }
 
 void xen_activate_mm(struct mm_struct *prev, struct mm_struct *next)