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, 3 insertions, 4 deletions

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index ffc7be104fc2..20e3f8702d1e 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -229,15 +229,14 @@ void vmalloc_sync_all(void)
         for (address = VMALLOC_START & PMD_MASK;
              address >= TASK_SIZE && address < FIXADDR_TOP;
              address += PMD_SIZE) {
-
-                unsigned long flags;
                 struct page *page;
 
-                spin_lock_irqsave(&pgd_lock, flags);
+                spin_lock(&pgd_lock);
                 list_for_each_entry(page, &pgd_list, lru) {
                         spinlock_t *pgt_lock;
                         pmd_t *ret;
 
+                        /* the pgt_lock only for Xen */
                         pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
 
                         spin_lock(pgt_lock);
@@ -247,7 +246,7 @@ void vmalloc_sync_all(void)
                         if (!ret)
                                 break;
                 }
-                spin_unlock_irqrestore(&pgd_lock, flags);
+                spin_unlock(&pgd_lock);
         }
 }