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, 8 insertions, 10 deletions

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index d343b3c81f3..90825f2eb0f 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -57,12 +57,10 @@ static unsigned long direct_pages_count[PG_LEVEL_NUM];
 
 void update_page_count(int level, unsigned long pages)
 {
-        unsigned long flags;
-
         /* Protect against CPA */
-        spin_lock_irqsave(&pgd_lock, flags);
+        spin_lock(&pgd_lock);
         direct_pages_count[level] += pages;
-        spin_unlock_irqrestore(&pgd_lock, flags);
+        spin_unlock(&pgd_lock);
 }
 
 static void split_page_count(int level)
@@ -394,7 +392,7 @@ static int
 try_preserve_large_page(pte_t *kpte, unsigned long address,
                         struct cpa_data *cpa)
 {
-        unsigned long nextpage_addr, numpages, pmask, psize, flags, addr, pfn;
+        unsigned long nextpage_addr, numpages, pmask, psize, addr, pfn;
         pte_t new_pte, old_pte, *tmp;
         pgprot_t old_prot, new_prot, req_prot;
         int i, do_split = 1;
@@ -403,7 +401,7 @@ try_preserve_large_page(pte_t *kpte, unsigned long address,
         if (cpa->force_split)
                 return 1;
 
-        spin_lock_irqsave(&pgd_lock, flags);
+        spin_lock(&pgd_lock);
         /*
          * Check for races, another CPU might have split this page
          * up already:
@@ -498,14 +496,14 @@ try_preserve_large_page(pte_t *kpte, unsigned long address,
         }
 
 out_unlock:
-        spin_unlock_irqrestore(&pgd_lock, flags);
+        spin_unlock(&pgd_lock);
 
         return do_split;
 }
 
 static int split_large_page(pte_t *kpte, unsigned long address)
 {
-        unsigned long flags, pfn, pfninc = 1;
+        unsigned long pfn, pfninc = 1;
         unsigned int i, level;
         pte_t *pbase, *tmp;
         pgprot_t ref_prot;
@@ -519,7 +517,7 @@ static int split_large_page(pte_t *kpte, unsigned long address)
         if (!base)
                 return -ENOMEM;
 
-        spin_lock_irqsave(&pgd_lock, flags);
+        spin_lock(&pgd_lock);
         /*
          * Check for races, another CPU might have split this page
          * up for us already:
@@ -591,7 +589,7 @@ out_unlock:
          */
         if (base)
                 __free_page(base);
-        spin_unlock_irqrestore(&pgd_lock, flags);
+        spin_unlock(&pgd_lock);
 
         return 0;
 }