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>

5 files changed, 22 insertions, 30 deletions

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index ffc7be104fc..20e3f8702d1 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);
         }
 }
 
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 71a59296af8..c14a5422e15 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -105,18 +105,18 @@ void sync_global_pgds(unsigned long start, unsigned long end)
 
         for (address = start; address <= end; address += PGDIR_SIZE) {
                 const pgd_t *pgd_ref = pgd_offset_k(address);
-                unsigned long flags;
                 struct page *page;
 
                 if (pgd_none(*pgd_ref))
                         continue;
 
-                spin_lock_irqsave(&pgd_lock, flags);
+                spin_lock(&pgd_lock);
                 list_for_each_entry(page, &pgd_list, lru) {
                         pgd_t *pgd;
                         spinlock_t *pgt_lock;
 
                         pgd = (pgd_t *)page_address(page) + pgd_index(address);
+                        /* the pgt_lock only for Xen */
                         pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
                         spin_lock(pgt_lock);
 
@@ -128,7 +128,7 @@ void sync_global_pgds(unsigned long start, unsigned long end)
 
                         spin_unlock(pgt_lock);
                 }
-                spin_unlock_irqrestore(&pgd_lock, flags);
+                spin_unlock(&pgd_lock);
         }
 }
 
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;
 }
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 500242d3c96..0113d19c8aa 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -121,14 +121,12 @@ static void pgd_ctor(struct mm_struct *mm, pgd_t *pgd)
 
 static void pgd_dtor(pgd_t *pgd)
 {
-        unsigned long flags; /* can be called from interrupt context */
-
         if (SHARED_KERNEL_PMD)
                 return;
 
-        spin_lock_irqsave(&pgd_lock, flags);
+        spin_lock(&pgd_lock);
         pgd_list_del(pgd);
-        spin_unlock_irqrestore(&pgd_lock, flags);
+        spin_unlock(&pgd_lock);
 }
 
 /*
@@ -260,7 +258,6 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
 {
         pgd_t *pgd;
         pmd_t *pmds[PREALLOCATED_PMDS];
-        unsigned long flags;
 
         pgd = (pgd_t *)__get_free_page(PGALLOC_GFP);
 
@@ -280,12 +277,12 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
          * respect to anything walking the pgd_list, so that they
          * never see a partially populated pgd.
          */
-        spin_lock_irqsave(&pgd_lock, flags);
+        spin_lock(&pgd_lock);
 
         pgd_ctor(mm, pgd);
         pgd_prepopulate_pmd(mm, pgd, pmds);
 
-        spin_unlock_irqrestore(&pgd_lock, flags);
+        spin_unlock(&pgd_lock);
 
         return pgd;
 
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 5e92b61ad57..f6089421147 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)