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>

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index ffc7be104fc2a955f33d2fb59101752ee7d1ac2d..20e3f8702d1e5701b130d2891e23bf39fbe81663 100644 (file)
--- 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 71a59296af80779f56d3f31c98f0ce2d790fe373..c14a5422e15226e72b1b7bc9655a0982ea706555 100644 (file)
--- 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 d343b3c81f3c1e79a7a4f21eb51dc4672f7a1c9b..90825f2eb0f4ef25c9f4d474b29d6a986014f012 100644 (file)
--- 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 500242d3c96d61741607af926d3675ed9a309c46..0113d19c8aa60985764dfce5bcc4488c8ee57c5c 100644 (file)
--- 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 5e92b61ad574dd6514f09644737dd450d0311dd0..f6089421147a0affdc98916081a7fbf54eb70b39 100644 (file)
--- 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)