[PATCH v2 05/11] powerpc/perf: Applies counting method to monitor lockless pgtbl walks

[Leonardo Bras]

Applies the counting-based method for monitoring lockless pgtable walks on
read_user_stack_slow.

Signed-off-by: Leonardo Bras <leona...@linux.ibm.com>
---
 arch/powerpc/perf/callchain.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
index c84bbd4298a0..9d76194a2a8f 100644
--- a/arch/powerpc/perf/callchain.c
+++ b/arch/powerpc/perf/callchain.c
@@ -113,16 +113,18 @@ static int read_user_stack_slow(void __user *ptr, void 
*buf, int nb)
        int ret = -EFAULT;
        pgd_t *pgdir;
        pte_t *ptep, pte;
+       struct mm_struct *mm = current->mm;
        unsigned shift;
        unsigned long addr = (unsigned long) ptr;
        unsigned long offset;
        unsigned long pfn, flags;
        void *kaddr;
 
-       pgdir = current->mm->pgd;
+       pgdir = mm->pgd;
        if (!pgdir)
                return -EFAULT;
 
+       start_lockless_pgtbl_walk(mm);
        local_irq_save(flags);
        ptep = find_current_mm_pte(pgdir, addr, NULL, &shift);
        if (!ptep)
@@ -146,6 +148,7 @@ static int read_user_stack_slow(void __user *ptr, void 
*buf, int nb)
        ret = 0;
 err_out:
        local_irq_restore(flags);
+       end_lockless_pgtbl_walk(mm);
        return ret;
 }
 
-- 
2.20.1