[PATCH v4 05/11] powerpc/perf: Applies counting method to monitor lockless pgtbl walks

Leonardo Bras
2019-09-27T23:40:02Z

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

Signed-off-by: Leonardo Bras <leonardo@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