When building the kernel with sparse enabled 'C=1' the following
warnings can be seen:
fs/proc/task_mmu.c:587:17: warning: context imbalance in 'smaps_pte_range' - unexpected unlock
fs/proc/task_mmu.c:1145:28: warning: context imbalance in 'clear_refs_pte_range' - unexpected unlock
fs/proc/task_mmu.c:1473:28: warning: context imbalance in 'pagemap_pmd_range' - unexpected unlock
fs/proc/task_mmu.c:1811:28: warning: context imbalance in 'gather_pte_stats' - unexpected unlock
Rework to add __acquire() and __release() to tell sparse that it is all good.
Signed-off-by: Anders Roxell <[email protected]>
---
fs/proc/task_mmu.c | 31 +++++++++++++++++++++++++++++++
mm/huge_memory.c | 4 +++-
2 files changed, 34 insertions(+), 1 deletion(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index ad667dbc96f5..6b702c030802 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -584,6 +584,13 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
ptl = pmd_trans_huge_lock(pmd, vma);
if (ptl) {
+ /*
+ * Fake out sparse.
+ * The pmd_lock are held in pmd_trans_huge_lock() and if we
+ * get in here we have to unlock. We tell sparse that
+ * everyting is as it should with the __acquire() directive.
+ */
+ __acquire(ptl);
smaps_pmd_entry(pmd, addr, walk);
spin_unlock(ptl);
goto out;
@@ -1127,6 +1134,14 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
ptl = pmd_trans_huge_lock(pmd, vma);
if (ptl) {
+ /*
+ * Fake out sparse.
+ * The pmd_lock are held in pmd_trans_huge_lock() and if we
+ * get in here we have to unlock. We tell sparse that
+ * everyting is as it should with the __acquire() directive.
+ */
+ __acquire(ptl);
+
if (cp->type == CLEAR_REFS_SOFT_DIRTY) {
clear_soft_dirty_pmd(vma, addr, pmd);
goto out;
@@ -1418,6 +1433,14 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end,
pmd_t pmd = *pmdp;
struct page *page = NULL;
+ /*
+ * Fake out sparse.
+ * The pmd_lock are held in pmd_trans_huge_lock() and if we
+ * get in here we have to unlock. We tell sparse that
+ * everyting is as it should with the __acquire() directive.
+ */
+ __acquire(ptl);
+
if (vma->vm_flags & VM_SOFTDIRTY)
flags |= PM_SOFT_DIRTY;
@@ -1804,6 +1827,14 @@ static int gather_pte_stats(pmd_t *pmd, unsigned long addr,
if (ptl) {
struct page *page;
+ /*
+ * Fake out sparse.
+ * The pmd_lock are held in pmd_trans_huge_lock() and if we
+ * get in here we have to unlock. We tell sparse that
+ * everyting is as it should with the __acquire() directive.
+ */
+ __acquire(ptl);
+
page = can_gather_numa_stats_pmd(*pmd, vma, addr);
if (page)
gather_stats(page, md, pmd_dirty(*pmd),
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e5ea5f775d5c..c873bf5947ae 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1833,8 +1833,10 @@ spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
spinlock_t *ptl;
ptl = pmd_lock(vma->vm_mm, pmd);
if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
- pmd_devmap(*pmd)))
+ pmd_devmap(*pmd))) {
+ __release(ptl); /* fake out sparse */
return ptl;
+ }
spin_unlock(ptl);
return NULL;
}
--
2.33.0
On Thu, Oct 07, 2021 at 09:16:36PM +0200, Anders Roxell wrote:
> When building the kernel with sparse enabled 'C=1' the following
> warnings can be seen:
>
> fs/proc/task_mmu.c:587:17: warning: context imbalance in 'smaps_pte_range' - unexpected unlock
> fs/proc/task_mmu.c:1145:28: warning: context imbalance in 'clear_refs_pte_range' - unexpected unlock
> fs/proc/task_mmu.c:1473:28: warning: context imbalance in 'pagemap_pmd_range' - unexpected unlock
> fs/proc/task_mmu.c:1811:28: warning: context imbalance in 'gather_pte_stats' - unexpected unlock
>
> Rework to add __acquire() and __release() to tell sparse that it is all good.
Surely the root problem here is that pmd_trans_huge_lock() isn't
marked with __cond_lock() like, eg, get_locked_pte() is?