[PATCH 2/3] mm, notifier: Catch sleeping/blocking for !blockable

Daniel Vetter
2018-11-22T16:51:28Z

We need to make sure implementations don't cheat and don't have a
possible schedule/blocking point deeply burried where review can't
catch it.

I'm not sure whether this is the best way to make sure all the
might_sleep() callsites trigger, and it's a bit ugly in the code flow.
But it gets the job done.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: linux-mm@kvack.org
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
mm/mmu_notifier.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index 59e102589a25..4d282cfb296e 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -185,7 +185,13 @@ int __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
id = srcu_read_lock(&srcu);
hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
if (mn->ops->invalidate_range_start) {
- int _ret = mn->ops->invalidate_range_start(mn, mm, start, end, blockable);
+ int _ret;
+
+ if (IS_ENABLED(CONFIG_DEBUG_ATOMIC_SLEEP) && !blockable)
+ preempt_disable();
+ _ret = mn->ops->invalidate_range_start(mn, mm, start, end, blockable);
+ if (IS_ENABLED(CONFIG_DEBUG_ATOMIC_SLEEP) && !blockable)
+ preempt_enable();
if (_ret) {
pr_info("%pS callback failed with %d in %sblockable context.\n",
mn->ops->invalidate_range_start, _ret,
--
2.19.1