Re: [PATCH 2/3] mm, notifier: Catch sleeping/blocking for !blockable
From: Christian KÃnig
Date: Fri Nov 23 2018 - 05:14:49 EST
Am 23.11.18 um 09:46 schrieb Daniel Vetter:
On Thu, Nov 22, 2018 at 06:55:17PM +0000, Koenig, Christian wrote:
Am 22.11.18 um 17:51 schrieb Daniel Vetter:
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@xxxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: "Christian KÃnig" <christian.koenig@xxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: "JÃrÃme Glisse" <jglisse@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
---
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();
Just for the sake of better documenting this how about adding this to
include/linux/kernel.h right next to might_sleep():
#define disallow_sleeping_if(cond)ÂÂÂ for((cond) ? preempt_disable() :
(void)0; (cond); preempt_disable())
(Just from the back of my head, might contain peanuts and/or hints of
errors).
I think these magic for blocks aren't used in the kernel. goto breaks
them, and we use goto a lot.
Yeah, good argument.
I think a disallow/allow_sleep() pair with
the conditional preept_disable/enable() calls would be nice though. I can
do that if the overall idea sticks.
Sounds like a good idea to me as well.
Christian.
-Daniel
Christian.
if (_ret) {
pr_info("%pS callback failed with %d in %sblockable context.\n",
mn->ops->invalidate_range_start, _ret,