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@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();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) 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. 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. -Daniel
Christian.
if (_ret) { pr_info("%pS callback failed with %d in %sblockable context.\n", mn->ops->invalidate_range_start, _ret,