Messages in this thread | | | Subject | Re: [PATCH 2/3] mm, notifier: Catch sleeping/blocking for !blockable | From | Christian König <> | Date | Fri, 23 Nov 2018 11:14:44 +0100 |
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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@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.
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,
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