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Howlett" , Matthew Wilcox , "Paul E . McKenney" , Jann Horn , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song , Richard Henderson , Matt Turner , Thomas Bogendoerfer , "James E . J . 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U2FsdGVkX1/aoRmCmgjbIOJ+l99my9RQuazN0MiZNP7Pnqp8Jjj861OjQIefZtCownNGC2zkJAAiQhRMyLBlwlyiDHeChA6WMGoTliRRSgoDXnCBnE9HdOP+vJct/qbixweS+j5nJ0UAtOvMzHDr/0J8UBvMOlE/VQWqNqFPGNrS3NRFR4ZBqBx5ppg0KCL2TfF++MGjgmaILwZ+ZHbCIOBn4Xbz5bQlE00uUG+V35J2DxGyj6QhWSq89hUr2KuFPmbo7pG2bNp72H0IrdBPRGG7B00WH5o7sZmsJzBRMO9CdQFCKFRqui6g3QmjO1YktKkqGUEsX6G5npRIhLJOOyU6ssgD99h73GpvGbV+9INMNJMIG9xFwgZyT4iP0HtN5g1rv2VI4+KDyjpRFlWvOXeWAnhp0uttIvpa+UF6nm9l/A78EX7pjq3MKUxHr8nfT8TV4Ysvul058i+X7uZaeViJ5A7A45Z2r86iIQL3WB91BQCRk8AJ22iXOC8UbTE3eGJXOArwBwsAgf+01KkOqUpnX8oHM7tLU85EcVPNx3SVU84NoTCnN1OXbrAQ8ac7ShLJpJ6+sZAC87D4jHii5WmvnQwJHDHW0KWrgDr5tlfjtA4dddlucv+jafO6FxZMfqlg1MrLFmXIui22Kw+PybhvfuahyLlgzOy+NWHdEkxFvrcqXfrujtlZtwbwLxVv+4ROAKBWzyzhfpR2RCgJgWUSmVap8Gnx9Dy9o3ZXLgmTR+KV0PhLK63d2WhFa12JhZBVr02UnMfaDYBkYzXaRTONOuk9MG5q5m/GKeCvnmfxnhYsridcBOgM/U2zvjbUeXy8zH6v9RzcU8Ie59RVm0chIYc/RRTN16ZtJpI65Q/UeAr1nf9WgAIHjWsRLNDVcrTNZ2gVic9RHSG0GIdjDe3DngfLX9yIS4Rl06MzorzWMrHaDke0SFEvpnwuuxtkAoqRyyIJZbWRCnRQsXt qW+20QcP 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Oct 25, 2024 at 11:56:52PM +0200, Vlastimil Babka wrote: > On 10/25/24 19:12, Lorenzo Stoakes wrote: > > On Wed, Oct 23, 2024 at 05:24:40PM +0100, Lorenzo Stoakes wrote: > >> Implement a new lightweight guard page feature, that is regions of userland > >> virtual memory that, when accessed, cause a fatal signal to arise. > > > > > > > > Hi Andrew - Could you apply the below fix-patch? I realise we must handle > > fatal signals and conditional rescheduling in the vector_madvise() special > > case. > > > > Thanks! > > > > ----8<---- > > From 546d7e1831c71599fc733d589e0d75f52e84826d Mon Sep 17 00:00:00 2001 > > From: Lorenzo Stoakes > > Date: Fri, 25 Oct 2024 18:05:48 +0100 > > Subject: [PATCH] mm: yield on fatal signal/cond_sched() in vector_madvise() > > > > While we have to treat -ERESTARTNOINTR specially here as we are looping > > through a vector of operations and can't simply restart the entire > > operation, we mustn't hold up fatal signals or RT kernels. > > For plain madvise() syscall returning -ERESTARTNOINTR does the right thing > and checks fatal_signal_pending() before returning, right? I believe so. But now you've caused me some doubt so let me double check and make absolutely sure :) > > Uh actually can we be just returning -ERESTARTNOINTR or do we need to use > restart_syscall()? Yeah I was wondering about that, but restart_syscall() seems to set TIF_SIGPENDING, and I wondered if that was correct... but then I saw other places that seemed to use it direct so it seemed so. Let's eliminiate doubt, will check this next week and make sure. > > > --- > > mm/madvise.c | 8 +++++++- > > 1 file changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/mm/madvise.c b/mm/madvise.c > > index 48eba25e25fe..127aa5d86656 100644 > > --- a/mm/madvise.c > > +++ b/mm/madvise.c > > @@ -1713,8 +1713,14 @@ static ssize_t vector_madvise(struct mm_struct *mm, struct iov_iter *iter, > > * we have already rescinded locks, it should be no problem to > > * simply try again. > > */ > > - if (ret == -ERESTARTNOINTR) > > + if (ret == -ERESTARTNOINTR) { > > + if (fatal_signal_pending(current)) { > > + ret = -EINTR; > > + break; > > + } > > + cond_resched(); > > Should be unnecessary as we're calling an operation that takes a rwsem so > there are reschedule points already. And with lazy preempt hopefully > cond_resched()s will become history, so let's not add more only to delete later. Ack will remove on respin. > > > continue; > > + } > > if (ret < 0) > > break; > > iov_iter_advance(iter, iter_iov_len(iter)); > > -- > > 2.47.0 > For simplicitly with your other comments too I think I'll respin this next week.