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Mon, 11 Mar 2024 20:07:03 +0800 Date: Mon, 11 Mar 2024 20:06:59 +0800 From: Changbin Du To: Mark Rutland CC: Changbin Du , Ingo Molnar , Andrew Morton , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , , , Alexander Potapenko , , Marco Elver Subject: Re: [PATCH] mm: kmsan: fix instrumentation recursion on preempt_count Message-ID: <20240311120659.2la4s5vwms5jebut@M910t> References: <20240311112330.372158-1-changbin.du@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-Originating-IP: [10.110.54.157] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To kwepemd100011.china.huawei.com (7.221.188.204) X-Rspamd-Queue-Id: D30EA2001B X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: iiea3k6wgupy7ttz5ikyewpc7gh4ea41 X-HE-Tag: 1710158830-167880 X-HE-Meta: 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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 Mon, Mar 11, 2024 at 11:42:29AM +0000, Mark Rutland wrote: > On Mon, Mar 11, 2024 at 07:23:30PM +0800, Changbin Du wrote: > > This disables msan check for preempt_count_{add,sub} to fix a > > instrumentation recursion issue on preempt_count: > > > > __msan_metadata_ptr_for_load_4() -> kmsan_virt_addr_valid() -> > > preempt_disable() -> __msan_metadata_ptr_for_load_4() > > > > With this fix, I was able to run kmsan kernel with: > > o CONFIG_DEBUG_KMEMLEAK=n > > o CONFIG_KFENCE=n > > o CONFIG_LOCKDEP=n > > > > KMEMLEAK and KFENCE generate too many false positives in unwinding code. > > LOCKDEP still introduces instrumenting recursions issue. But these are > > other issues expected to be fixed. > > > > Cc: Marco Elver > > Signed-off-by: Changbin Du > > --- > > kernel/sched/core.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > index 9116bcc90346..5b63bb98e60a 100644 > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -5848,7 +5848,7 @@ static inline void preempt_latency_start(int val) > > } > > } > > > > -void preempt_count_add(int val) > > +void __no_kmsan_checks preempt_count_add(int val) > > { > > #ifdef CONFIG_DEBUG_PREEMPT > > /* > > @@ -5880,7 +5880,7 @@ static inline void preempt_latency_stop(int val) > > trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip()); > > } > > What prevents a larger loop via one of the calles of preempt_count_{add,sub}() > > For example, via preempt_latency_{start,stop}() ? > > ... or via some *other* instrumentation that might be placed in those? > > I suspect we should be using noinstr or __always_inline in a bunch of places to > clean this up properly. > In my local build, these two are not that small for inlining. (I has preempt_off tracer enabled). $ readelf -s vmlinux | grep -sw -E 'preempt_count_add|preempt_count_sub' 157043: ffffffff81174de0 186 FUNC GLOBAL DEFAULT 1 preempt_count_add 157045: ffffffff81174eb0 216 FUNC GLOBAL DEFAULT 1 preempt_count_sub The noinstr adds __no_sanitize_memory to the tagged functions so we might see many false positives. > Mark. -- Cheers, Changbin Du