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Sun, 16 Jun 2024 16:05:41 +0000 (UTC) Message-ID: <139fd239-49e3-4591-965e-82c9f7d627e9@redhat.com> Date: Sun, 16 Jun 2024 12:05:40 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [mm?] possible deadlock in __mmap_lock_do_trace_start_locking To: syzbot , akpm@linux-foundation.org, cgroups@vger.kernel.org, hannes@cmpxchg.org, hawk@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, lizefan.x@bytedance.com, mathieu.desnoyers@efficios.com, mhiramat@kernel.org, netdev@vger.kernel.org, rostedt@goodmis.org, syzkaller-bugs@googlegroups.com, tj@kernel.org References: <000000000000d05580061b025528@google.com> Content-Language: en-US From: Waiman Long In-Reply-To: <000000000000d05580061b025528@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C3A4A140023 X-Stat-Signature: ffdc81ztahdxfmc6p7bttwirw4kiriwb X-Rspam-User: X-HE-Tag: 1718553954-752043 X-HE-Meta: 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 GxKCe3rF 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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 6/16/24 10:05, syzbot wrote: > syzbot has bisected this issue to: > > commit 21c38a3bd4ee3fb7337d013a638302fb5e5f9dc2 > Author: Jesper Dangaard Brouer > Date: Wed May 1 14:04:11 2024 +0000 > > cgroup/rstat: add cgroup_rstat_cpu_lock helpers and tracepoints > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=16695261980000 > start commit: 36534d3c5453 tcp: use signed arithmetic in tcp_rtx_probe0_.. > git tree: bpf > final oops: https://syzkaller.appspot.com/x/report.txt?x=15695261980000 > console output: https://syzkaller.appspot.com/x/log.txt?x=11695261980000 > kernel config: https://syzkaller.appspot.com/x/.config?x=333ebe38d43c42e2 > dashboard link: https://syzkaller.appspot.com/bug?extid=6ff90931779bcdfc840c > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1585acfa980000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17bdb7ee980000 > > Reported-by: syzbot+6ff90931779bcdfc840c@syzkaller.appspotmail.com > Fixes: 21c38a3bd4ee ("cgroup/rstat: add cgroup_rstat_cpu_lock helpers and tracepoints") > > For information about bisection process see: https://goo.gl/tpsmEJ#bisection > +static __always_inline +unsigned long _cgroup_rstat_cpu_lock(raw_spinlock_t *cpu_lock, int cpu, +                                    struct cgroup *cgrp, const bool fast_path) +{ +       unsigned long flags; +       bool contended; + +       /* +        * The _irqsave() is needed because cgroup_rstat_lock is +        * spinlock_t which is a sleeping lock on PREEMPT_RT. Acquiring +        * this lock with the _irq() suffix only disables interrupts on +        * a non-PREEMPT_RT kernel. The raw_spinlock_t below disables +        * interrupts on both configurations. The _irqsave() ensures +        * that interrupts are always disabled and later restored. +        */ +       contended = !raw_spin_trylock_irqsave(cpu_lock, flags); +       if (contended) { +               if (fast_path) + trace_cgroup_rstat_cpu_lock_contended_fastpath(cgrp, cp> +               else +                       trace_cgroup_rstat_cpu_lock_contended(cgrp, cpu, conten> + +               raw_spin_lock_irqsave(cpu_lock, flags); +       } I believe the problem may be caused by the fact that trace_cgroup_rstat_cpu_lock_contended*() can be called with IRQ enabled. I had suggested before IRQ should be disabled first before doing any trace operation. See https://lore.kernel.org/linux-mm/203fdb35-f4cf-4754-9709-3c024eecade9@redhat.com/ Doing so may be able to resolve this possible deadlock. Cheers, Longman