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McKenney" , Marco Elver , linux-kernel@vger.kernel.org, tj@kernel.org, gregkh@linuxfoundation.org Subject: Re: [BUG] -next lockdep invalid wait context Message-ID: References: <41619255-cdc2-4573-a360-7794fc3614f7@paulmck-laptop> <66a745bb-d381-471c-aeee-3800a504f87d@paulmck-laptop> <20241102001224.2789-1-hdanton@sina.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241102001224.2789-1-hdanton@sina.com> On Sat, Nov 02, 2024 at 08:12:24AM +0800, Hillf Danton wrote: > On Thu, 31 Oct 2024 08:21:36 +0100 Sebastian Andrzej Siewior > > On 2024-10-30 16:10:58 [-0700], Paul E. McKenney wrote: > > > > > > So I need to avoid calling kfree() within an smp_call_function() handler? > > > > Yes. No kmalloc()/ kfree() in IRQ context. > > > Another splat [1] with no link to kmalloc()/ kfree(). > Because it's a different bug. schedule(): __schedule(): rq_lock(); // <- rq lock is a raw spin lock, so no sleep inside switch_mm_irqs_off(): trace_tlb_flush(): bpf_trace_run2(): stack_map_get_build_id_offset(): mmap_read_trylock(): // this is actually ok, because // trylock() on rwsem won't // sleep. __mmap_lock_trace_acquire_returned(): get_mm_memcg_path(): cgroup_path(): kernfs_path_from_node(): read_lock_irqsave(); // on RT, read_lock() // is a rwsem IIUC, // so might sleep. // hence the issue. Maybe kernfs can use RCU instead of read_lock here? I don't know... Regards, Boqun > [ BUG: Invalid wait context ] > 6.12.0-rc5-next-20241031-syzkaller #0 Not tainted > ----------------------------- > strace-static-x/5846 is trying to lock: > ffffffff8eac8698 (kernfs_rename_lock){....}-{3:3}, at: kernfs_path_from_node+0x92/0xb00 fs/kernfs/dir.c:229 > other info that might help us debug this: > context-{5:5} > 3 locks held by strace-static-x/5846: > #0: ffff8880b873e598 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:598 > #1: ffffffff8e939f20 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline] > #1: ffffffff8e939f20 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] > #1: ffffffff8e939f20 (rcu_read_lock){....}-{1:3}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2339 [inline] > #1: ffffffff8e939f20 (rcu_read_lock){....}-{1:3}, at: bpf_trace_run2+0x1fc/0x540 kernel/trace/bpf_trace.c:2381 > #2: ffff88802f7129e0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_trylock include/linux/mmap_lock.h:208 [inline] > #2: ffff88802f7129e0 (&mm->mmap_lock){++++}-{4:4}, at: stack_map_get_build_id_offset+0x431/0x870 kernel/bpf/stackmap.c:157 > > [1] Subject: [syzbot] [kernfs?] WARNING: locking bug in kernfs_path_from_node > https://lore.kernel.org/lkml/67251dc6.050a0220.529b6.015e.GAE@google.com/