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Date: Mon, 1 Feb 2021 12:53:53 -0500 From: Waiman Long <longman@...hat.com> To: Peter Zijlstra <peterz@...radead.org>, Dmitry Vyukov <dvyukov@...gle.com> Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, andrii@...nel.org, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, kpsingh@...nel.org, netdev <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...hat.com> Subject: Re: corrupted pvqspinlock in htab_map_update_elem On 2/1/21 6:23 AM, Peter Zijlstra wrote: > On Mon, Feb 01, 2021 at 10:50:58AM +0100, Peter Zijlstra wrote: > >>> queued_spin_unlock arch/x86/include/asm/qspinlock.h:56 [inline] >>> lockdep_unlock+0x10e/0x290 kernel/locking/lockdep.c:124 >>> debug_locks_off_graph_unlock kernel/locking/lockdep.c:165 [inline] >>> print_usage_bug kernel/locking/lockdep.c:3710 [inline] >> Ha, I think you hit a bug in lockdep. > Something like so I suppose. > > --- > Subject: locking/lockdep: Avoid unmatched unlock > From: Peter Zijlstra <peterz@...radead.org> > Date: Mon Feb 1 11:55:38 CET 2021 > > Commit f6f48e180404 ("lockdep: Teach lockdep about "USED" <- "IN-NMI" > inversions") overlooked that print_usage_bug() releases the graph_lock > and called it without the graph lock held. > > Fixes: f6f48e180404 ("lockdep: Teach lockdep about "USED" <- "IN-NMI" inversions") > Reported-by: Dmitry Vyukov <dvyukov@...gle.com> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org> > --- > kernel/locking/lockdep.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > --- a/kernel/locking/lockdep.c > +++ b/kernel/locking/lockdep.c > @@ -3773,7 +3773,7 @@ static void > print_usage_bug(struct task_struct *curr, struct held_lock *this, > enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit) > { > - if (!debug_locks_off_graph_unlock() || debug_locks_silent) > + if (!debug_locks_off() || debug_locks_silent) > return; > > pr_warn("\n"); > @@ -3814,6 +3814,7 @@ valid_state(struct task_struct *curr, st > enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit) > { > if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) { > + graph_unlock() > print_usage_bug(curr, this, bad_bit, new_bit); > return 0; > } I have also suspected doing unlock without a corresponding lock. This patch looks good to me. Acked-by: Waiman Long <longman@...hat.com> Cheers, Longman
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