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Subject: Re: [PATCH v2 bpf] bpf: fix lockdep false positive in stackmap
To:     Alexei Starovoitov <ast@kernel.org>, davem@davemloft.net
Cc:     peterz@infradead.org, edumazet@google.com, longman@redhat.com,
        jannh@google.com, netdev@vger.kernel.org, kernel-team@fb.com
References: <20190210205235.392478-1-ast@kernel.org>
From:   Daniel Borkmann <daniel@iogearbox.net>
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Date:   Mon, 11 Feb 2019 16:39:46 +0100
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On 02/10/2019 09:52 PM, Alexei Starovoitov wrote:
> Lockdep warns about false positive:
> [   11.211460] ------------[ cut here ]------------
> [   11.211936] DEBUG_LOCKS_WARN_ON(depth <= 0)
> [   11.211985] WARNING: CPU: 0 PID: 141 at ../kernel/locking/lockdep.c:3592 lock_release+0x1ad/0x280
> [   11.213134] Modules linked in:
> [   11.214954] RIP: 0010:lock_release+0x1ad/0x280
> [   11.223508] Call Trace:
> [   11.223705]  <IRQ>
> [   11.223874]  ? __local_bh_enable+0x7a/0x80
> [   11.224199]  up_read+0x1c/0xa0
> [   11.224446]  do_up_read+0x12/0x20
> [   11.224713]  irq_work_run_list+0x43/0x70
> [   11.225030]  irq_work_run+0x26/0x50
> [   11.225310]  smp_irq_work_interrupt+0x57/0x1f0
> [   11.225662]  irq_work_interrupt+0xf/0x20
> 
> since rw_semaphore is released in a different task vs task that locked the sema.
> It is expected behavior.
> Fix the warning with up_read_non_owner() and rwsem_release() annotation.
> 
> Fixes: bae77c5eb5b2 ("bpf: enable stackmap with build_id in nmi context")
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Applied, thanks!