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From: Matthew Wilcox <willy@infradead.org>
To: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org, linux-mm@kvack.org,
	Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	kernel-team@fb.com, Luigi Rizzo <lrizzo@google.com>,
	Jason Gunthorpe <jgg@ziepe.ca>
Subject: Re: [PATCH bpf-next v4] bpf: fix lockdep warning triggered by stack_map_get_build_id_offset()
Date: Thu, 9 Sep 2021 14:33:15 +0100	[thread overview]
Message-ID: <YToNG9HaJYfGHusw@casper.infradead.org> (raw)
In-Reply-To: <20210909060245.2966358-1-yhs@fb.com>

On Wed, Sep 08, 2021 at 11:02:45PM -0700, Yonghong Song wrote:
> @@ -204,9 +204,10 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
>  	}
>  
>  	if (!work) {
> -		mmap_read_unlock_non_owner(current->mm);
> +		mmap_read_unlock(current->mm);
>  	} else {
>  		work->mm = current->mm;
> +		rwsem_release(&current->mm->mmap_lock.dep_map, _RET_IP_);
>  		irq_work_queue(&work->irq_work);

This needs a comment before the rwsem_release().  Something like:

		/*
		 * The lock will be released once we're out of interrupt
		 * context.  Tell lockdep that we've released it now so
		 * it doesn't complain that we forgot to release it.
		 */


  parent reply	other threads:[~2021-09-09 13:34 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-09  6:02 Yonghong Song
2021-09-09 12:34 ` Jason Gunthorpe
2021-09-09 14:54   ` Yonghong Song
2021-09-09 13:33 ` Matthew Wilcox [this message]
2021-09-09 14:55   ` Yonghong Song

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