From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: Re: INFO: rcu detected stall in vprintk_emit Date: Mon, 25 Jun 2018 22:59:37 -0400 Message-ID: <20180625225937.43aee76c@vmware.local.home> References: <000000000000720530056f7f9b63@google.com> <20180626014924.GB11229@jagdpanzerIV> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: syzbot , linux-kernel@vger.kernel.org, pmladek@suse.com, sergey.senozhatsky@gmail.com, syzkaller-bugs@googlegroups.com, Samuel Ortiz , "David S. Miller" , linux-wireless@vger.kernel.org, netdev@vger.kernel.org To: Sergey Senozhatsky Return-path: In-Reply-To: <20180626014924.GB11229@jagdpanzerIV> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, 26 Jun 2018 10:49:24 +0900 Sergey Senozhatsky wrote: > So we can try switching to ratelimited error reporting > [that would be option A]: > > --- > > diff --git a/net/nfc/llcp_commands.c b/net/nfc/llcp_commands.c > index 2ceefa183cee..2f3becb709b8 100644 > --- a/net/nfc/llcp_commands.c > +++ b/net/nfc/llcp_commands.c > @@ -755,7 +755,7 @@ int nfc_llcp_send_ui_frame(struct nfc_llcp_sock *sock, u8 ssap, u8 dsap, > pdu = nfc_alloc_send_skb(sock->dev, &sock->sk, MSG_DONTWAIT, > frag_len + LLCP_HEADER_SIZE, &err); > if (pdu == NULL) { > - pr_err("Could not allocate PDU\n"); > + pr_err_ratelimited("Could not allocate PDU\n"); > continue; > } > > --- > > > Or ratelimited error reporting and cond_resched() > [that would be option B]: I don't think this is a printk() issue per se, so I think Option B is the only option. You should not get stuck in an infinite loop if we run short on memory. Perhaps we could have an Option C which would exit this loop gracefully with some kind of error. But I haven't looked at the surrounding code to be sure if that is possible. -- Steve > > --- > > diff --git a/net/nfc/llcp_commands.c b/net/nfc/llcp_commands.c > index 2ceefa183cee..61741db4c4e6 100644 > --- a/net/nfc/llcp_commands.c > +++ b/net/nfc/llcp_commands.c > @@ -755,7 +755,8 @@ int nfc_llcp_send_ui_frame(struct nfc_llcp_sock *sock, u8 ssap, u8 dsap, > pdu = nfc_alloc_send_skb(sock->dev, &sock->sk, MSG_DONTWAIT, > frag_len + LLCP_HEADER_SIZE, &err); > if (pdu == NULL) { > - pr_err("Could not allocate PDU\n"); > + pr_err_ratelimited("Could not allocate PDU\n"); > + cond_resched(); > continue; > } > > ---