From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Date: Mon, 24 Aug 2020 22:51:08 +0000 Subject: Re: [PATCHv2 net] sctp: not disable bh in the whole sctp_get_port_local() Message-Id: <20200824.155108.8657858310039234.davem@davemloft.net> List-Id: References: <08a14c2f087153c18c67965cc37ed2ac22da18ed.1597993178.git.lucien.xin@gmail.com> In-Reply-To: <08a14c2f087153c18c67965cc37ed2ac22da18ed.1597993178.git.lucien.xin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lucien.xin@gmail.com Cc: netdev@vger.kernel.org, linux-sctp@vger.kernel.org, edumazet@google.com, marcelo.leitner@gmail.com, nhorman@tuxdriver.com From: Xin Long Date: Fri, 21 Aug 2020 14:59:38 +0800 > With disabling bh in the whole sctp_get_port_local(), when > snum = 0 and too many ports have been used, the do-while > loop will take the cpu for a long time and cause cpu stuck: > > [ ] watchdog: BUG: soft lockup - CPU#11 stuck for 22s! > [ ] RIP: 0010:native_queued_spin_lock_slowpath+0x4de/0x940 > [ ] Call Trace: > [ ] _raw_spin_lock+0xc1/0xd0 > [ ] sctp_get_port_local+0x527/0x650 [sctp] > [ ] sctp_do_bind+0x208/0x5e0 [sctp] > [ ] sctp_autobind+0x165/0x1e0 [sctp] > [ ] sctp_connect_new_asoc+0x355/0x480 [sctp] > [ ] __sctp_connect+0x360/0xb10 [sctp] > > There's no need to disable bh in the whole function of > sctp_get_port_local. So fix this cpu stuck by removing > local_bh_disable() called at the beginning, and using > spin_lock_bh() instead. > > The same thing was actually done for inet_csk_get_port() in > Commit ea8add2b1903 ("tcp/dccp: better use of ephemeral > ports in bind()"). > > Thanks to Marcelo for pointing the buggy code out. > > v1->v2: > - use cond_resched() to yield cpu to other tasks if needed, > as Eric noticed. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Reported-by: Ying Xu > Signed-off-by: Xin Long Applied and queued up for -stable, thank you.