From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Date: Thu, 20 Aug 2020 13:13:01 +0000 Subject: Re: [PATCH net] sctp: not disable bh in the whole sctp_get_port_local() Message-Id: <661ff148-627d-3b1f-f450-015dafefd137@gmail.com> List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Xin Long , network dev , linux-sctp@vger.kernel.org Cc: davem@davemloft.net, Eric Dumazet , Marcelo Ricardo Leitner , Neil Horman On 8/19/20 11:48 PM, Xin Long wrote: > 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. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Reported-by: Ying Xu > Signed-off-by: Xin Long > --- Any reason you chose to not use a cond_resched() then ? Clearly this function needs to yield, not only BH, but to other threads.